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.NET Framework Class Library

IEnumerable<T> Interface

Exposes the enumerator, which supports a simple iteration over a collection of a specified type.

To browse the .NET Framework source code for this type, see the Reference Source.

Namespace:  System.Collections.Generic
Assembly:  mscorlib (in mscorlib.dll)
Public Interface IEnumerable(Of Out T) _
	Inherits IEnumerable

Type Parameters

out T

The type of objects to enumerate.

This type parameter is covariant. That is, you can use either the type you specified or any type that is more derived. For more information about covariance and contravariance, see Covariance and Contravariance in Generics.

The IEnumerable<T> type exposes the following members.

  Name Description
Public method Supported by the XNA Framework Supported by Portable Class Library GetEnumerator Returns an enumerator that iterates through the collection.
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  Name Description
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Aggregate<TSource>(Func<TSource, TSource, TSource>) Overloaded. Applies an accumulator function over a sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Aggregate<TSource, TAccumulate>(TAccumulate, Func<TAccumulate, TSource, TAccumulate>) Overloaded. Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Aggregate<TSource, TAccumulate, TResult>(TAccumulate, Func<TAccumulate, TSource, TAccumulate>, Func<TAccumulate, TResult>) Overloaded. Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library All<TSource> Determines whether all elements of a sequence satisfy a condition. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Ancestors<T>() Overloaded. Returns a collection of elements that contains the ancestors of every node in the source collection. (Defined by Extensions.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Ancestors<T>(XName) Overloaded. Returns a filtered collection of elements that contains the ancestors of every node in the source collection. Only elements that have a matching XName are included in the collection. (Defined by Extensions.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Any<TSource>() Overloaded. Determines whether a sequence contains any elements. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Any<TSource>(Func<TSource, Boolean>) Overloaded. Determines whether any element of a sequence satisfies a condition. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library AsEnumerable<TSource> Returns the input typed as IEnumerable<T>. (Defined by Enumerable.)
Public Extension Method Supported by Portable Class Library AsParallel() Overloaded. Enables parallelization of a query. (Defined by ParallelEnumerable.)
Public Extension Method Supported by Portable Class Library AsParallel<TSource>() Overloaded. Enables parallelization of a query. (Defined by ParallelEnumerable.)
Public Extension Method Supported by Portable Class Library AsQueryable() Overloaded. Converts an IEnumerable to an IQueryable. (Defined by Queryable.)
Public Extension Method Supported by Portable Class Library AsQueryable<TElement>() Overloaded. Converts a generic IEnumerable<T> to a generic IQueryable<T>. (Defined by Queryable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Average<TSource>(Func<TSource, Decimal>) Overloaded. Computes the average of a sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Average<TSource>(Func<TSource, Nullable<Decimal>>) Overloaded. Computes the average of a sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Average<TSource>(Func<TSource, Double>) Overloaded. Computes the average of a sequence of Double values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Average<TSource>(Func<TSource, Nullable<Double>>) Overloaded. Computes the average of a sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Average<TSource>(Func<TSource, Int32>) Overloaded. Computes the average of a sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Average<TSource>(Func<TSource, Nullable<Int32>>) Overloaded. Computes the average of a sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Average<TSource>(Func<TSource, Int64>) Overloaded. Computes the average of a sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Average<TSource>(Func<TSource, Nullable<Int64>>) Overloaded. Computes the average of a sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Average<TSource>(Func<TSource, Single>) Overloaded. Computes the average of a sequence of Single values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Average<TSource>(Func<TSource, Nullable<Single>>) Overloaded. Computes the average of a sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Cast<TResult> Casts the elements of an IEnumerable to the specified type. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Concat<TSource> Concatenates two sequences. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Contains<TSource>(TSource) Overloaded. Determines whether a sequence contains a specified element by using the default equality comparer. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Contains<TSource>(TSource, IEqualityComparer<TSource>) Overloaded. Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>. (Defined by Enumerable.)
Public Extension Method CopyToDataTable<T>() Overloaded. Returns a DataTable that contains copies of the DataRow objects, given an input IEnumerable<T> object where the generic parameter T is DataRow. (Defined by DataTableExtensions.)
Public Extension Method CopyToDataTable<T>(DataTable, LoadOption) Overloaded. Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow. (Defined by DataTableExtensions.)
Public Extension Method CopyToDataTable<T>(DataTable, LoadOption, FillErrorEventHandler) Overloaded. Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow. (Defined by DataTableExtensions.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Count<TSource>() Overloaded. Returns the number of elements in a sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Count<TSource>(Func<TSource, Boolean>) Overloaded. Returns a number that represents how many elements in the specified sequence satisfy a condition. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library DefaultIfEmpty<TSource>() Overloaded. Returns the elements of the specified sequence or the type parameter's default value in a singleton collection if the sequence is empty. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library DefaultIfEmpty<TSource>(TSource) Overloaded. Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library DescendantNodes<T> Returns a collection of the descendant nodes of every document and element in the source collection. (Defined by Extensions.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Descendants<T>() Overloaded. Returns a collection of elements that contains the descendant elements of every element and document in the source collection. (Defined by Extensions.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Descendants<T>(XName) Overloaded. Returns a filtered collection of elements that contains the descendant elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection. (Defined by Extensions.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Distinct<TSource>() Overloaded. Returns distinct elements from a sequence by using the default equality comparer to compare values. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Distinct<TSource>(IEqualityComparer<TSource>) Overloaded. Returns distinct elements from a sequence by using a specified IEqualityComparer<T> to compare values. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library ElementAt<TSource> Returns the element at a specified index in a sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library ElementAtOrDefault<TSource> Returns the element at a specified index in a sequence or a default value if the index is out of range. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Elements<T>() Overloaded. Returns a collection of the child elements of every element and document in the source collection. (Defined by Extensions.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Elements<T>(XName) Overloaded. Returns a filtered collection of the child elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection. (Defined by Extensions.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Except<TSource>(IEnumerable<TSource>) Overloaded. Produces the set difference of two sequences by using the default equality comparer to compare values. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Except<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>) Overloaded. Produces the set difference of two sequences by using the specified IEqualityComparer<T> to compare values. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library First<TSource>() Overloaded. Returns the first element of a sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library First<TSource>(Func<TSource, Boolean>) Overloaded. Returns the first element in a sequence that satisfies a specified condition. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library FirstOrDefault<TSource>() Overloaded. Returns the first element of a sequence, or a default value if the sequence contains no elements. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library FirstOrDefault<TSource>(Func<TSource, Boolean>) Overloaded. Returns the first element of the sequence that satisfies a condition or a default value if no such element is found. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library GroupBy<TSource, TKey>(Func<TSource, TKey>) Overloaded. Groups the elements of a sequence according to a specified key selector function. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library GroupBy<TSource, TKey>(Func<TSource, TKey>, IEqualityComparer<TKey>) Overloaded. Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library GroupBy<TSource, TKey, TElement>(Func<TSource, TKey>, Func<TSource, TElement>) Overloaded. Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library GroupBy<TSource, TKey, TResult>(Func<TSource, TKey>, Func<TKey, IEnumerable<TSource>, TResult>) Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library GroupBy<TSource, TKey, TElement>(Func<TSource, TKey>, Func<TSource, TElement>, IEqualityComparer<TKey>) Overloaded. Groups the elements of a sequence according to a key selector function. The keys are compared by using a comparer and each group's elements are projected by using a specified function. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library GroupBy<TSource, TKey, TResult>(Func<TSource, TKey>, Func<TKey, IEnumerable<TSource>, TResult>, IEqualityComparer<TKey>) Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The keys are compared by using a specified comparer. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library GroupBy<TSource, TKey, TElement, TResult>(Func<TSource, TKey>, Func<TSource, TElement>, Func<TKey, IEnumerable<TElement>, TResult>) Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The elements of each group are projected by using a specified function. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library GroupBy<TSource, TKey, TElement, TResult>(Func<TSource, TKey>, Func<TSource, TElement>, Func<TKey, IEnumerable<TElement>, TResult>, IEqualityComparer<TKey>) Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library GroupJoin<TOuter, TInner, TKey, TResult>(IEnumerable<TInner>, Func<TOuter, TKey>, Func<TInner, TKey>, Func<TOuter, IEnumerable<TInner>, TResult>) Overloaded. Correlates the elements of two sequences based on equality of keys and groups the results. The default equality comparer is used to compare keys. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library GroupJoin<TOuter, TInner, TKey, TResult>(IEnumerable<TInner>, Func<TOuter, TKey>, Func<TInner, TKey>, Func<TOuter, IEnumerable<TInner>, TResult>, IEqualityComparer<TKey>) Overloaded. Correlates the elements of two sequences based on key equality and groups the results. A specified IEqualityComparer<T> is used to compare keys. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library InDocumentOrder<T> Returns a collection of nodes that contains all nodes in the source collection, sorted in document order. (Defined by Extensions.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Intersect<TSource>(IEnumerable<TSource>) Overloaded. Produces the set intersection of two sequences by using the default equality comparer to compare values. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Intersect<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>) Overloaded. Produces the set intersection of two sequences by using the specified IEqualityComparer<T> to compare values. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Join<TOuter, TInner, TKey, TResult>(IEnumerable<TInner>, Func<TOuter, TKey>, Func<TInner, TKey>, Func<TOuter, TInner, TResult>) Overloaded. Correlates the elements of two sequences based on matching keys. The default equality comparer is used to compare keys. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Join<TOuter, TInner, TKey, TResult>(IEnumerable<TInner>, Func<TOuter, TKey>, Func<TInner, TKey>, Func<TOuter, TInner, TResult>, IEqualityComparer<TKey>) Overloaded. Correlates the elements of two sequences based on matching keys. A specified IEqualityComparer<T> is used to compare keys. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Last<TSource>() Overloaded. Returns the last element of a sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Last<TSource>(Func<TSource, Boolean>) Overloaded. Returns the last element of a sequence that satisfies a specified condition. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library LastOrDefault<TSource>() Overloaded. Returns the last element of a sequence, or a default value if the sequence contains no elements. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library LastOrDefault<TSource>(Func<TSource, Boolean>) Overloaded. Returns the last element of a sequence that satisfies a condition or a default value if no such element is found. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library LongCount<TSource>() Overloaded. Returns an Int64 that represents the total number of elements in a sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library LongCount<TSource>(Func<TSource, Boolean>) Overloaded. Returns an Int64 that represents how many elements in a sequence satisfy a condition. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Max<TSource>() Overloaded. Returns the maximum value in a generic sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Max<TSource>(Func<TSource, Decimal>) Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Decimal value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Max<TSource>(Func<TSource, Nullable<Decimal>>) Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Decimal value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Max<TSource>(Func<TSource, Double>) Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Double value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Max<TSource>(Func<TSource, Nullable<Double>>) Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Double value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Max<TSource>(Func<TSource, Int32>) Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int32 value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Max<TSource>(Func<TSource, Nullable<Int32>>) Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int32 value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Max<TSource>(Func<TSource, Int64>) Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int64 value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Max<TSource>(Func<TSource, Nullable<Int64>>) Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int64 value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Max<TSource>(Func<TSource, Single>) Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Single value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Max<TSource>(Func<TSource, Nullable<Single>>) Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Single value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Max<TSource, TResult>(Func<TSource, TResult>) Overloaded. Invokes a transform function on each element of a generic sequence and returns the maximum resulting value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Min<TSource>() Overloaded. Returns the minimum value in a generic sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Min<TSource>(Func<TSource, Decimal>) Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Decimal value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Min<TSource>(Func<TSource, Nullable<Decimal>>) Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Decimal value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Min<TSource>(Func<TSource, Double>) Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Double value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Min<TSource>(Func<TSource, Nullable<Double>>) Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Double value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Min<TSource>(Func<TSource, Int32>) Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int32 value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Min<TSource>(Func<TSource, Nullable<Int32>>) Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int32 value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Min<TSource>(Func<TSource, Int64>) Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int64 value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Min<TSource>(Func<TSource, Nullable<Int64>>) Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int64 value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Min<TSource>(Func<TSource, Single>) Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Single value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Min<TSource>(Func<TSource, Nullable<Single>>) Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Single value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Min<TSource, TResult>(Func<TSource, TResult>) Overloaded. Invokes a transform function on each element of a generic sequence and returns the minimum resulting value. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Nodes<T> Returns a collection of the child nodes of every document and element in the source collection. (Defined by Extensions.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library OfType<TResult> Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library OrderBy<TSource, TKey>(Func<TSource, TKey>) Overloaded. Sorts the elements of a sequence in ascending order according to a key. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library OrderBy<TSource, TKey>(Func<TSource, TKey>, IComparer<TKey>) Overloaded. Sorts the elements of a sequence in ascending order by using a specified comparer. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library OrderByDescending<TSource, TKey>(Func<TSource, TKey>) Overloaded. Sorts the elements of a sequence in descending order according to a key. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library OrderByDescending<TSource, TKey>(Func<TSource, TKey>, IComparer<TKey>) Overloaded. Sorts the elements of a sequence in descending order by using a specified comparer. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Remove<T> Removes every node in the source collection from its parent node. (Defined by Extensions.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Reverse<TSource> Inverts the order of the elements in a sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Select<TSource, TResult>(Func<TSource, TResult>) Overloaded. Projects each element of a sequence into a new form. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Select<TSource, TResult>(Func<TSource, Int32, TResult>) Overloaded. Projects each element of a sequence into a new form by incorporating the element's index. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library SelectMany<TSource, TResult>(Func<TSource, IEnumerable<TResult>>) Overloaded. Projects each element of a sequence to an IEnumerable<T> and flattens the resulting sequences into one sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library SelectMany<TSource, TResult>(Func<TSource, Int32, IEnumerable<TResult>>) Overloaded. Projects each element of a sequence to an IEnumerable<T>, and flattens the resulting sequences into one sequence. The index of each source element is used in the projected form of that element. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library SelectMany<TSource, TCollection, TResult>(Func<TSource, Int32, IEnumerable<TCollection>>, Func<TSource, TCollection, TResult>) Overloaded. Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. The index of each source element is used in the intermediate projected form of that element. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library SelectMany<TSource, TCollection, TResult>(Func<TSource, IEnumerable<TCollection>>, Func<TSource, TCollection, TResult>) Overloaded. Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library SequenceEqual<TSource>(IEnumerable<TSource>) Overloaded. Determines whether two sequences are equal by comparing the elements by using the default equality comparer for their type. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library SequenceEqual<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>) Overloaded. Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer<T>. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Single<TSource>() Overloaded. Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Single<TSource>(Func<TSource, Boolean>) Overloaded. Returns the only element of a sequence that satisfies a specified condition, and throws an exception if more than one such element exists. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library SingleOrDefault<TSource>() Overloaded. Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library SingleOrDefault<TSource>(Func<TSource, Boolean>) Overloaded. Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Skip<TSource> Bypasses a specified number of elements in a sequence and then returns the remaining elements. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library SkipWhile<TSource>(Func<TSource, Boolean>) Overloaded. Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library SkipWhile<TSource>(Func<TSource, Int32, Boolean>) Overloaded. Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. The element's index is used in the logic of the predicate function. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Sum<TSource>(Func<TSource, Decimal>) Overloaded. Computes the sum of the sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Sum<TSource>(Func<TSource, Nullable<Decimal>>) Overloaded. Computes the sum of the sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Sum<TSource>(Func<TSource, Double>) Overloaded. Computes the sum of the sequence of Double values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Sum<TSource>(Func<TSource, Nullable<Double>>) Overloaded. Computes the sum of the sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Sum<TSource>(Func<TSource, Int32>) Overloaded. Computes the sum of the sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Sum<TSource>(Func<TSource, Nullable<Int32>>) Overloaded. Computes the sum of the sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Sum<TSource>(Func<TSource, Int64>) Overloaded. Computes the sum of the sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Sum<TSource>(Func<TSource, Nullable<Int64>>) Overloaded. Computes the sum of the sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Sum<TSource>(Func<TSource, Single>) Overloaded. Computes the sum of the sequence of Single values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Sum<TSource>(Func<TSource, Nullable<Single>>) Overloaded. Computes the sum of the sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Take<TSource> Returns a specified number of contiguous elements from the start of a sequence. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library TakeWhile<TSource>(Func<TSource, Boolean>) Overloaded. Returns elements from a sequence as long as a specified condition is true. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library TakeWhile<TSource>(Func<TSource, Int32, Boolean>) Overloaded. Returns elements from a sequence as long as a specified condition is true. The element's index is used in the logic of the predicate function. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library ToArray<TSource> Creates an array from a IEnumerable<T>. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library ToDictionary<TSource, TKey>(Func<TSource, TKey>) Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library ToDictionary<TSource, TKey>(Func<TSource, TKey>, IEqualityComparer<TKey>) Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function and key comparer. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library ToDictionary<TSource, TKey, TElement>(Func<TSource, TKey>, Func<TSource, TElement>) Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to specified key selector and element selector functions. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library ToDictionary<TSource, TKey, TElement>(Func<TSource, TKey>, Func<TSource, TElement>, IEqualityComparer<TKey>) Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function, a comparer, and an element selector function. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library ToList<TSource> Creates a List<T> from an IEnumerable<T>. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library ToLookup<TSource, TKey>(Func<TSource, TKey>) Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library ToLookup<TSource, TKey>(Func<TSource, TKey>, IEqualityComparer<TKey>) Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function and key comparer. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library ToLookup<TSource, TKey, TElement>(Func<TSource, TKey>, Func<TSource, TElement>) Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to specified key selector and element selector functions. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library ToLookup<TSource, TKey, TElement>(Func<TSource, TKey>, Func<TSource, TElement>, IEqualityComparer<TKey>) Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function, a comparer and an element selector function. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Union<TSource>(IEnumerable<TSource>) Overloaded. Produces the set union of two sequences by using the default equality comparer. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Union<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>) Overloaded. Produces the set union of two sequences by using a specified IEqualityComparer<T>. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Where<TSource>(Func<TSource, Boolean>) Overloaded. Filters a sequence of values based on a predicate. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework Supported by Portable Class Library Where<TSource>(Func<TSource, Int32, Boolean>) Overloaded. Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function. (Defined by Enumerable.)
Public Extension Method Supported by Portable Class Library Zip<TFirst, TSecond, TResult> Applies a specified function to the corresponding elements of two sequences, producing a sequence of the results. (Defined by Enumerable.)
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Note Note

To view the .NET Framework source code for this type, see the Reference Source. You can browse through the source code online, download the reference for offline viewing, and step through the sources (including patches and updates) during debugging; see instructions.

IEnumerable<T> is the base interface for collections in the System.Collections.Generic namespace such as List<T>, Dictionary<TKey, TValue>, and Stack<T> and other generic collections such as ObservableCollection<T> and ConcurrentStack<T>. Collections that implement IEnumerable<T> can be enumerated by using the foreach statement.

For the non-generic version of this interface, see System.Collections.IEnumerable.

IEnumerable<T> contains a single method that you must implement when implementing this interface; GetEnumerator, which returns an IEnumerator<T> object. The returned IEnumerator<T> provides the ability to iterate through the collection by exposing a Current property.

Notes to Implementers

IEnumerable<T> is included for parity with non-generic collections; implementing IEnumerable<T> allows a generic collection to be passed to a method that expects an IEnumerable object.

The following example demonstrates how to implement the IEnumerable<T> interface and how to use that implementation to create a LINQ query. When you implement IEnumerable<T>, you must also implement IEnumerator<T> or, for C# only, you can use the yield (C# Reference) keyword. Implementing IEnumerator<T> also requires IDisposable to be implemented, which you will see in this example.

Option Strict On 
Public Class App
    ' Excercise the Iterator and show that it's more 
    ' performant. 
    Public Shared Sub Main()
        TestStreamReaderEnumerable()
        TestReadingFile()
    End Sub 

    Shared Sub TestStreamReaderEnumerable()
        ' Check the memory before the iterator is used. 
        Dim memoryBefore = GC.GetTotalMemory(True)

        ' Open a file with the StreamReaderEnumerable and check for a string. 
        Dim stringsFound =
            From line In New StreamReaderEnumerable("c:\temp\tempFile.txt")
            Where line.Contains("string to search for")

        Console.WriteLine("Found:" & stringsFound.Count())

        ' Check the memory after the iterator and output it to the console. 
        Dim memoryAfter = GC.GetTotalMemory(False)
        Console.WriteLine("Memory Used With Iterator = " & vbTab & Format((memoryAfter - memoryBefore) / 1000, "n") & "kb")
    End Sub 

    Shared Sub TestReadingFile()
        Dim memoryBefore = GC.GetTotalMemory(True)

        ' Open a file with a regular file reader. 
        Dim sr = My.Computer.FileSystem.OpenTextFileReader("c:\temp\tempFile.txt")

        ' Add the file contents to a generic list of strings. 
        Dim fileContents As New List(Of String)
        While Not sr.EndOfStream
            fileContents.Add(sr.ReadLine())
        End While 

        ' Check for the string. 
        Dim stringsFound =
            From line In fileContents
            Where line.Contains("string to search for")

        sr.Close()
        Console.WriteLine("Found: " & stringsFound.Count())
        ' Check the memory after when the iterator is not used, and output it to the console. 
        Dim memoryAfter = GC.GetTotalMemory(False)
        Console.WriteLine("Memory Used Without Iterator = " &
                          vbTab & Format((memoryAfter - memoryBefore) / 1000, "n") & "kb")

    End Sub 
End Class 

' A custom class that implements IEnumerable(T). When you implement IEnumerable(T),  
' you must also implement IEnumerable and IEnumerator(T). 
Public Class StreamReaderEnumerable
    Implements IEnumerable(Of String)

    Private _filePath As String 

    Public Sub New(ByVal filePath As String)
        _filePath = filePath
    End Sub 


    ' Must implement GetEnumerator, which returns a new StreamReaderEnumerator. 
    Public Function GetEnumerator() As IEnumerator(Of String) _
        Implements IEnumerable(Of String).GetEnumerator

        Return New StreamReaderEnumerator(_filePath)
    End Function 

    ' Must also implement IEnumerable.GetEnumerator, but implement as a private method. 
    Private Function GetEnumerator1() As IEnumerator _
        Implements IEnumerable.GetEnumerator

        Return Me.GetEnumerator()
    End Function 

End Class 

' When you implement IEnumerable(T), you must also implement IEnumerator(T),  
' which will walk through the contents of the file one line at a time. 
' Implementing IEnumerator(T) requires that you implement IEnumerator and IDisposable. 
Public Class StreamReaderEnumerator
    Implements IEnumerator(Of String)

    Private _sr As IO.StreamReader

    Public Sub New(ByVal filePath As String)
        _sr = New IO.StreamReader(filePath)
    End Sub 

    Private _current As String 

    ' Implement the IEnumerator(T).Current publicly, but implement  
    ' IEnumerator.Current, which is also required, privately. 
    Public ReadOnly Property Current() As String _
        Implements IEnumerator(Of String).Current

        Get 
            If _sr Is Nothing OrElse _current Is Nothing Then 
                Throw New InvalidOperationException()
            End If 

            Return _current
        End Get 
    End Property 


    Private ReadOnly Property Current1() As Object _
        Implements IEnumerator.Current

        Get 
            Return Me.Current
        End Get 
    End Property 

    ' Implement MoveNext and Reset, which are required by IEnumerator. 
    Public Function MoveNext() As Boolean _
        Implements System.Collections.IEnumerator.MoveNext

        _current = _sr.ReadLine()
        If _current Is Nothing Then Return False 
        Return True 
    End Function 

    Public Sub Reset() _
        Implements System.Collections.IEnumerator.Reset

        _sr.DiscardBufferedData()
        _sr.BaseStream.Seek(0, IO.SeekOrigin.Begin)
        _current = Nothing 
    End Sub 

    ' Implement IDisposable, which is also implemented by IEnumerator(T). 
    Private disposedValue As Boolean = False 

    Public Sub Dispose() Implements IDisposable.Dispose
        Dispose(True)
        GC.SuppressFinalize(Me)
    End Sub 
    Protected Overridable Sub Dispose(ByVal disposing As Boolean)
        If Not Me.disposedValue Then 
            If disposing Then 
                ' Dispose of managed resources. 
            End If
            _current = Nothing
            _sr.Close()
            _sr.Dispose()
        End If 

        Me.disposedValue = True 
    End Sub 

    Protected Overrides Sub Finalize()
        Dispose(False)
    End Sub 

End Class 
' This example displays output similar to the following: 
' Found:2 
' Memory Used With Iterator =     32.77kb 
' Found: 2 
' Memory Used Without Iterator =  37.94kb

For another C# example that demonstrates how to implement the IEnumerable<T> interface, see the Generics Sample. This sample uses the yield keyword instead of implementing IEnumerator<T>.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8