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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.

Name Description
System_CAPS_pubmethod GetEnumerator()

Returns an enumerator that iterates through the collection.

Name Description
System_CAPS_pubmethod Aggregate<TSource>(Func<TSource, TSource, TSource>)

Overloaded. Applies an accumulator function over a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod All<TSource>(Func<TSource, Boolean>)

Determines whether all elements of a sequence satisfy a condition.(Defined by Enumerable.)

System_CAPS_pubmethod Ancestors<T>()

Overloaded. Returns a collection of elements that contains the ancestors of every node in the source collection.(Defined by Extensions.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod Any<TSource>()

Overloaded. Determines whether a sequence contains any elements.(Defined by Enumerable.)

System_CAPS_pubmethod Any<TSource>(Func<TSource, Boolean>)

Overloaded. Determines whether any element of a sequence satisfies a condition.(Defined by Enumerable.)

System_CAPS_pubmethod AsEnumerable<TSource>()

Returns the input typed as IEnumerable<T>.(Defined by Enumerable.)

System_CAPS_pubmethod AsParallel<TSource>()

Overloaded. Enables parallelization of a query.(Defined by ParallelEnumerable.)

System_CAPS_pubmethod AsQueryable<TElement>()

Overloaded. Converts a generic IEnumerable<T> to a generic IQueryable<T>.(Defined by Queryable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod Cast<TResult>()

Casts the elements of an IEnumerable to the specified type.(Defined by Enumerable.)

System_CAPS_pubmethod Concat<TSource>(IEnumerable<TSource>)

Concatenates two sequences.(Defined by Enumerable.)

System_CAPS_pubmethod Contains<TSource>(TSource)

Overloaded. Determines whether a sequence contains a specified element by using the default equality comparer.(Defined by Enumerable.)

System_CAPS_pubmethod Contains<TSource>(TSource, IEqualityComparer<TSource>)

Overloaded. Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod Count<TSource>()

Overloaded. Returns the number of elements in a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Count<TSource>(Func<TSource, Boolean>)

Overloaded. Returns a number that represents how many elements in the specified sequence satisfy a condition.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod DescendantNodes<T>()

Returns a collection of the descendant nodes of every document and element in the source collection.(Defined by Extensions.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod Distinct<TSource>()

Overloaded. Returns distinct elements from a sequence by using the default equality comparer to compare values.(Defined by Enumerable.)

System_CAPS_pubmethod Distinct<TSource>(IEqualityComparer<TSource>)

Overloaded. Returns distinct elements from a sequence by using a specified IEqualityComparer<T> to compare values.(Defined by Enumerable.)

System_CAPS_pubmethod ElementAt<TSource>(Int32)

Returns the element at a specified index in a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod ElementAtOrDefault<TSource>(Int32)

Returns the element at a specified index in a sequence or a default value if the index is out of range.(Defined by Enumerable.)

System_CAPS_pubmethod Elements<T>()

Overloaded. Returns a collection of the child elements of every element and document in the source collection.(Defined by Extensions.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod Except<TSource>(IEnumerable<TSource>)

Overloaded. Produces the set difference of two sequences by using the default equality comparer to compare values.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod First<TSource>()

Overloaded. Returns the first element of a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod First<TSource>(Func<TSource, Boolean>)

Overloaded. Returns the first element in a sequence that satisfies a specified condition.(Defined by Enumerable.)

System_CAPS_pubmethod FirstOrDefault<TSource>()

Overloaded. Returns the first element of a sequence, or a default value if the sequence contains no elements.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod GroupBy<TSource, TKey>(Func<TSource, TKey>)

Overloaded. Groups the elements of a sequence according to a specified key selector function.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod InDocumentOrder<T>()

Returns a collection of nodes that contains all nodes in the source collection, sorted in document order.(Defined by Extensions.)

System_CAPS_pubmethod Intersect<TSource>(IEnumerable<TSource>)

Overloaded. Produces the set intersection of two sequences by using the default equality comparer to compare values.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod Last<TSource>()

Overloaded. Returns the last element of a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Last<TSource>(Func<TSource, Boolean>)

Overloaded. Returns the last element of a sequence that satisfies a specified condition.(Defined by Enumerable.)

System_CAPS_pubmethod LastOrDefault<TSource>()

Overloaded. Returns the last element of a sequence, or a default value if the sequence contains no elements.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod LongCount<TSource>()

Overloaded. Returns an Int64 that represents the total number of elements in a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod LongCount<TSource>(Func<TSource, Boolean>)

Overloaded. Returns an Int64 that represents how many elements in a sequence satisfy a condition.(Defined by Enumerable.)

System_CAPS_pubmethod Max<TSource>()

Overloaded. Returns the maximum value in a generic sequence.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod Min<TSource>()

Overloaded. Returns the minimum value in a generic sequence.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod Nodes<T>()

Returns a collection of the child nodes of every document and element in the source collection.(Defined by Extensions.)

System_CAPS_pubmethod OfType<TResult>()

Filters the elements of an IEnumerable based on a specified type.(Defined by Enumerable.)

System_CAPS_pubmethod OrderBy<TSource, TKey>(Func<TSource, TKey>)

Overloaded. Sorts the elements of a sequence in ascending order according to a key.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod OrderByDescending<TSource, TKey>(Func<TSource, TKey>)

Overloaded. Sorts the elements of a sequence in descending order according to a key.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod Remove<T>()

Overloaded. Removes every node in the source collection from its parent node.(Defined by Extensions.)

System_CAPS_pubmethod Reverse<TSource>()

Inverts the order of the elements in a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Select<TSource, TResult>(Func<TSource, TResult>)

Overloaded. Projects each element of a sequence into a new form.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod Skip<TSource>(Int32)

Bypasses a specified number of elements in a sequence and then returns the remaining elements.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod Take<TSource>(Int32)

Returns a specified number of contiguous elements from the start of a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod TakeWhile<TSource>(Func<TSource, Boolean>)

Overloaded. Returns elements from a sequence as long as a specified condition is true.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod ToArray<TSource>()

Creates an array from a IEnumerable<T>.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod ToList<TSource>()

Creates a List<T> from an IEnumerable<T>.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod Union<TSource>(IEnumerable<TSource>)

Overloaded. Produces the set union of two sequences by using the default equality comparer.(Defined by Enumerable.)

System_CAPS_pubmethod Union<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)

Overloaded. Produces the set union of two sequences by using a specified IEqualityComparer<T>.(Defined by Enumerable.)

System_CAPS_pubmethod Where<TSource>(Func<TSource, Boolean>)

Overloaded. Filters a sequence of values based on a predicate.(Defined by Enumerable.)

System_CAPS_pubmethod 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.)

System_CAPS_pubmethod Zip<TFirst, TSecond, TResult>(IEnumerable<TSecond>, Func<TFirst, TSecond, TResult>)

Applies a specified function to the corresponding elements of two sequences, producing a sequence of the results.(Defined by Enumerable.)

System_CAPS_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.

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.

Imports System.IO
Imports System.Collections
Imports System.Collections.Generic
Imports System.Linq

Public Module App
   ' Excercise the Iterator and show that it's more performant.
   Public Sub Main()
      TestStreamReaderEnumerable()
      Console.WriteLine("---")
      TestReadingFile()
   End Sub

   Public Sub TestStreamReaderEnumerable()
		' Check the memory before the iterator is used.
		Dim memoryBefore As Long = GC.GetTotalMemory(true)
      Dim stringsFound As IEnumerable(Of String)
		' Open a file with the StreamReaderEnumerable and check for a string.
      Try
         stringsFound =
               from line in new StreamReaderEnumerable("c:\temp\tempFile.txt")
               where line.Contains("string to search for")
               select line
         Console.WriteLine("Found: {0}", stringsFound.Count())
      Catch e As FileNotFoundException
         Console.WriteLine("This example requires a file named C:\temp\tempFile.txt.")
         Return
      End Try

		' Check the memory after the iterator and output it to the console.
		Dim memoryAfter As Long = GC.GetTotalMemory(false)
		Console.WriteLine("Memory Used with Iterator = {1}{0} kb",
                        (memoryAfter - memoryBefore)\1000, vbTab)
   End Sub

   Public Sub TestReadingFile()
		Dim memoryBefore As Long = GC.GetTotalMemory(true)
      Dim sr As StreamReader
      Try
         sr = File.OpenText("c:\temp\tempFile.txt")
      Catch e As FileNotFoundException
         Console.WriteLine("This example requires a file named C:\temp\tempFile.txt.")
         Return
      End Try

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

		' Check for the string.
		Dim stringsFound =
            from line in fileContents
            where line.Contains("string to search for")
            select line

      sr.Close()
      Console.WriteLine("Found: {0}", stringsFound.Count())

		' Check the memory after when the iterator is not used, and output it to the console.
		Dim memoryAfter As Long = GC.GetTotalMemory(False)
		Console.WriteLine("Memory Used without Iterator = {1}{0} kb",
                        (memoryAfter - memoryBefore)\1000, vbTab)
   End Sub
End Module

' 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(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 StreamReader

    Public Sub New(filePath As String)
        _sr = New 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
                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 IEnumerator.MoveNext
        _current = _sr.ReadLine()
        if _current Is Nothing Then Return False

        Return True
    End Function

    Public Sub Reset() _
          Implements IEnumerator.Reset
        _sr.DiscardBufferedData()
        _sr.BaseStream.Seek(0, 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(disposing As Boolean)
        If Not Me.disposedValue Then
            If disposing Then
                ' Dispose of managed resources.
            End If

            _current = Nothing
            If _sr IsNot Nothing Then
               _sr.Close()
               _sr.Dispose()
            End If
        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 =     33kb
'       ---
'       Found: 2
'       Memory Used Without Iterator =  206kb

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>.

Universal Windows Platform
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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