Enumerable.FirstOrDefault<TSource> Method (IEnumerable<TSource>, Func<TSource, Boolean>)


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Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)

public static TSource FirstOrDefault<TSource>(
	this IEnumerable<TSource> source,
	Func<TSource, bool> predicate


Type: System.Collections.Generic.IEnumerable<TSource>

An IEnumerable<T> to return an element from.

Type: System.Func<TSource, Boolean>

A function to test each element for a condition.

Return Value

Type: TSource

default(TSource) if source is empty or if no element passes the test specified by predicate; otherwise, the first element in source that passes the test specified by predicate.

Type Parameters


The type of the elements of source.

Exception Condition

source or predicate is null.

The default value for reference and nullable types is null.

The following code example demonstrates how to use FirstOrDefault<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>) by passing in a predicate. In the second call to the method, there is no element in the array that satisfies the condition.

string[] names = { "Hartono, Tommy", "Adams, Terry", 
                     "Andersen, Henriette Thaulow", 
                     "Hedlund, Magnus", "Ito, Shu" };

string firstLongName = names.FirstOrDefault(name => name.Length > 20);

Console.WriteLine("The first long name is '{0}'.", firstLongName);

string firstVeryLongName = names.FirstOrDefault(name => name.Length > 30);

    "There is {0} name longer than 30 characters.",
    string.IsNullOrEmpty(firstVeryLongName) ? "not a" : "a");

 This code produces the following output:

 The first long name is 'Andersen, Henriette Thaulow'.
 There is not a name longer than 30 characters.

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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