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

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 Parameters


The type of the elements of source.


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.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable<TSource>. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).


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.

.NET Framework

Supported in: 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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