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Enumerable.First<TSource> Method (IEnumerable<TSource>)

April 12, 2014

Returns the first element of a sequence.

Namespace:  System.Linq
Assembly:  System.Core (in System.Core.dll)
public static TSource First<TSource>(
	this IEnumerable<TSource> source
)

Type Parameters

TSource

The type of the elements of source.

Parameters

source
Type: System.Collections.Generic.IEnumerable<TSource>
The IEnumerable<T> to return the first element of.

Return Value

Type: TSource
The first element in the specified sequence.

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.
ExceptionCondition
ArgumentNullException

source is null.

InvalidOperationException

The source sequence is empty.

The First<TSource>(IEnumerable<TSource>) method throws an exception if source contains no elements. To instead return a default value when the source sequence is empty, use the FirstOrDefault method.

The following code example demonstrates how to use First<TSource>(IEnumerable<TSource>) to return the first element of an array.


      int[] numbers = { 9, 34, 65, 92, 87, 435, 3, 54, 
                             83, 23, 87, 435, 67, 12, 19 };

      int first = numbers.First();

      outputBlock.Text += first + "\n";

      /*
       This code produces the following output:

       9
      */



Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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