Статья
11/18/2011

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

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Returns an Int64 that represents the total number of elements in a sequence.

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

Syntax

'Declaration
<ExtensionAttribute> _
Public Shared Function LongCount(Of TSource) ( _
    source As IEnumerable(Of TSource) _
) As Long

public static long LongCount<TSource>(
    this IEnumerable<TSource> source
)

Type Parameters

TSource
The type of the elements of source.

Parameters

source
Type: System.Collections.Generic.IEnumerable<TSource>
An IEnumerable<T> that contains the elements to be counted.

Return Value

Type: System.Int64
The number of elements in the source 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.

Exceptions

Exception	Condition
ArgumentNullException	source is nulla null reference (Nothing in Visual Basic).
OverflowException	The number of elements exceeds MaxValue.

Remarks

Use this method rather than Count when you expect the result to be greater than MaxValue.

In Visual Basic query expression syntax, an Aggregate Into LongCount() clause translates to an invocation of LongCount.

Examples

The following code example demonstrates how to use LongCount<TSource>(IEnumerable<TSource>) to count the elements in an array.

      ' Create an array of strings.
      Dim fruits() As String = _
          {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

      ' Get the number of items in the array.
      Dim count As Long = fruits.LongCount()

      ' Display the result.
      outputBlock.Text &= "There are " & count & " fruits in the collection." & vbCrLf

      ' This code produces the following output:
      '
      ' There are 6 fruits in the collection.

      string[] fruits = { "apple", "banana", "mango", 
                               "orange", "passionfruit", "grape" };

      long count = fruits.LongCount();

      outputBlock.Text += String.Format("There are {0} fruits in the collection.", count) + "\n";

      /*
       This code produces the following output:

       There are 6 fruits in the collection.
      */

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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