Статья
11/17/2011

Queryable.Count<TSource> Method (IQueryable<TSource>)

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Returns the number of elements in a sequence.

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

Syntax

'Declaration
<ExtensionAttribute> _
Public Shared Function Count(Of TSource) ( _
    source As IQueryable(Of TSource) _
) As Integer

public static int Count<TSource>(
    this IQueryable<TSource> source
)

Type Parameters

TSource
The type of the elements of source.

Parameters

source
Type: System.Linq.IQueryable<TSource>
The IQueryable<T> that contains the elements to be counted.

Return Value

Type: System.Int32
The number of elements in the input sequence.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IQueryable<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 in source is larger than MaxValue.

Remarks

The Count<TSource>(IQueryable<TSource>) method generates a MethodCallExpression that represents calling Count<TSource>(IQueryable<TSource>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Count<TSource>(IQueryable<TSource>) depends on the implementation of the type of the source parameter. The expected behavior is that it counts the number of items in source.

Examples

The following code example demonstrates how to use Count<TSource>(IQueryable<TSource>) to count the elements in a sequence.

      Dim fruits() As String = {"apple", "banana", "mango", _
                          "orange", "passionfruit", "grape"}

      Dim numberOfFruits As Integer = fruits.AsQueryable().Count()

      outputBlock.Text &= String.Format( _
          "There are {0} items in the array.", _
          numberOfFruits) & vbCrLf

      ' This code produces the following output:
      '
      ' There are 6 items in the array.

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

         int numberOfFruits = fruits.AsQueryable().Count();

         outputBlock.Text += String.Format(
             "There are {0} items in the array.",
             numberOfFruits) + "\n";

         // This code produces the following output:
         //
         // There are 6 items in the array.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1

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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