Article
11/18/2011

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

Microsoft Silverlight will reach end of support after October 2021. Learn more.

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 IEnumerable(Of TSource) _
) As Integer

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

Type Parameters

TSource
The type of the elements of source.

Parameters

source
Type: System.Collections.Generic.IEnumerable<TSource>
A sequence that contains 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 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 in source is larger than MaxValue.

Remarks

If the type of source implements ICollection<T>, that implementation is used to obtain the count of elements. Otherwise, this method determines the count.

Use the LongCount method when you expect and want to allow the result to be greater than MaxValue.

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

Examples

The following code example demonstrates how to use Count<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"}

      Try
         ' Count the number of items in the array.
         Dim numberOfFruits As Integer = fruits.Count()
         ' Display the output.
         outputBlock.Text &= "There are " & numberOfFruits & " fruits in the collection." & vbCrLf
      Catch e As OverflowException
         outputBlock.Text &= "The count is too large to store as an Int32. Try using LongCount() instead." & vbCrLf
      End Try

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

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

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

      }
      catch (OverflowException)
      {
         outputBlock.Text += "The count is too large to store as an Int32." + "\n";
         outputBlock.Text += "Try using the LongCount() method instead." + "\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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