Article
11/18/2011

Queryable.Contains<TSource> Method (IQueryable<TSource>, TSource)

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Determines whether a sequence contains a specified element by using the default equality comparer.

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

Syntax

'Declaration
<ExtensionAttribute> _
Public Shared Function Contains(Of TSource) ( _
    source As IQueryable(Of TSource), _
    item As TSource _
) As Boolean

public static bool Contains<TSource>(
    this IQueryable<TSource> source,
    TSource item
)

Type Parameters

TSource
The type of the elements of source.

Parameters

source
Type: System.Linq.IQueryable<TSource>
An IQueryable<T> in which to locate item.

item
Type: TSource
The object to locate in the sequence.

Return Value

Type: System.Boolean
true if the input sequence contains an element that has the specified value; otherwise, false.

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).

Remarks

The Contains<TSource>(IQueryable<TSource>, TSource) method generates a MethodCallExpression that represents calling Contains<TSource>(IQueryable<TSource>, 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 Contains<TSource>(IQueryable<TSource>, TSource) depends on the implementation of the type of the source parameter. The expected behavior is that it determines if source contains item.

Examples

The following code example demonstrates how to use Contains<TSource>(IQueryable<TSource>, TSource) to determine whether a sequence contains a specific element.

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

      ' The string to search for in the array.
      Dim mango As String = "mango"

      Dim hasMango As Boolean = fruits.AsQueryable().Contains(mango)

      outputBlock.Text &= String.Format("The array {0} contain '{1}'.", _
              IIf(hasMango, "does", "does not"), mango) & vbCrLf

      ' This code produces the following output:
      '
      ' The array does contain 'mango'.

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

         // The string to search for in the array.
         string mango = "mango";

         bool hasMango = fruits.AsQueryable().Contains(mango);

         outputBlock.Text += String.Format(
             "The array {0} contain '{1}'.",
             hasMango ? "does" : "does not",
             mango) + "\n";

         // This code produces the following output:
         //
         // The array does contain 'mango'.

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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