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Queryable.Where(TSource) Method (IQueryable(TSource), Expression(Func(TSource, Int32, Boolean)))

Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function.

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

static member Where : 
        source:IQueryable<'TSource> * 
        predicate:Expression<Func<'TSource, int, bool>> -> IQueryable<'TSource> 

Type Parameters


The type of the elements of source.


Type: System.Linq.IQueryable(TSource)
An IQueryable(T) to filter.
Type: System.Linq.Expressions.Expression(Func(TSource, Int32, Boolean))
A function to test each element for a condition; the second parameter of the function represents the index of the element in the source sequence.

Return Value

Type: System.Linq.IQueryable(TSource)
An IQueryable(T) that contains elements from the input sequence that satisfy the condition specified by predicate.

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. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).


source or predicate is a null reference (Nothing in Visual Basic).

This method has at least one parameter of type Expression(TDelegate) whose type argument is one of the Func(T, TResult) types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression(TDelegate).

The Where(TSource)(IQueryable(TSource), Expression(Func(TSource, Int32, Boolean))) method generates a MethodCallExpression that represents calling Where(TSource)(IQueryable(TSource), Expression(Func(TSource, Int32, Boolean))) itself as a constructed generic method. It then passes the MethodCallExpression to the CreateQuery(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 Where(TSource)(IQueryable(TSource), Expression(Func(TSource, Int32, Boolean))) depends on the implementation of the type of the source parameter. The expected behavior is that it returns the elements from source that satisfy the condition specified by predicate. The index of each source element is provided as the second argument to predicate.

The following code example demonstrates how to use Where(TSource)(IQueryable(TSource), Expression(Func(TSource, Int32, Boolean))) to filter a sequence based on a predicate that incorporates the index of each element.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.