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Queryable.TakeWhile(TSource) Method (IQueryable(TSource), Expression(Func(TSource, Boolean)))

Returns elements from a sequence as long as a specified condition is true.

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

JScript does not support generic types or methods.

Type Parameters


The type of the elements of source.


Type: System.Linq.IQueryable(TSource)

The sequence to return elements from.

Type: System.Linq.Expressions.Expression(Func(TSource, Boolean))

A function to test each element for a condition.

Return Value

Type: System.Linq.IQueryable(TSource)
An IQueryable(T) that contains elements from the input sequence occurring before the element at which the test specified by predicate no longer passes.

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 TakeWhile(TSource)(IQueryable(TSource), Expression(Func(TSource, Boolean))) method generates a MethodCallExpression that represents calling TakeWhile(TSource)(IQueryable(TSource), Expression(Func(TSource, 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 TakeWhile(TSource)(IQueryable(TSource), Expression(Func(TSource, Boolean))) depends on the implementation of the type of the source parameter. The expected behavior is that it applies predicate to each element in source until it finds an element for which predicate returns false. It returns all the elements up until that point.

The following code example demonstrates how to use TakeWhile(TSource)(IQueryable(TSource), Expression(Func(TSource, Boolean))) to return elements from the start of a sequence as long as a condition is true.

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

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

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

.NET Framework

Supported in: 3.5