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List(T).FindAll Method

Retrieves all the elements that match the conditions defined by the specified predicate.

Namespace:  System.Collections.Generic
Assembly:  mscorlib (in mscorlib.dll)

member FindAll : 
        match:Predicate<'T> -> List<'T> 

Parameters

match
Type: System.Predicate(T)

The Predicate(T) delegate that defines the conditions of the elements to search for.

Return Value

Type: System.Collections.Generic.List(T)
A List(T) containing all the elements that match the conditions defined by the specified predicate, if found; otherwise, an empty List(T).

ExceptionCondition
ArgumentNullException

match is a null reference (Nothing in Visual Basic).

The Predicate(T) is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. The elements of the current List(T) are individually passed to the Predicate(T) delegate, and the elements that match the conditions are saved in the returned List(T).

This method performs a linear search; therefore, this method is an O(n) operation, where n is Count.

The following example demonstrates the find methods for the List(T) class. The example for the List(T) class contains book objects, of class Book, using the data from the Sample XML File: Books (LINQ to XML). The FillList method in the example uses LINQ to XML to parse the values from the XML to property values of the book objects.

The following table describes the examples provided for the find methods.

Method

Example

Find(Predicate(T))

Finds a book by an ID using the IDToFind predicate delegate.

C# example uses an anonymous delegate.

FindAll(Predicate(T))

Find all books that whose Genre property is "Computer" using the FindComputer predicate delegate.

FindLast(Predicate(T))

Finds the last book in the collection that has a publish date before 2001, using the PubBefore2001 predicate delegate.

C# example uses an anonymous delegate.

FindIndex(Predicate(T))

Finds the index of first computer book using the FindComputer predicate delegate.

FindLastIndex(Predicate(T))

Finds the index of the last computer book using the FindComputer predicate delegate.

FindIndex(Int32, Int32, Predicate(T))

Finds the index of first computer book in the second half of the collection, using the FindComputer predicate delegate.

FindLastIndex(Int32, Int32, Predicate(T))

Finds the index of last computer book in the second half of the collection, using the FindComputer predicate delegate.

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

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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