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Enumerable.OfType<TResult> Method

Filters the elements of an IEnumerable based on a specified type.

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

public static IEnumerable<TResult> OfType<TResult>(
	this IEnumerable source

Type Parameters


The type to filter the elements of the sequence on.


Type: System.Collections.IEnumerable
The IEnumerable whose elements to filter.

Return Value

Type: System.Collections.Generic.IEnumerable<TResult>
An IEnumerable<T> that contains elements from the input sequence of type TResult.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable. 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 is null.

This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

The OfType<TResult>(IEnumerable) method returns only those elements in source that can be cast to type TResult. To instead receive an exception if an element cannot be cast to type TResult, use Cast<TResult>(IEnumerable).

This method is one of the few standard query operator methods that can be applied to a collection that has a non-parameterized type, such as an ArrayList. This is because OfType<TResult> extends the type IEnumerable. OfType<TResult> cannot only be applied to collections that are based on the parameterized IEnumerable<T> type, but collections that are based on the non-parameterized IEnumerable type also.

By applying OfType<TResult> to a collection that implements IEnumerable, you gain the ability to query the collection by using the standard query operators. For example, specifying a type argument of Object to OfType<TResult> would return an object of type IEnumerable<Object> in C# or IEnumerable(Of Object) in Visual Basic, to which the standard query operators can be applied.

The following code example demonstrates how to use OfType<TResult> to filter the elements of an IEnumerable.

            System.Collections.ArrayList fruits = new System.Collections.ArrayList(4);

            // Apply OfType() to the ArrayList.
            IEnumerable<string> query1 = fruits.OfType<string>();

            Console.WriteLine("Elements of type 'string' are:");
            foreach (string fruit in query1)

            // The following query shows that the standard query operators such as 
            // Where() can be applied to the ArrayList type after calling OfType().
            IEnumerable<string> query2 =
                fruits.OfType<string>().Where(fruit => fruit.ToLower().Contains("n"));

            Console.WriteLine("\nThe following strings contain 'n':");
            foreach (string fruit in query2)

            // This code produces the following output:
            // Elements of type 'string' are:
            // Mango
            // Orange
            // Apple
            // Banana
            // The following strings contain 'n':
            // Mango
            // Orange
            // Banana

.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.