Queryable.OfType(Of TResult) Method (IQueryable)

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

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

<ExtensionAttribute>
Public Shared Function OfType(Of TResult) (
	source As IQueryable
) As IQueryable(Of TResult)

Parameters

source
Type: System.Linq.IQueryable

An IQueryable whose elements to filter.

Return Value

Type: System.Linq.IQueryable(Of TResult)

A collection that contains the elements from source that have type TResult.

Type Parameters

TResult

The type to filter the elements of the sequence on.

Exception Condition
ArgumentNullException

source is null.

The OfType method generates a MethodCallExpression that represents calling OfType 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 OfType depends on the implementation of the type of the source parameter. The expected behavior is that it filters out any elements in source that are not of type TResult.

The following code example demonstrates how to use OfType to filter out elements that are not of type PropertyInfo from a list of elements of type MemberInfo.

' Create a list of MemberInfo objects.
Dim members As List(Of System.Reflection.MemberInfo) = GetType(String).GetMembers().ToList()

' Return only those items that can be cast to type PropertyInfo.
Dim propertiesOnly As IQueryable(Of System.Reflection.PropertyInfo) = _
        members.AsQueryable().OfType(Of System.Reflection.PropertyInfo)()

Dim output As New System.Text.StringBuilder
output.AppendLine("Members of type 'PropertyInfo' are:")
For Each pi As System.Reflection.PropertyInfo In propertiesOnly
    output.AppendLine(pi.Name)
Next

' Display the output.
MsgBox(output.ToString())

' This code produces the following output:

' Members of type 'PropertyInfo' are:
' Chars
' Length

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.1
Windows Phone
Available since 8.1
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