Queryable.OfType<TResult> Method
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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)
Syntax
'Declaration
<ExtensionAttribute> _
Public Shared Function OfType(Of TResult) ( _
source As IQueryable _
) As IQueryable(Of TResult)
public static IQueryable<TResult> OfType<TResult>(
this IQueryable source
)
Type Parameters
- TResult
The type to filter the elements of the sequence on.
Parameters
- source
Type: System.Linq.IQueryable
An IQueryable whose elements to filter.
Return Value
Type: System.Linq.IQueryable<TResult>
A collection that contains the elements from source that have type TResult.
Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type IQueryable. When you use instance method syntax to call this method, omit the first parameter.
Exceptions
| Exception | Condition |
|---|---|
| ArgumentNullException | source is nulla null reference (Nothing in Visual Basic). |
Remarks
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.
Examples
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.
outputBlock.Text &= output.ToString() & vbCrLf
' This code produces the following output:
' Members of type 'PropertyInfo' are:
' Chars
' Length
// Create a list of MemberInfo objects.
List<System.Reflection.MemberInfo> members = typeof(String).GetMembers().ToList();
// Return only those items that can be cast to type PropertyInfo.
IQueryable<System.Reflection.PropertyInfo> propertiesOnly =
members.AsQueryable().OfType<System.Reflection.PropertyInfo>();
outputBlock.Text += "Members of type 'PropertyInfo' are:" + "\n";
foreach (System.Reflection.PropertyInfo pi in propertiesOnly)
outputBlock.Text += pi.Name + "\n";
/*
This code produces the following output:
Members of type 'PropertyInfo' are:
Chars
Length
*/
Version Information
Silverlight
Supported in: 5, 4, 3
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.