Enumerable.Cast(Of TResult) Method
Assembly: System.Core (in System.Core.dll)
'Declaration <ExtensionAttribute> _ Public Shared Function Cast(Of TResult) ( _ source As IEnumerable _ ) As IEnumerable(Of TResult)
The type to convert the elements of source to.
Return ValueType: System.Collections.Generic.IEnumerable(Of )
An IEnumerable(Of T) that contains each element of the source sequence converted to the specified type.
Usage NoteIn 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.
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 method enables the standard query operators to be invoked on non-generic collections by supplying the necessary type information. For example, System.Collections.ArrayList does not implement IEnumerable(Of T), but by calling on the System.Collections.ArrayList object, the standard query operators can then be used to query the sequence.
If an element cannot be cast to type TResult, this method will throw an exception. To obtain only those elements that can be cast to type TResult, use the OfType(Of TResult) method instead of .
In a query expression, an explicitly typed iteration variable translates to an invocation of . This example shows the syntax for an explicitly typed range variable.
The following code example demonstrates how to use to enable the use of the standard query operators on an System.Collections.ArrayList.
' Create an ArrayList and add items to it. Dim fruits As New List(Of String)() fruits.Add("apple") fruits.Add("mango") ' Call Cast(Of String) to cast the ArrayList elements to strings. ' Then call Select() to project the strings as the query result. Dim query As IEnumerable(Of String) = _ fruits.Cast(Of String)().Select(Function(fruit) fruit) Dim output As New System.Text.StringBuilder For Each fruit As String In query output.AppendLine(fruit) Next ' Display the output. outputBlock.Text &= output.ToString() & vbCrLf ' This code produces the following output: ' ' apple ' mango