Queryable.Cast<TResult> Method
Converts the elements of an IQueryable to the specified type.
Namespace: System.Linq
Assembly: System.Core (in System.Core.dll)
Type Parameters
- TResult
The type to convert the elements of source to.
Parameters
- source
- Type: System.Linq.IQueryable
The IQueryable that contains the elements to be converted.
Return Value
Type: System.Linq.IQueryable<TResult>An IQueryable<T> that contains each element of the source sequence converted to the specified type.
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. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).| Exception | Condition |
|---|---|
| ArgumentNullException | source is null. |
| InvalidCastException | An element in the sequence cannot be cast to type TResult. |
The Cast<TResult>(IQueryable) method generates a MethodCallExpression that represents calling Cast<TResult>(IQueryable) 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 Cast<TResult>(IQueryable) depends on the implementation of the type of the source parameter. The expected behavior is that it converts the values in source to type TResult.
The following code example demonstrates how to use Cast<TResult>(IQueryable) to convert objects in a sequence to type String.
// Create a list of objects.
List<object> words =
new List<object> { "green", "blue", "violet" };
// Cast the objects in the list to type 'string'
// and project the first letter of each string.
IEnumerable<string> query =
words.AsQueryable()
.Cast<string>()
.Select(str => str.Substring(0, 1));
foreach (string s in query)
Console.WriteLine(s);
/* This code produces the following output:
g
b
v
*/
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.
