Queryable.Cast<TResult>(IQueryable) Method

Definition

Namespace:

System.Linq

Assemblies:

netstandard.dll, System.Linq.Queryable.dll

Source:

Queryable.cs

Converts the elements of an IQueryable to the specified type.

C#

public static System.Linq.IQueryable<TResult> Cast<TResult>(this System.Linq.IQueryable source);

Type Parameters

TResult

The type to convert the elements of source to.

Parameters

source

IQueryable

The IQueryable that contains the elements to be converted.

Returns

IQueryable<TResult>

An IQueryable<T> that contains each element of the source sequence converted to the specified type.

Exceptions

ArgumentNullException

source is null.

InvalidCastException

An element in the sequence cannot be cast to type TResult.

Examples

The following code example demonstrates how to use Cast<TResult>(IQueryable) to convert objects in a sequence to type String.

C#

// 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
*/

Remarks

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.

Applies to