How to Get T argument in generic class and return another type in Interface

I want to use this code:

List<U> SelectAll<T>() where T : class;

the problem is I want to pass T type and get U type but c# has T keyword but does not have U keyword.how I can Pass T type ad get another Type in Interface declration>

thanks

Sorry I post Answer here but I want show you code: I'm writing this code:

interface IRepoitory<T> where T : class
{
    T CreateInstance();

    IEnumerable<U> SelectAll();

what can I write instead of "U"? when I Impelement interface and I have this code:

IEnumerable<TResult> SelectAll<TResult>();

In Class that implement the interface I cant Return Any class instead of TResult thanks

T is not a keyword in C# - it's just a conventional name for a type parameter. If you want to specify multiple type parameters, you can do so very easily:

public static List<U> SelectAll<T, U>() where T : class

(It's not clear where the data's coming from or how T will be used here, admittedly.)

Conventionally type parameters either are T or start with T, so you might want:

public static List<TResult> SelectAll<TResult>() where T : class

If you can clarify what you're trying to do, we may be able to help more.

    public static List<TResult> SelectAll<T, TResult>(T inParam) where T: class
    {
        return new List<TResult>();
    }

Is that you want?? If you don't know the type of result, you need to tell method compiler what type to return. This is done using SelectAll<T, TResult>