Whats a fast way to check that reference is a specific generic type?

Question

If I have a method with a parameter that's an interface, whats the fasts way to see if the interface's reference is of a specific generic type?

More specifically, if I have:

interface IVehicle{}

class Car<T> : IVehicle {}

CheckType(IVehicle param)
{
    // How do I check that param is Car<int>?
}

I'm also going to have to cast after the check. So if there is a way to kill 2 birds with one stone on this one let me know.

Answer 1

To check if param is a Car<int> you can use "is" and "as" as normal:

CheckType(IVehicle param)
{
    Car<int> car = param as Car<int>;
    if (car != null)
    {
         ...
    }
}

Answer 2

I often find that if my code requires me to write checks for specific types, I'm probably doing something wrong. You didn't give us enough context for us to give advice on this, though.

Does this meet your needs?

Car<int> carOfInt = param as Car<int>;
if (carOfInt != null)
{
    // .. yes, it's a Car<int>
}

Answer 3

Use the "as" operator to do it all in one shot. "as" will return either an object of the type you want, or null if what you're checking against doesn't match. This will only work for reference types, though.

interface IVehicle { }
class Car<T> : IVehicle 
{
    static Car<int> CheckType(IVehicle v)
    {
        return v as Car<int>;
    }
}

The "is" operator will let you test to see if v is an instance of Car<int>.

Answer 4

Or, you can just do:

if(param is Car<int>)
{
    // Hey, I'm a Car<int>!
}

Answer 5

Why not make this generic?

interface IVehicle{}

class Car<T> : IVehicle {

    public static bool CheckType(IVehicle param)
    {
        return param is Car<T>;
    }
}

...

Car<string> c1 = new Car<string>();
Car<int> c2 = new Car<int>();
Console.WriteLine(Car<int>.CheckType(c1));
Console.WriteLine(Car<int>.CheckType(c2));