.NET Core Cast to interface with generic type parameter of type which implements interface

Question

In .NET Core C# I' trying something like this:

(IInterface<IParameter>)instance

Where instance is new Implementation<Parameter>()

And Implementation : IInterface & Parameter : IParameter

The issue is with the casting of the generic parameter. When I provide Parameter instead of IParameter it works but at compile time there is no way to know which type that implements IParameter will be used. All of these objects will be created via reflection.

So is there any way this cast works? Or some other way to implement this like providing no generic type parameter like you can with typeof.

EDIT Thanks to Ziriax

A Fully Working Example:

interface IInterface
{
    void Run(TInput input);
}

abstract class AbstractClass<TInput> : IInterface
    where TInput : IParameter
{
    public abstract void Execute(TInput input);

    public void Run(IParameter input)
    {
        Execute((TInput)input);
    }
}

interface IParameter {}

class Implementation : AbstractClass<Parameter>
{
    public void Run(Parameter input)
    {
    }
}

class Parameter : IParameter {}

class Program
{
    static void Main()
    {
        object instance = new Implementation();
        var castInstance = (IInterface) instance;
        castInstance.Run(new Parameter());
    }
}

Answer 1

Why don't you add a non-generic interface too:

interface IInterface
{
    void Run(IParameter input);
}

And then let your generic interface extend this non-generic one.

Obviously your implementations should cast the IParameter, someone needs to cast it... You could make an abstract base class that does this for you, so not every implementation has to do this.

You might also be interested in the double dispatch pattern, although I'm not sure this will work in your case.