如何从泛型类型调用重载方法

Question

I have defined a generic interface

interface IHandler<in TCommand> where TCommand:Command
{
     void Handle(TCommand command);
} 

And the class

public class MyHandler:
    IHandler<CommandA>,
    IHandler<CommandB>,
    IHandler<CommandC>
{
    public void Handle(CommandA command)
    {...}

    public void Handle(CommandB command)
    {...}

    public void Handle(CommandC command)
    {...}
}

For some reasons, I need to call the handler dynamically, and the things I have is the IoC container, a handler's qualified name and the parameter instance (eg CommandB). And my question is how can I invoke the Handle method?

public void DynamicCallHandleMethod(string typeName, Command command)
{
     Container container = new Container();
     container.Register<MyHandler>();

     object handler = container.Resolve(Type.GetType(typeName));
     //handler.Handle(command);  <---- How to make it?
}

Note, I know Reflection may be one of the solutions, so I hope there's another more elegant way, Thanks in advance.

Answer 1

Implement a Method handling a Command value that calls the respective (they might even be private then) methods:

public void Handle(Command command)
{
    if(command is CommandA comA)
        Handle(comA);
    else if(command is CommandB comB)
        Handle(comB);
    else if(command is CommandC comC)
        Handle(comC);
    else
        // Handle if necessary.
}

also casting the handler as an object on resolve will not expose the Interface. Either you need var or implicilty IHandler as type.

Answer 2

Create a 'dynamic' variable and assign it with 'command', then pass this to the handle method. This should resolve the type at runtime and select the appropriate method.

dynamic cmd = command;
handler.Handle( cmd );

Alternatively, look into implementing the visitor pattern.