使用C＃中的泛型进行转换

Question

Given the following snippet, how can I cast IMessage to type of TMessage ?

public void Publish<TMessage>(IMessage message) 
{
     var t = typeof(TMessage);
     MyFunction((t)message); // how can a cast message to type of TMessage?
}

Answer 1

Like any other cast:

public void Publish<TMessage>(IMessage message) {
    var t = (TMessage)message;
    MyFunction(t);
}

Edit: If compiler says 'invalid cast', then is probably right. However, for cases when compiler is not right, you can "trick" him.

public void Publish<TMessage>(IMessage message) {
    var t = (TMessage)(object)message;
    MyFunction(t);
}

Answer 2

public void Publish<TMessage>(IMessage message) {
    var t = message as TMessage;
    MyFunction(t);
}

It will set t as null instead of giving runtime error.

Answer 3

You no need to cast some parameters, just use generic methods.

// Your code
public void Publish<TMessage>(IMessage message) 
{
     var t = typeof(TMessage);
     MyFunction((t)message); // how can a cast message to type of TMessage?
}

// Modified version
public void Publish<TMessage>(TMessage message) where TMessage : IMessage
{
     MyFunction(message);
}