方法约束必须是泛型类的超类

Question

How can I do the following?

I have a method which I need to say its generic type must be the super of the classes generic type.

Here is an example:

class Logger : ILogger, IStartable {}

///use
new FluentBuilder<Logger>().As<ILogger>().As<IStartable>();

This shows my intent, however does not work (as it is not syntactically incorrect):

public class FluentBuilder<TService> where TService : class
{
    public FluentBuilder<TService> As<TContract>() where TService : TContract
    {
        return this;
    }
}

Answer 1

This is not exactlywhat you want, but maybe a step in the correct direction. You can implement your As method as extension method:

public static class Ex
{
    public static FluentBuilder<TService> As<TService, TContract>(this FluentBuilder<TService> that) 
        where TContract : class 
        where TService : class, TContract
    {
        return that;
    }
}

The usage syntax is then:

new FluentBuilder<Logger>().As<Logger, ILogger>().As<Logger, IStartable>();