Question

Looking at this question I started thinking about how to handle constructor requirements in C#.

Assume that I have:

T SomeMethod<T>(string s) : where T : MyInterface
{
    return new T(s);
}

I want to set the requirement on T that it can be constructed out of a string, but as far as I know, constructor definitions are not allowed as part of interfaces. Is there a standard way to solve this?

Answer 1

Add an init method or a property to your interface,

public interface MyInterface
{
    void Init(string s);
    string S { get; set; }
}

T SomeMethod<T>(string s) : where T : MyInterface, new()
{
    var t = new T();
    t.Init(s);

    var t = new T
    { 
        S = s
    };

    return t;
}

As you can’t specify arguments to constructor constraints