Question

Is there a way to Define a default constructor for all classes in a given assembly. For example I have classes like this in an assembly –

public class SomeClass
{
    public SomeClass(int x, int y)
    {
    }
}

These classes all require a default constructor but I don’t want to have to riddle all of these classes with a default constructor so how do I do this using reflection or something similar?? (Perhaps TypeBuilder.DefineDefaultConstructor?)

Answer 1

These classes all require a default constructor but I don’t want to have to riddle all of these classes with a default constructor

If the classes require a constructor, you should include it. Anything else will be a nightmare in terms of maintenance.

The main issue with auto-generating a constructor is that the default constructor needs to know about the class in question, because it needs to properly initialize the values of the class. In your example, your default constructor would need to do something to set the internal state normally created with x and y. There is no way to know what that something should be without knowledge of the class, so the class is where it should be defined.

That being said, there isn’t a direct way to just “add constructors to every type”. You could, potentially, use a tool like Cecil to rewrite the assembly with your modifications – basically, load the assembly, inspect each type, add the new information, and rewrite it. Alternatively, you could use some form of AOP tool, like PostSharp, to create constructors at compile time based on some attributes or similar.

I would recommend against these approaches, however. I think that modifying the code itself and including the constructors when appropriate is the right approach.