Question

I have a public class with 2 constructors: The default (without parameters), which is internal, and a different one, which is public.
The default constructor calls the other one with some default values.

I call the internal constructor using reflection, so it’s not used anywhere in the assembly statically (only by reflection).

When I make the reflection call, I’m getting:

System.MissingMethodException
    Message=No parameterless constructor defined for this object.

I know of two workarounds:

1. Make the constructor public (but I don’t want the users of this assembly to use it).
2. Call the constructor from some public method (I have many classes like this one, so I don’t want to write a lot of this ugly useless code).

Any better solutions to this problem?

It’s worth mentioning that if the default constructor is public, I don’t get that exception.

Thanks,

Boaz.

Answer 1

The constructor is not removed, probably in the search of your constructor you should specify the flag BindingFlag.NonPublic.

    class xxx
    {
        private xxx() :
            this(10)
        {
        }

        public xxx(int value)
        {
            Console.WriteLine(value);
        }
    }

    static void Main(string[] args)
    {
        Activator.CreateInstance(typeof(xxx), true);
        Console.ReadLine();
    }

Activator.CreateInstance have an overload with a boolean where you can specify if you want to call a non public constructor.

public static Object CreateInstance(
    Type type,
    bool nonPublic
)

Activator.CreateInstance(type, true) will call the constructor both if it is public or private\internal\protected.