Noob Issue with Activate.CreateInstance

Question

I am working on being able to dynamically invoke an instantiation of a class dynamically at run time.

I have spent the better part of this morning searching Google for an answer but I am pretty green in this world so I am sure the answers make sense, but they do not to me.

public class MSD : IGBRule
{
    public MSD(GoverningBodyRulesGet_Result GBRule, int UserID)
    {}

The line error and the error are both below

object v = Activator.CreateInstance(Type.GetType("RulesEngine.Rules.MSD, RulesEngine.Rules"), UserID, GBRules);

System.MissingMethodException: 'Constructor on type 'RulesEngine.Rules.MSD' not found.'

Answer 1

If you want to create an object and pass arguments to the constructor, you will have to provide the arguments in the correct order, matching the order you have specified in your constructor. So in your case, you want to pass the rule before the user id:

var type = Type.GetType("RulesEngine.Rules.MSD, RulesEngine.Rules");
object v = Activator.CreateInstance(type, GBRules, UserID);

If you pass the constructor arguments directly to the CreateInstance method, you will have to be careful with common types as it is possible that you are accidentally selecting a different overload that doesn't call the correct constructor. You can avoid that by passing an object array with the arguments you want to pass:

var type = Type.GetType("RulesEngine.Rules.MSD, RulesEngine.Rules");
object[] args = new object[] { GBRules, UserID };
object v = Activator.CreateInstance(type, args);