CODEWITHSUNDEEP
c#.netreflection
user1311199
user1311199

Reputation: 119

Creating an object with a string

So, here's the deal. I have an interface called IBehavior. Each one of my Entity's has a variable: private IBehavior _behavior. Each Entity also has a variable: public string Behavior. Upon loading my entitys the string is filled from an xml file. Subsequently a function called init() is called on all entitys. This method takes the string and uses this line of code to call the desired constructor: Type.GetType(Behavior).GetConstructor(Type.EmptyTypes).Invoke(null);.

Unfortunately, the Invoke() method returns something of type Object, and the _behavior variable wont accept this without a cast. I have tried this approach: _behavior = (IBehavior)Type.GetType(Behavior).GetConstructor(Type.EmptyTypes).Invoke(null);.

All this did was tell me that my _bahavior variable was null and therefore this could not happen. I'm probably using GetConstructor() incorrectly. Can someone please point me in the right direction?

Init Function: 

public void Init()
{
  if (Behavior == "null" || Behavior == "none")
  {
    _behavior = null;
    return;
  }

  _behavior = (IBehavior) Type.GetType(Behavior).GetConstructor(Type.EmptyTypes).Invoke(new object(), null);
}

Upvotes: 1

Views: 196

Answers (1)

Konrad Kokosa
Konrad Kokosa

Reputation: 16878

To create type from its name use:

_behavior = (IBehavior)Activator.CreateInstance(Type.GetType(Behavior));

The other problem with your code is that you are calling constructor on new object() because you use MethodBase.Invoke(Object, Object[]) method: 

.GetConstructor(Type.EmptyTypes).Invoke(new object(), null)

and by specifying only array of object, you use ConstructorInfo.Invoke(Object[]) method:

_behavior = (IBehavior)Type.GetType(Behavior)
                           .GetConstructor(Type.EmptyTypes)
                           .Invoke(new object[] { });

Note: If you receive ArgumentNullException from Activator.CreateInstance, remember that type must be specified with namespace (if defined in the same assembly), like:

Activator.CreateInstance(Type.GetType("ConsoleApplication.SomeClass"))

Upvotes: 3

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