What is the difference between Activator.CreateInstance and a standard constructor?

Question

What is the diffrenece between the two examples below? What is the purpose of Activator, why would I use it?

1.

string objTypeName = "Foo";
Foo foo = (Foo)Activator.CreateInstance(Type.GetType(objTypeName));

2.

Foo foo = new Foo()

I went through below the pages linked below, but didn't get a clear picture.

Here , here and here.

as an aside, if you take time to format your question nicely and make it as readable as you can, it is much more likely to be answered and upvoted. — Jodrell, Nov 07 '12 at 18:13

score 2 · Answer 1 · answered Nov 07 '12 at 17:58

With Activator.CreateInstance you can create objects even when cannot directly access the class it should belong to (e.g. Reflection), so you can for example create an object of the same type as another object:

var duplicate = Activator.CreateInstance(original.GetType());

This is not possible if you do not exactly know the class of your original object.

score 2 · Accepted Answer · answered Nov 07 '12 at 18:10

If you know the type that you will instantiate at design time then there is no need to use Activator.CreateInstance. All Activator.CreateInstance does is call the public default constructor.

Activator.CreateInstance is one form of "Late Binding" that can be useful if you want to instantiate a Type that you do not know at design time. If you already know the type of the concrete class at design time then you definitely want to instantiate it using "Early Binding", its much faster and simpler, and obvious. i.e. call the appropriate constructor directly.

score 1 · Answer 3 · answered Nov 07 '12 at 17:58

1

Activator.CreatInstance will call class Foo's default constructor.

The only difference is, if you know your type ahead of type, then creating it with new make a lot more sense (and readability)

answered Nov 07 '12 at 17:58

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What is the difference between Activator.CreateInstance and a standard constructor?

3 Answers3