Initialize an object from string type

Question

Hello!

I have list of strings with class types on this format:

"MyProject.Classes.MyClass"

How can I instantiate objects of these classes on runtime. Do I have to use reflection? I'm not familiar with that so unsure of the usage.

 

So I would like something like this

var MyObject = new TheCorrectClassBasedOnTheString();

 

Best regards

Ola

Answer 1

Hi,

yes, you need a little bit of reflection.

First you get the Type itself. For that, you can use Type.GetType(String) or Type.GetType(String, Boolean) function.

The next step is, to get the constructor: yourType.GetConstructor(...). That will give you a ConstructorInfo object and you can call the Method Invoke on it.

Please see the msdn documentation of the given classes / methods to find more details and examples.

With kind regards,

Konrad

Answer 2

Hello Konrad, Thanks for the quick answer!

I am able to get the Type, but not the contstructor. Can you check this code, and see if I missed something?

Type oType = Type.GetType(objectTypeString);
var constructor = oType.GetConstructor(new Type[] { oType }); // constructor is null after this line
var s = j.Invoke(null); // what parameter should i use here?

I just want to get the default constructor.

I will check the MSDN documentation on this also.

Thank you

Ola

Answer 3

You do not need to get the constructor. Just use Activator.CreateInstance Method and pass the type you have.

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MCTS, CodeProject MVP 2008

Answer 4

I found another way to initiate the object when I have gotten the type.

 

Type oType = Type.GetType(objectTypeString);
var myObject = Activator.CreateInstance(oType);

 

This worked for me. Thanks for leading me in the right direction Konrad!

Ola

Answer 5

Ahh great. I always used the other way I described. In the code, you tried is a simple error:
GetConstructor gets the types that are the arguments for the Constructor. So instead of
var constructor = oType.GetConstructor(new Type[] { oType });
you should try:
var constructor = oType.GetConstructor(new Type[] { });

But the Activator Class is very interesting. Thank you Giorgi to point to this possibility!

With kind regards,

Konrad