Activator.CreateInstance<T> Vs new

Question

Is there any difference between following two ways of creating an object.

Student s1 = Activator.CreateInstance<Student>(); Student s1 = new Student(); 

• Is there any difference in the way constructor is called or in initializing the memory?
• Per my understanding, the first method looks completely redundant. If the programmer knows data type during design time, he will use the second method.

Answer 1

This overload of the "Activator.CreateInstance" method is used by compilers to implement the instantiation of types specified by type parameters using generics.

Say you have the following method:

public static T Factory<T>() where T: new() {     return new T(); } 

The compiler will convert the "return new T();" to call "CreateInstance".

In general, there is no use for the CreateInstance in application code, because the type must be known at compile time. If the type is known at compile time, normal instantiation syntax can be used (new operator in C#, New in Visual Basic, gcnew in C++).

More Info: http://msdn.microsoft.com/en-us/library/0hcyx2kd.aspx

Answer 2

I wouldn't call Activator.CreateInstance() redundant.

If you know the type, yes, you'd just use new. However, in situations requiring dynamic loading of unknown types from plugin frameworks or where the type is parsed from a string (from, say, a settings-file), it's extremely useful.

And to answer the question as to the difference between the two, no, under the hood there is no real difference between calling new T() and Activator.CreateInstance<T>(), as has already been pointed out by Andrew Hare.

EDIT: Never mind, I've confused the generic CreateInstance<T>() with the otherwise more normally used CreateInstance(Type type)