Creating an object based on a type parameter

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I am having a problem bending my mind to situation. I have a class A with a method CreateInternals(). One of CreateInternals() tasks is to create a new B-object. There are several classes of B-object (B1, B2, B3...) but they all implement the interface IBable. The type of B object to be created is supposed to be passed to A.CreateInternals().
Now I know that I could just have CreateInternals accept a System.Type parameter

public void CreateInternals(System.Type BToMake)
{
	ConstructorInfo cInfo = type.GetConstructor(argTypes);
	IBable internalB = (IBable)cInfo.Invoke(new object[]());
	...
}

and call it with the appropriate type

A.CreateInternals(typeof(B2));

However, this would not prevent me from calling CreateInternals with an invalid type

A.CreateInternals(typeof(C));

and I would not see the error until runtime.

Is there a way to get the compiler to restrict CreateInternals to only accept BToMake parameters that implement IBable? Something like

public voide CreateInternals(System.Type BToMake where BToMake is IBable) {...}

I have the strange feeling that I can do this using generics, but I think I've been staring at the problem for so long that I have brain-lock and the answer just won't come.

Any help would be appreciated.

Posted 22-Apr-11 12:27pm

Clive D. Pottinger

Updated 22-Apr-11 12:43pm

v3

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Clive D. Pottinger 22-Apr-11 19:31pm

Thank you, orsobrown. I knew it was something fairly straight-forward, but like I said: brain-lock!

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Bruno Tagliapietra · Accepted Answer · 2011-04-22T12:56:00

2 ways of doing it. If you prefer NOT having to deal with instances of your object as parameters:

XML

public void CreateInternals<T>() where T:IBable
{
    Type theTypeIs = typeof(T);
..
..
..
}

CreateInternals<yourclassname>();
</yourclassname>

Otherwise, if you prefer passing instances as parameters:

XML

public static void CreateInternals<T>(T BToMake ) where T:IBable
{
    Type theTypeIs = BToMake.GetType();
..
..
..
}

CreateInternals(someInstanceImplementingYourInterfaceIBable);