Generics in C#

I am coming accross a very interesting problem.
I have the following classes defined as follows:
public class classA
{
        public int Type {get;set;}

        public MyCollection<T> MyCol {get;set;}

        //other properties and methods
}

public class TypeA
{
//class definition
}

public class TypeB
{
//class definition
}

public class TypeC
{
//class definition
}

the problem is that I want MyCollection<T> to hold either TypeA, TypeB or TypeC depending on the value in classA.Type when instantiating classA.

I found a way to build a generic collection that can hold any of the three class but the problem is tyhat when I am defining MyCol property for classA I have to pick a specific class (classA, classB or classC)

Any idea??