Question

Is there any way to do code such this:

class GenericClass<T>
{
    void functionA()
    {
        T.A();
    }
}

Or, how to call a function of type parameter (type is some my custom class).

Answer 1

To call a method of a generic type object you have to instantiate it first.

public static void RunSnippet()
{
    var c = new GenericClass<SomeType>();
}

public class GenericClass<T> where T : SomeType, new()
{
    public GenericClass(){
        (new T()).functionA();
    }   
}

public class SomeType
{
    public void functionA()
    {
        //do something here
        Console.WriteLine("I wrote this");
    }
}