Question

I have created two custom controls. On the basis of features any one of them will be selected and used in C# application. I have loaded the desired control but how i can use there functions e.g There is a public function of my control LoadXML() . Both controls contain this function.
Only one control will be loaded at one time.

Answer 1

Create an instance of your control, then add it to the form, after that you can call its public exposed methods.

 TestControl myTestControl = new TestControl();
 this.Controls.Add(myTestControl);
 myTestControl.LoadXML();

If you are loading controls through dll, try this to call the method:

    // Use the file name to load the assembly into the current
    // application domain.
    Assembly a = Assembly.Load("example");
    // Get the type to use.
    Type myType = a.GetType("Example");
    // Get the method to call.
    MethodInfo myMethod = myType.GetMethod("MethodA");
    // Create an instance.
    object obj = Activator.CreateInstance(myType);
    // Execute the method.
    myMethod.Invoke(obj, null);

http://msdn.microsoft.com/en-us/library/25y1ya39.aspx