public void MyMethod()
{
Table1 t1 = new Table1();
Table1 t2 = new Table2();
Table1 t3 = new Table3();
t1.UsingMethod2(); // will be called from ITableBaseExtensions
t1.Method2(); // will be called from ITableBase - must implemented in Table1 class
t2.Method3(some_argument); // will be called from ITableBase - must implemented in Table2 class
t2.GetIdAsString(); // will be called from ITableBaseExtensions
// etc.
}