public void TestDemo2Itf()
 {
     ICalc calc = new Calculator();
     Assert.AreEqual(30, calc.Add(10, 20));
 }
 public void TestDemo2Dynamic()
 {
     dynamic calc = new Calculator();
     Assert.AreEqual(30, calc.Add(10, 20));
 }
 public void TestDemo2Static()
 {
     Calculator calc = new Calculator();
     Assert.AreEqual(30, calc.Add(10, 20));
 }