public void AlreadySetDoubleChangeEventArgs(double?oldValue, double?newValue1, double?newValue2)
        {
            ChangeEventArgs <double?> changeEventArgs1 = new ChangeEventArgs <double?>(oldValue);
            ChangeEventArgs <double?> changeEventArgs2 = new ChangeEventArgs <double?>(oldValue, newValue1);

            try
            {
                changeEventArgs1.SetNewValue(newValue2);
                Assert.Equal(newValue2, changeEventArgs1.NewValue);
                changeEventArgs2.SetNewValue(newValue2);
            }
            catch (Exception ex)
            {
                Assert.IsType <AlreadySetException <double?> >(ex);
            }
        }