C switch nested syntax

You can put a switch As an external switch Part of a sequence of statements , That is, it can be in a switch Use another switch sentence ;

If internal and external switch Of case Constants contain common values , There's no contradiction ;

private void button1_Click(object sender, EventArgs e)
        {
            char ch1, ch2;
            ch1 = 'A';
            ch2 = 'A';

            switch (ch1)
            {
                case 'A':
                    MessageBox.Show(" It's external A！");
                    switch (ch2)
                    {
                        case 'A':
                            MessageBox.Show(" It's internal A!");
                            break;
                        case 'B': /*  Inside  B case  Code  */
                            break;
                    }
                    break;
                case 'B': /*  external  B case  Code  */
                    break;
            }
        }

Run the following ;