I'm trying to make a super simple program where you use 10 different buttons to write in a code (kind of like the code to the door of an appartment complex). All the buttons have this click event:

```
    private void number_click(object sender, EventArgs e)
    {
        var button = (sender as Button);

        if (code.Length == 4)
        {
            code.Remove(0, 1);
        }

        switch (button.Name)
        {
            case "button_1":
                code += "1";
                break;

            case "button_2":
                code += "2";
                break;

            case "button_3":
                code += "3";
                break;

            case "button_4":
                code += "4";
                break;

            case "button_5":
                code += "5";
                break;

            case "button_6":
                code += "6";
                break;

            case "button_7":
                code += "7";
                break;

            case "button_8":
                code += "8";
                break;

            case "button_9":
                code += "9";
                break;

            case "button_0":
                code += "0";
                break;
        }

        label1.Text = code;
    }

```

I'm simply trying to make so the number the user presses get added to the code string. When there length of the string reaches 4 it is supposed to remove the first character so that there is never more than 4 characters in the string. For some reason this doesn't seem to work. What am I doing wrong?