如何在switch语句中的case之间暂停？ C＃。执行下一个案例之前的3秒延迟

This is a sample of my code. I want to have a 3 second delay before executing the next case (display picturebox). But When I tried using timer/stopwatch, the 3 second delay will only be on the 1st case and case2 will execute the same time as case1 (with no delay).This is a sample of my code. I want to have a 3