Show loading splash while executing command in ASP.Net

Hello,

Can someone tell me how i can make to show loading splash window while executing some commands?

Example let's say i have login form that connects to mysql and i want while the program try to connect and get the data to display splash screen with some information like "please wait" until it gets the results then to close it before show results.

Also this to be used by other call methods like update, delete and other stuff so i can call this method everywhere to display it until it shows/loads the information.