Standalone C# Windows Application with SQLCe 3.5 Database

Question

Hi,
i wanted to create a standalone c# windows application with SQLCe 3.5 databse for my client
i have done with adding .sdf file and the coding part for connecting to .sdf file and i have created a code to check login credential from the .sdf file it is working properly but when i try to update password its showing me success message that password has been updated but when i check the database no changes were made to it.....

you can download my source code from here:
https://skydrive.live.com/redir?resid=E2A87E111B4C7762!121&authkey=!AMYz7WSzR9Q64Yk


its my first application with the above requirement please help me........
Sir Mahesh Chand Please Help me.....

Regards Sufiyan