How to check/verify SQL login Credential

Hi,

I am making a module to backup SQL Db from webpage. I impersonate asp.net user to a given Windows Account and need to verify that account has required permission in SQL Server.

I don't know how to verify the windows account credential for SQL Server login.

Now what I am doing is to run SQL query against database to select row from some table, if it is successful, the user is valid SQL login. But I know it's not the way.

Any idea?

Thanks,

Why don't you just try to login and do the backup and if it fails you know you don't have permission