Programmatically create Logins and grant permission to SQL Server Database using C# .Net

To create Logins you need to connect to database using Admin account and then use the following query

CREATE LOGIN mudassar WITH PASSWORD = '12345' MUST_CHANGE

Now to use this Login you can pick connection string from Web.Config and just replace Username and Password with the one created.

meaning next time if you want use to change password forcefully. If not required remove it

And for permission queries refer

http://www.mssqltips.com/sqlservertip/1138/giving-and-removing-permissions-in-sql-server/