AddwithValue isn't written like that:
cmd.Parameters.AddWithValue("@UserName", SqlDbType.NVarChar).Value =_UserName;
It shoudl be:
cmd.Parameters.AddWithValue("@UserName", _UserName);
Fix that, it should work.And fix this as well:
cmd.ParametersAddWithValue("@pwd", TestPassword);
But don't do passwords like that! Never store passwords in clear text - it is a major security risk. There is some information on how to do it here:
Password Storage: How to do it.[
^] - it'#s probably a bit advanced for you, but just use the code, and don't worry about how it works for the moment.