Count Error from Oracle database

[mbewers1]

Hi there

I've written the following method which counts the number of times a specific attribute value appears in the database. It works fine in Oracle SQL Developer but returns a: 'ORA-01722:invalid number' error when running in ASP.NET, so it must be an ASP.NET / C# problem.

The NTID attribute is a VarChar2, but only 3 values are actually non-numeric. Would it make any difference if I changed the data type to NUMBER? Currently, I can't change the data type as there are already values in the table.

public int CheckRegistration(string userId)
        {
            using (OracleConnection oce = new OracleConnection(ConnectionString))
            {
                string user = string.Format("'{0}'", userId);
                oce.Open();
                OracleCommand command = oce.CreateCommand();
                command.CommandType = CommandType.Text;
 
                string querystring = string.Format(@"
                SELECT COUNT(*) FROM TBLADMINCODES
                WHERE NTID = {0}", user);
                command.Prepare();
            }
            return (int) command.ExecuteScalar();
        }

I can't change the data type anyway as there is already data in the table.
What can I do to eliminate this error?

Thanks Matt.