exception in executing a stored procedure

  try {

                string conStr = WebConfigurationManager.ConnectionStrings[0].ConnectionString;
                SqlDataAdapter adapter;
                DataTable ans = new DataTable();
                SqlConnection connection = new SqlConnection(conStr);
                SqlCommand command = new SqlCommand();
                command.CommandType = CommandType.StoredProcedure;
                command.CommandText = "usp_GetUserDetails";
 
                command.Parameters.Add("@UserName", SqlDbType.VarChar);
                command.Parameters.Add("@Password", SqlDbType.VarChar);
                command.Parameters["@UserName"].Value = user;
                command.Parameters["@UserName"].Direction = ParameterDirection.Input;
                command.Parameters["@Password"].Value = pass;
                command.Parameters["@Password"].Direction = ParameterDirection.Input;
 
                adapter = new SqlDataAdapter(command.CommandText, connection);
                adapter.Fill(ans);
 
                return ans; 
            }
            catch (Exception ex)
            {
                throw ex;
            }

 name="MainConnectionString" connectionString="Data Source=MIKLAT\SQLEXPRESS;Initial Catalog=...;Integrated Security=True; providerName="System.Data.SqlClient"/>