asp.net mvc - ViewData to get data from SQL database does not work -

i trying data database gives me null data. due unable use viewdata in aspx file. missing ?

  studentdata data = new studentdata();              using (var connection = databaseconnectivity.getbranchconnection())             using (var command = connection.createcommand())             {                 command.commandtext = databaseconnectivity.getisolationlevelstatement(system.data.isolationlevel.readcommitted) +                     @"select" +                         @"branch_name [branchname]," +                         @"customerid [customerid]," +                         @"firstname [firstname]," +                         @"lastname [lastname]," +                         @"grades [grades]" +                     @"from branchdata";                  connection.open();                     viewdata["branchname"] = data.branchname;                     viewdata["customerid"] = data.customerid;                     viewdata["firstname"] = data.firstname;                     viewdata["lastname"] = data.lastname;                     viewdata["grades"] = data.grades; }             return view("studentdetails", data);