c# - Error while trying populate DropDownListFor from Database -

i trying populate dropdownlistfor items database, when tried run program, gives me error object reference not set instance. method (get data database , put selectlist) did not called @ all, though have called , set controller.

could please tell me going wrong?

here code using:

get data database: (inventory class) (row id table below there default when created database)

private string connectionstring = @"data source=(localdb)\v11.0;attachdbfilename=|datadirectory|\db1.mdf;integrated security=true";  [display(name = "moduledata:")] public string moduledata     {         get;         set;     }  public string id     {         get;         set;     }  public string name     {         get;         set;     }  public ienumerable<selectlistitem> listdata     {         get;         set;     }  public selectlist getdata()         {             list<selectlistitem> lists = new list<selectlistitem>();              using (sqlconnection conn = new sqlconnection(connectionstring))             {                 string query = "select [id], [name] [query]";                  conn.open();                  using (sqlcommand cmd = new sqlcommand(query, conn))                 {                     using (sqldatareader reader = cmd.executereader())                     {                         while (reader.read())                         {                             id = reader["id"].tostring();                              name = reader["name"].tostring();                              lists.add(new selectlistitem() { text = name, value = id });                         }                     }                 }                  conn.close();             }              return new selectlist(lists, "value", "text");         } 

controller:

inventory repository = new inventory();  [httpget] public actionresult module()         {             repository.listdata = repository.getdata();              return view();         }  [httppost] public actionresult module(inventory inven)         {             // there button later on , here want value of selected `dropdownlistfor`             return view(inven);         } 

view (module):

@model project_name.inventory @{     viewbag.title = "inventory"; }  <h2>inventory</h2> <br />  @using (html.beginform()) {     <div>         <fieldset>             <legend>inventory</legend>             <div class="editor-label">                 @html.labelfor(u => u.moduledata)             </div>             <div class="editor-field">                 @html.dropdownlistfor(u => u.id, model.listdata)             </div>         </fieldset>     </div> } 

above code using, once ran program, gives me error on @html.dropdownlistfor(u => u.id, model.listdata) says object reference not set instance of object.

that of question.

thank much

your answer appreciated.

in method, assign selectlist used @html.dropdownlist() using

repository.listdata = repository.getdata(); 

however in when post , return view, not reassign selectlist, hence model.listdata null. need repeat above line of code before call return view(inven);

you need return model in method

repository.listdata = repository.getdata(); return view(repository); // change