c# - Dynamically Generated Dropdowns Postback -

i'm having trouble same dynamically generated dropdowns , viewstate.

long story short, user upload excel file, file parsed , dropdowns created appropriate data. done on when asp button pressed, , controls added table follows:

public void generatefromsheet(ordereddictionary columns, datatable oppcolumns, list<string> requireddrops)     {         int index = 0;         foreach (dictionaryentry entry in columns)         {             dropdownlist ddl = new dropdownlist()             {                 id = "ddlmapping" + entry.key.tostring(),                 datasource = columns,                 datatextfield = "key",                 datavaluefield = "value",                 selectedindex = index,                 enabled = requireddrops.contains(entry.key) ? false : true             };              ddl.databind();              dropdownlist ddl2 = new dropdownlist()             {                 id = "opportunitymappingddl" + index,                 datasource = oppcolumns,                 datatextfield = "attributedisplayname",                 datavaluefield = "tablecolumnname"             };             ddl2.databind();               htmltablecell td = new htmltablecell()             {                 id = "tdmapping" + index             };             td.controls.add(ddl);              htmltablecell td2 = new htmltablecell()             {                 id = "tdoppmapping" + index             };             td2.controls.add(ddl2);              htmltablerow tr = new htmltablerow()             {                 id = "trmapping" + index             };             tr.cells.add(td);             tr.cells.add(td2);              tblfilemapping.rows.add(tr);             index++;         }     } 

however, on each postback after this, drop-downs erased. i've looked online solution , points recreating controls using same id's when created state can restored viewstate. i've tried follows below storing should create in viewstate:

public void generatefromviewstate()     {         ordereddictionary columns = (ordereddictionary) viewstate["xlcolumns"];          int index = 0;         foreach (dictionaryentry entry in columns)         {             dropdownlist ddl = new dropdownlist()             {                 id = "ddlmapping" + entry.key.tostring(),             };              dropdownlist ddl2 = new dropdownlist()             {                 id = "opportunitymappingddl" + index,             };              htmltablecell td = new htmltablecell()             {                 id = "tdmapping" + index             };             td.controls.add(ddl);              htmltablecell td2 = new htmltablecell()             {                 id = "tdoppmapping" + index             };             td2.controls.add(ddl2);              htmltablerow tr = new htmltablerow()             {                 id = "trmapping" + index             };             tr.cells.add(td);             tr.cells.add(td2);              tblfilemapping.rows.add(tr);             index++;         }     } 

i call method in page_load controls not retain previous data , selected values.

so couple of things wrong here:

• on page_load controls recreated state not restored.
• for technical reasons, project manager mentioned should not use session state store anything.
• another pm advised me controls should regenerated on page_init. since i'm storing control data in viewstate, isn't possible because viewstate isnt ready , data null.

can advise on how succesfully restore viewstate these dynamically generated controls. i've tried searching , tried bunch of solutions online, nothing have tried seems work.

thanks!

you doing right, have recreate controls datasource , rebinding controls again. without beeing done, creating controls not match previous. can call first method that.