c# - Not able to store information while postback after creating dynamic dropdown in ASP.NET -

here code

after button 2 click event creating dropdown in table rows when try save button 1 click event disappear. have not find solution regarding this. have used find control view state etc it's not helping.

i want store selected values of dropdown after button_1 click event starts.

public partial class studentclasssectionmapping : system.web.ui.page     {         protected void page_load(object sender, eventargs e)         {             if(!ispostback)             {                 classcode.enabled = false;          }     }      protected void button2_click(object sender, eventargs e)     {         updatemodalshowflag.value = "true";         check.value = "true";         createtablerows();     }      private void createtablerows()     {          long h = long.parse(linkbuttonidcarrier.value);         list<studentsclasssectionmapping.studentsclasssectionmappingform> allstudentsinclass = studentsclasssectionmapping.getstudentsinclass(h);         classmaster.classmasterform classcode = schoolclasses.getinfo(h);         classcode.text = classcode.ccode;         list<studentsclasssectionmapping.studentsclasssectionmappingform> allsectionsinclass = studentsclasssectionmapping.getsectionsinclass(h);         foreach (studentsclasssectionmapping.studentsclasssectionmappingform studentlist in allstudentsinclass)         {             tablerow row = new tablerow();             tablecell cell1 = new tablecell();             tablecell cell2 = new tablecell();             tablecell cell3 = new tablecell();             dropdownlist t = new dropdownlist();             t.items.add("no section");             foreach (studentsclasssectionmapping.studentsclasssectionmappingform sectionlist in allsectionsinclass)             {                 t.items.add(sectionlist.sssection);                 t.items[t.items.count - 1].value = sectionlist.sssectionid.tostring();             }             t.attributes.add("class", "form-control");              t.id = studentlist.ssstudentid.tostring();             cell1.text = studentlist.ssname;             cell2.text = studentlist.ssregistrationnumber;             cell3.controls.add(t);             row.cells.add(cell1);             row.cells.add(cell2);             row.cells.add(cell3);             table1.rows.add(row);         }     }     protected void button1_click(object sender, eventargs e)     {         createtablerows();         long h = long.parse(linkbuttonidcarrier.value);         list<studentsclasssectionmapping.studentsclasssectionmappingform> allstudentsinclass = studentsclasssectionmapping.getstudentsinclass(h);         foreach (studentsclasssectionmapping.studentsclasssectionmappingform studentlist in allstudentsinclass)         {              dropdownlist d = table1.findcontrol(studentlist.ssstudentid.tostring()) dropdownlist;             if (d != null)             {                   if (d.selectedindex != 0)                 {                     studentsclasssectionmapping.studentsclasssectionmappingform studentsectionmapping = new studentsclasssectionmapping.studentsclasssectionmappingform();                     studentsectionmapping.ssclassid = h;                     studentsectionmapping.ssstudentid = studentlist.ssstudentid;                     studentsectionmapping.ssstudentid = long.parse(d.selecteditem.value);                     studentsclasssectionmapping.addsectionstudentmapping(studentsectionmapping);                 }                 else                  {                     studentsclasssectionmapping.studentsclasssectionmappingform studentsectionmapping = new studentsclasssectionmapping.studentsclasssectionmappingform();                     studentsectionmapping.ssclassid = h;                     studentsectionmapping.ssstudentid = 0;                     studentsectionmapping.ssstudentid = 0;                     studentsclasssectionmapping.addsectionstudentmapping(studentsectionmapping);                 }             }         }     } 

it vanished/disappear because added dynamically on page. if want or want reserver control dynamically created need recreate again , need add dynamically.

here example of how can : how create controls dynamically in asp.net , retrieve values it