c# - Empty GridView with dropdownlist having Datatable as it's datasource -

i've form shows empty gridview along add new button. have drop down list in column 1 gets populated database. based on selected dropdown list, query sql database , populate columns 2 , 3. i'm having trouble writing values of dropdown list datatable , add new row. worked when gridview had textboxes adding databound dropdownlist made lot complex. here code:

<asp:gridview id="gridview1" runat="server" showfooter="true" autogeneratecolumns="false">         <columns>         <asp:boundfield datafield="rownumber" headertext="row number" />         <asp:templatefield headertext="item number">             <itemtemplate>                 <asp:dropdownlist id="ddlitemnumber" runat="server" datasourceid="sdssubjects" datatextfield="item_num" datavaluefield="item_num" onselectedindexchanged="index_changed" autopostback="true" ondatabound="adddefaultvalue_databound">                 </asp:dropdownlist>                 <asp:sqldatasource id="sdssubjects" runat="server" connectionstring="<%$ connectionstrings:test%>"                     selectcommand="select item_num tblitemlist"></asp:sqldatasource>                 <asp:requiredfieldvalidator id="reqitemnumber" validationgroup="valgrpcust" controltovalidate="ddlitemnumber" runat="server" errormessage="required"></asp:requiredfieldvalidator>                                                 </itemtemplate>         </asp:templatefield>         <asp:templatefield headertext="description">             <itemtemplate>                 <asp:textbox id="textbox1" runat="server"></asp:textbox>             </itemtemplate>         </asp:templatefield>         <asp:templatefield headertext="unit">             <itemtemplate>                 <asp:textbox id="textbox2" runat="server"></asp:textbox>             </itemtemplate>         </asp:templatefield>         <asp:templatefield headertext="quantity">             <itemtemplate>                  <asp:textbox id="textbox3" runat="server"></asp:textbox>             </itemtemplate>             <footerstyle horizontalalign="right" />             <footertemplate>              <asp:button id="buttonadd" runat="server" text="add new row"                      onclick="buttonadd_click" />             </footertemplate>         </asp:templatefield>         </columns>     </asp:gridview> 

here code behind:

protected void page_load(object sender, eventargs e) {     if (!page.ispostback)     {         setinitialrow();     } } protected void buttonadd_click(object sender, eventargs e) {     addnewrowtogrid(); }  protected void adddefaultvalue_databound(object sender, eventargs e) {     dropdownlist list = sender dropdownlist;      if (list != null)     {         list.items.insert(0, "--select one--");     } }  private void setinitialrow() {     datatable dt = new datatable();     datarow dr = null;     dt.columns.add(new datacolumn("item number", typeof(string)));     dt.columns.add(new datacolumn("description", typeof(string)));     dt.columns.add(new datacolumn("unit", typeof(string)));     dt.columns.add(new datacolumn("quantity", typeof(string)));     dr = dt.newrow();     dr["item number"] = string.empty;     dr["description"] = string.empty;     dr["unit"] = string.empty;     dr["quantity"] = string.empty;     dt.rows.add(dr);      //store datatable in viewstate     viewstate["currenttable"] = dt;      gridview1.datasource = dt;     gridview1.databind(); } private void addnewrowtogrid() {     int rowindex = 0;      if (viewstate["currenttable"] != null)     {         datatable dtcurrenttable = (datatable)viewstate["currenttable"];         datarow drcurrentrow = null;         if (dtcurrenttable.rows.count > 0)         {             (int = 1; <= dtcurrenttable.rows.count; i++)             {                 //extract textbox values                 dropdownlist ddllist1 = (dropdownlist)gridview1.rows[rowindex].findcontrol("ddlitemnumber");                 textbox box1 = (textbox)gridview1.rows[rowindex].findcontrol("textbox1");                 textbox box2 = (textbox)gridview1.rows[rowindex].findcontrol("textbox2");                 textbox box3 = (textbox)gridview1.rows[rowindex].findcontrol("textbox3");                  drcurrentrow = dtcurrenttable.newrow();                 //drcurrentrow["ro wnumber"] = + 1;                 dtcurrenttable.rows[i - 1]["item number"] = ddllist1.selecteditem.text;                 dtcurrenttable.rows[i - 1]["description"] = box1.text;                 dtcurrenttable.rows[i - 1]["unit"] = box2.text;                 dtcurrenttable.rows[i - 1]["quantity"] = box3.text;                  rowindex++;             }             dtcurrenttable.rows.add(drcurrentrow);             viewstate["currenttable"] = dtcurrenttable;              gridview1.datasource = dtcurrenttable;             gridview1.databind();         }     }     else     {         response.write("viewstate null");     }      //set previous data on postbacks     setpreviousdata(); } private void setpreviousdata() {     int rowindex = 0;     if (viewstate["currenttable"] != null)     {         datatable dtcurrenttable = (datatable)viewstate["currenttable"];         datatable dt = (datatable)viewstate["currenttable"];         if (dt.rows.count > 0)         {             (int = 0; < dt.rows.count; i++)             {                 dropdownlist ddllist1 = (dropdownlist)gridview1.rows[rowindex].findcontrol("ddlitemnumber");                 textbox box1 = (textbox)gridview1.rows[rowindex].findcontrol("textbox1");                 textbox box2 = (textbox)gridview1.rows[rowindex].findcontrol("textbox2");                 textbox box3 = (textbox)gridview1.rows[rowindex].findcontrol("textbox3");                  ddllist1.selecteditem.text = dt.rows[i]["item number"].tostring();                 box1.text = dt.rows[i]["description"].tostring();                 box2.text = dt.rows[i]["unit"].tostring();                 box3.text = dt.rows[i]["quantity"].tostring();                  rowindex++;             }         }     } }  protected void index_changed(object sender, eventargs e) {     dropdownlist ddlitemnumber = (dropdownlist)sender;     gridviewrow grdrdropdownrow = ((gridviewrow)ddlitemnumber.parent.parent);     int index = grdrdropdownrow.rowindex;             //lblmessage.text = ddlitemnumber.selecteditem.text;     dataset mydataset = getdata("select description, unit tblitemlist item_num='" + ddlitemnumber.selecteditem.text.trim     () + "'");     grdrdropdownrow.cells[1].text = mydataset.tables[0].rows[0]["description"].tostring();      grdrdropdownrow.cells[2].text = mydataset.tables[0].rows[0]["unit"].tostring();     datatable dt = (datatable)viewstate["currenttable"];     if (dt.rows.count > 0)     {         (int = 0; < dt.rows.count; i++)         {             dt.rows[i]["item number"] = grdrdropdownrow.cells[1].text;             dt.rows[i]["description"] = grdrdropdownrow.cells[2].text;             dt.rows[i]["unit"] = grdrdropdownrow.cells[3].text;             dt.rows[i]["quantity"] = grdrdropdownrow.cells[4].text;         }     }     setpreviousdata(); }  private dataset getdata(string query) {     string constring = configurationmanager.connectionstrings["test"].connectionstring;     sqlcommand cmd = new sqlcommand(query);     using (sqlconnection con = new sqlconnection(constring))     {         using (sqldataadapter sda = new sqldataadapter())         {             cmd.connection = con;             sda.selectcommand = cmd;             using (dataset ds = new dataset())             {                 sda.fill(ds);                 return ds;             }         }     } } 

thanks clues , time.

joe