c# - Capture Checked Value From Data Grid -

i continue error of

object not set instance of object

what need change code can execute succesfully?

html

<td valign="top" style="text-align: left; width: 200px;"> <asp:gridview runat="server" id="datagridtest" autogeneratecolumns="false" gridlines="both" showfooter="true" > <columns> <asp:boundfield datafield="field1" headertext="1st set" /> <asp:boundfield datafield="field2" headertext="2nd set" /> <asp:templatefield>     <itemtemplate>         <asp:label runat="server" text='<%#eval("categoryid") %>' id="managerid" visible="false"></asp:label>      </itemtemplate>     <itemtemplate>         <asp:checkbox id="checked" runat="server" autopostback="false" checked='<%# convert.toboolean(eval("checked")) %>' />     </itemtemplate> </asp:templatefield> </columns> </asp:gridview>                                 <asp:button runat="server" id="btnchecked" cssclass="buttons" text="add" onclick="btnc_click" /> </td> 

c#

protected void btnc_click(object sender, eventargs e) { try {     foreach (gridviewrow row in datagridtest.rows)     {         string id = ((label)row.findcontrol("managerid")).text;         if (row.rowtype == datacontrolrowtype.datarow)         {             checkbox chk = (checkbox)row.findcontrol("checked");             if (chk.checked) {}             else {}         }     } } catch (exception exception) { throw exception; } } 

in html setting gridviews id

id="datagridtest"

but in code behind use "dgrd".this may root problem.