Edit command erroring out in gridview - asp.net

Question

I'm unable to identify the problem which is causing the edit command to fail
GridView Code
<asp:GridView ID="GridView1" runat="server" AllowPaging="True"
AllowSorting="True" AutoGenerateColumns="False" CellPadding="4"
DataKeyNames="Requestid" DataSourceID="SqlDataSource1" ForeColor="#333333"
GridLines="None" Height="321px" Width="604px">
<AlternatingRowStyle BackColor="White" />
<Columns>
<asp:CommandField ShowEditButton="True" UpdateText="Submit" />
<asp:BoundField DataField="Requestid" HeaderText="Requestid" ReadOnly="True"
SortExpression="Requestid" />
<asp:BoundField DataField="Receiveddate" HeaderText="Receiveddate"
SortExpression="Receiveddate" />
<asp:BoundField DataField="Ctname" HeaderText="Ctname"
SortExpression="Ctname" />
<asp:TemplateField HeaderText="Requestor" SortExpression="Requestor">
<EditItemTemplate>
<asp:DropDownList ID="DropDownList1" runat="server"
DataSourceID="SqlDataSource2" DataTextField="analystname"
DataValueField="contact_id" SelectedValue='<%# Bind("Requestor") %>'>
</asp:DropDownList>
<asp:SqlDataSource ID="SqlDataSource2" runat="server"
ConnectionString="<%$ ConnectionStrings:Customers %>" SelectCommand="SELECT [contact_id], [first_name]+ space(1)+ [last_name] as analystname FROM [contact]
order by contact_id"></asp:SqlDataSource>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Bind("Requestor") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
</Columns>
<EditRowStyle BackColor="#CC3300" />
<FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
<HeaderStyle BackColor="#CBB06D" Font-Bold="True" ForeColor="White" />
<PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" />
<RowStyle BackColor="#EFF3FB" />
<SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" />
<SortedAscendingCellStyle BackColor="#F5F7FB" />
<SortedAscendingHeaderStyle BackColor="#6D95E1" />
<SortedDescendingCellStyle BackColor="#E9EBEF" />
<SortedDescendingHeaderStyle BackColor="#4870BE" />
</asp:GridView>
<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="<%$ ConnectionStrings:Customers %>" SelectCommand="SELECT RR.Requestid,Convert(varchar(20),RR.Receiveddate,100) as Receiveddate,RR.Ctname,C.First_Name +Space(1) + C.Last_NAME as Requestor from report_request_draft RR inner join Contact C on RR.requestor = C.contact_id
where clonedfromid is not null"
UpdateCommand="UPDATE [REPORT_REQUEST_DRAFT] SET [REQUESTOR] = #Requestor WHERE [requestid] = #requestid">
</asp:SqlDataSource>
When i click on the edit command button it gives me the below error
Error
'DropDownList1' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.ArgumentOutOfRangeException: 'DropDownList1' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value

Answer 1

The DropDownList can't be bound in this way. By using the SelectedValue binding as you have it, it requires that the DropDownList is bound before the GridView is bound, but that is a logical impossibility since the DropDownList can't be bound until the GridView has completed its binding. You should put this logic in the code behind with the RowDataBound event. At that point, you should manually bind your DropDownList and then set its SelectedValue property.

Answer 2

Consider the following link which will help you to solve your problem and it also shows you how to bind EditItemTemplet perfectly in grid View. I condenser you to use this link for better understand grid view.