I have a DataGrid and everytime I change value of it's embeded dropdwonlist I get: "System.Web.HttpException: The IListSource does not contain any data sources."

I have a data grid which loads fine:

Name column is editable. I have a dropdownlist these :

DataDataGrid gets its value from a table.

(Select Name, Address From Persons)

Dropdown list also gets list of names from the same table.

So DataGrid and dropdownlist are bound to 2 different datasets.

Here is my code for dataGrid"

<Columns>

<ASP:ButtonColumn Text="Delete" CommandName="Delete"></ASP:ButtonColumn>

<asp:EditCommandColumn ButtonType="LinkButton" UpdateText="Update" CancelText="Cancel" EditText="Edit"></asp:EditCommandColumn>

<ASP:TemplateColumn HeaderText="Name" SortExpression="FY" HeaderStyle-HorizontalAlign="center" HeaderStyle-Wrap="True">
                        <ItemStyle Wrap="false" HorizontalAlign="left" />
<ItemTemplate>
<ASP:Label ID="Name" Text='<%# DataBinder.Eval(Container.DataItem, "Name") %>' runat="server"/>
</ItemTemplate>
<EditItemTemplate>
  <ASP:DropDownList id="ddlName" cssClass="DropDownList" runat="server" datasource="<%#allNames%>" DataTextField= "Name" DataValueField="ID" Defaultvalue='<%# DataBinder.Eval(Container.DataItem, "ID") %>' OnPreRender="SetDefaultListItem" accessKey="I" AutoPostBack="true" />
</EditItemTemplate>
</ASP:TemplateColumn>

<asp:BoundColumn DataField="Address" ReadOnly="True" HeaderText="Address"></asp:BoundColumn>


</Columns>

Error happens here :

 dg.DataSource = ds
 dg.DataBind()

Any ideas how to solve this issues? All I want is a DataGrid with a editable column ,which can be edited by choosing one of the value of in a dropdownlist.