DataBound DropDownList in DataGrid - order of binding

Question

I have a DataGrid that looks like this (slightly simplified here):

<asp:DataGrid ID="grdQuotas" runat="server" AutoGenerateColumns="False">
    <HeaderStyle CssClass="quotas-header" />
    <Columns>
        <asp:TemplateColumn>
            <HeaderTemplate>
                Max order level</HeaderTemplate>
            <ItemTemplate>
                <asp:DropDownList ID="ddlMaxOrderLevel" runat="server" DataSourceID="xdsOrderLevel"
                    DataTextField="Text" DataValueField="Value" SelectedValue='<%# Bind("MaxOrderLevel") %>'>
                </asp:DropDownList>
            </ItemTemplate>
        </asp:TemplateColumn>
    </Columns>
</asp:DataGrid>

<asp:XmlDataSource ID="xdsOrderLevel" runat="server" DataFile="~/App_Data/OrderLevels.xml">
</asp:XmlDataSource>

In my Page_Load event handler I am creating a DataTable containing default values and DataBinding it to the DataGrid.

The problem is that this is taking place before the DropDownList ddlMaxOrderLevel has been bound to its DataSource, so I get a runtime error telling me that the SelectedValue cannot be set.

If ddlMaxOrderLevel was not in a DataGrid I could just call DataBind() on it. However I cannot do that in this scenario - since it is in an ItemTemplate.

Can anyone suggest a workaround or alternate approach?

Answer 1

You could do the Databinding of the DropDownlist in the Databound event of the DataGrid.

Edit: I will give you an example that i have tested:

 protected void dg_ItemDataBound(object sender, DataGridItemEventArgs e)
    {
        if (e.Item.ItemType != ListItemType.Header && e.Item.ItemType != ListItemType.Footer)
        {
            DropDownList dl = (DropDownList)((DataGridItem)e.Item).FindControl("ddlMaxOrderLevel");

            dl.DataSource = levels;
            dl.DataBind();

            dl.SelectedValue = ((DataRowView)e.Item.DataItem)["number"].ToString();


        }

    }

Answer 2

Create another DataSource and bind it to the DataGrid. Where the SelectMethod would return the default values in a simple object.

Then all the binding should happily work together.