Populating cascading dropdownlist inside repeater

Question

I have two dropdownlists inside a repeater. And based on the value I pick in the first dropdownlist the second needs to get populated (both need to be populated from the DB via stored proc). Any help on this Please.

I am adding the code I have so far but it's not completely correct

<asp:Repeater ID="rpt" runat="server" OnItemDataBound="rpt_ItemDataBound">
                        <ItemTemplate>
                             <tr>
                                <td style="width: 40%; text-align: left">
                                    <asp:DropDownList ID="ddlOne" runat="server" Width="150px" OnSelectedIndexChanged="PopulateSecondDropDown_selectIndexchanged"
                                        AutoPostBack="true">
                                    </asp:DropDownList>
                                </td>
                                </td>
                                <td style="width: 40%; text-align: left">
                                    <asp:DropDownList ID="ddlTwo" runat="server" Width="150px">
                                    </asp:DropDownList>
                                </td>
                            </tr>
                        </ItemTemplate>
                    </asp:Repeater>

<asp:Button ID="Save" runat="server" Text="Save" OnClick="Save_Values_Click"/>

On Page Load doing this

    rpt.ItemDataBound += new RepeaterItemEventHandler(rpt_ItemDataBound);
    rpt.DataSource = ListForFirstDropDown.GetDropDownList;   // this returns values only for the first dropdownlist
    rpt.DataBind();






   protected void rpt_ItemDataBound(object source, RepeaterItemEventArgs e)
    {
        if (e.Item.ItemType == ListItemType.Item | e.Item.ItemType == ListItemType.AlternatingItem)
        {
                            // not sure how to handle this here

        }
    }




public void PopulateSecondDropDown_selectIndexchanged(object sender, EventArgs e)
        {
            ddlTwo.Items.Clear();
            int ID = Convert.ToInt32(ddlOne.Text);
            LoadSecondDropDown(ID);
        }

        private void LoadSecondDropDown(int ID)
        {
                    rpt.DataSource = ListForSecondDropDown.GetDropDownList(ID);   // this returns values only for the second dropdownlist
            rpt.DataBind();
        }

Answer 1

With an SQLDataSource, you can use SelectParameters to define criteria used in the select statement. This allows you to use a number of sources for parameter value, including another control on the page.

Here's an example of an SQLDataSource populating a drop down list, whose selected value is used in another data source and list:

<asp:SqlDataSource 
    runat="server"
    ID="firstDataSource"
    ConnectionString="<%$ connectionStrings:MyConnectionString %>"
    SelectCommand="SELECT DISTINCT item1 FROM table" />
<asp:DropDownList 
    runat="server" 
    ID="itemList" 
    DataSourceID="firstDataSource" 
    DataValueField="item1" 
    DataTextField="item1" 
    AutoPostBack="true" />

<asp:SqlDataSource 
    runat="server"
    ID="secondDataSource"
    ConnectionString="<%$ connectionStrings:MyConnectionString %>"
    SelectCommand="SELECT item2 FROM table WHERE item1 = @item1">
    <SelectParameters>
        <asp:ControlParameter ControlID="itemList" PropertyName="SelectedValue" Name="item1" />
    </SelectParameters>
</asp:SqlDataSource>
<asp:DropDownList 
    runat="server" 
    DataSourceID="secondDataSource" 
    DataValueField="item2" 
    DataTextField="item2" />

This works within a repeater's ItemTemplate . If the "firstDataSource" needs a key from the repeater item, you can use a hidden field control and another ControlParameter .

<asp:Repeater runat="server" DataSourceID="topDataSource">
    <ItemTemplate>
        <asp:HiddenField runat="server" ID="key" Value='<%# Eval("id") %>' />
        <!-- ... -->
     </ItemTemplate>
</asp:Repeater>