asp.net dropdownlist - asp.net

Question

I have two dropdownlists for a search, the 1st list is for the city and the second is for the area within the selected city. I would like to add a default value in the 2nd dropdownlist that will search ALL of the areas by default unless a specific area is selected from the list that contains the areaID for a specific search.
<asp:DropDownList ID="DropDownList1" runat="server"
DataSourceID="SqlDataSource1" DataTextField="cityName" AutoPostBack="true" DataValueField="cityID">
</asp:DropDownList>
<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
SelectCommand="SELECT * FROM [Cities]"></asp:SqlDataSource>
<asp:DropDownList ID="DropArea" runat="server" DataSourceID="SqlArea"
DataTextField="areaName" DataValueField="areaID">
</asp:DropDownList>
<asp:SqlDataSource ID="SqlArea" runat="server"
ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
SelectCommand="SELECT * FROM [area] WHERE ([cityID] = #cityID)">
<SelectParameters>
<asp:ControlParameter ControlID="DropDownList1" DefaultValue="0" Name="cityID"
PropertyName="SelectedValue" Type="Int16" />
</SelectParameters>
</asp:SqlDataSource>
<asp:Button ID="Button1" runat="server" Text="Search" onclick="Button1_Click" />

Answer 1

Bind the second from code behind. Create a data table and insert the Select text at the begining and bind the datatable to the DDL.
DataTable dt =
DataRow dr = dt.NewRow()
dr["areaName"] = "All";
dr["SqlArea"] = "All";
tbldata.Rows.InsertAt(dr,0);
DropArea.DataSource = dt;
DropArea.DataBind();

Answer 2

You can try to add for second dropdownlist OnDataBound="DropArea_DataBound" event.
And use in code:
protected void DropArea_DataBound(object sender, EventArgs e)
{
DropArea.Items.Insert(0, new ListItem() {Value = "-1", Text = "ALL"});
}
And then when you handle click event, check:
var value = DropArea.SelectedItem.Value;
if(string.equals(value, '-1')
{
use your logic here
}
Hope it will help with your problem.
Best regards, Dima.

Answer 3

Chris,
I got the idea below from an answer HERE, but basically you want to modify your query to be in the form of the following:
Your Original:
SELECT * FROM [Cities]
Change To:
SELECT City FROM [Cities]
UNION ALL
SELECT 'ALL'
Old question, but you never found an answer.