Question

I get the wrong value from my Dropdownlist (ddlCity). I always get the “default” value, the value the list has when the page load. What am I doing wrong?

<asp:DropDownList ID="ddlCountry" runat="server"AutoPostBack="true"></asp:DropDownList>

<asp:DropDownList ID="ddlCity" runat="server"></asp:DropDownList>

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        DataTable CountryTable = CategoryAccess.GetCountry();
        ddlCountry.DataSource = CountryTable;
        ddlCountry.DataTextField = "CountryName";
        ddlCountry.DataValueField = "CountryID";
        ddlCountry.DataBind();
    }
    else
    {
        String CountryID = ddlCountry.SelectedValue;

        DataTable CityTable = CategoryAccess.GetCitysInCountry(CountryID);
        ddlCity.DataSource = CityTable;
        ddlCity.DataTextField = "City";
        ddlCity.DataValueField = "CityID";
        ddlCity.DataBind();
    }
}

protected void btnUpdate_Click(object sender, EventArgs e)
{
    string id = (ddlCity.SelectedItem.Value);
    //This is where id is wrong, unless I choose the first city in the list.
}

Database code:

ALTER PROCEDURE GetCountry
AS          
SELECT        CountryID, CountryName
FROM          tblCountry  



ALTER PROCEDURE GetCitysInCountry
@CountryID INT
AS          
SELECT        tblCitysInCountry.CityID, tblCitysInCountry.CountryID, tblCity.City, tblCountry.CountryName
FROM          tblCitysInCountry LEFT JOIN
                         tblCity ON tblCitysInCountry.CityID = tblCity.CityID LEFT JOIN
                         tblCountry ON tblCitysInCountry.CountryID = tblCountry.CountryID
WHERE         (tblCitysInCountry.CountryID = @CountryID)

Answer 1

Page_Load occurs before the selected index is set during postback. Try moving your second set of databinding code to a more appropriate place – maybe in the event handler that ddlCountry will be invoking (SelectedIndexChanged?)

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There certainly seem to be a lot of hits on Google for “page_load SelectedValue“, which all tend to indicate the value cannot be accessed during Page_Load.