Question

I had trouble getting the value a user selected from a DropDownList. I’ve figured out that I require a postback to get my values to reset and be able to get reassigned. (I’ve tried things like ClientIDMode=”static” in the page control and doing “var dropDownList= $(<%= ddlNewCaseFiles.ClientID %>).val() ) however nothing seems to work. So I implemented this in my header:

    <script runat="server">
    protected void ddlCaseFilesNew_SelectedIndexChanged(object sender, EventArgs e)
    {
        hidNewCaseFile.Value = ddlCaseFilesNew.SelectedItem.Value;
    }
</script>

and it seems to be getting the updated values selected. But for some reason when I click on an item it send me to the “Cannot find Resource” page. I’m guessing if I add an Updatepanel to my DropDownList it will probably fix it?(since it is only posting back my dropDownList). But I am having trouble with it.

this is my DropDownlist:

<div id="ddlFiles">
        <label>
            Select new CaseFile:</label>
        <asp:DropDownList runat="server" ID="ddlCaseFilesNew" DataSourceID="dsCaseFiles"
            DataTextField="Display" DataValueField="FileID" 
            OnPreRender="ddl_PreRender" Width="300px" AutoPostBack="true" 
            onselectedindexchanged="ddlCaseFilesNew_SelectedIndexChanged"/>
    </div>

I’ve tried to implement it here but I’m getting a “UpdatePanel does not have a property name called “dropDownList””. Any help would be great fully appreaciated.:

<asp:UpdatePanel runat="server" ID="UpdatePanel1">
        <asp:DropDownList runat="server" ID="ddlCaseFilesNew" DataSourceID="dsCaseFiles"
            DataTextField="Display" DataValueField="FileID" OnPreRender="ddl_PreRender" Width="300px"
            AutoPostBack="true" onselectedindexchanged="ddlCaseFilesNew_SelectedIndexChanged" />
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="ddlCaseFilesNew" EventName="SelectedIndexChanged" />
        </Triggers>
    </asp:UpdatePanel>

Pre_render as requested:

 protected void ddl_PreRender(object sender, EventArgs e)
{
    DropDownList ddl = (DropDownList)sender;
    try
    {
        if (ddl.Items[0].Value != "-1")
            ddl.Items.Insert(0, new ListItem("--Select--", "-1"));
    }
    catch
    {
        ddl.Items.Insert(0, new ListItem("--Select--", "-1"));
    }

}

Answer 1

if you wanna have it in the update panel 

you should add the  the hidNewCaseFile control inside ContentTemplate  tags

Example : 


 in the header 

  <script runat="server">
        protected void   DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            hidNewCaseFile.Text = ddlCaseFilesNew.SelectedItem.Value;
        }



    </script>

in the body 




    <asp:UpdatePanel ID="UpdatePanel1" runat="server">

        <ContentTemplate>

            <asp:Label runat="server" ID="hidNewCaseFile" Text="Label"></asp:Label>
            <asp:DropDownList ID="ddlCaseFilesNew" AutoPostBack="true" runat="server" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
        <asp:ListItem>Uae</asp:ListItem>
        <asp:ListItem>KSA</asp:ListItem>
        <asp:ListItem>Lebanon </asp:ListItem>


    </asp:DropDownList>



        </ContentTemplate>


    </asp:UpdatePanel>

Also make sure that you have <asp:ScriptManager runat="server"> </asp:ScriptManager >

before you use the update panel