Hidden View Data

I have a dropdownlist that when you select the value, allows a select query to be used in the gridview. I am trying to pass the query results to a hidden field and then pass those values to a popup. I have the popup function working and the select but the problem lies in the hidden field. Whever I try to capture the value it gives me an error. Thanks for the help ^_^

Here is the vb part

Imports System

Imports System.Data

Imports System.Configuration

Imports System.Collections

Imports System.Web

Imports System.Web.Security

Imports System.Web.UI

Imports System.Web.UI.WebControls

Imports System.Web.UI.HtmlControls

Imports System.Web.UI.WebControls.WebParts

Partial Class _Default
    Inherits System.Web.UI.Page

    Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles DropDownList1.SelectedIndexChanged
        ClientScript.RegisterStartupScript([GetType](), "a", "ButtonClick()", True)
        HiddenField1.Value = GridView1.SelectedValue

        Dim strQuery = "SELECT [text_course], [text_course_id], [text_contact_hours], [text_credit_hours], [text_des] FROM [Text] WHERE ([text_course] = @text_course)"
    End Sub
End Class

Html Source:

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<HEAD>
<TITLE>Popup Example</TITLE>

<SCRIPT LANGUAGE="JScript">
var oPopup = window.createPopup();
function ButtonClick()
{
    var oPopBody = oPopup.document.body;
    oPopBody.style.backgroundColor = "lightyellow";
    oPopBody.style.border = "solid black 2px";
    oPopBody.innerHTML = "Click outside <B>popup</B> to close.";
    oPopup.show(100, 100, 180, 25, document.body);
}
</SCRIPT>
</HEAD>

<BODY>
<form runat="server">
SELECT [text_course], [text_course_id], [text_contact_hours], [text_credit_hours], [text_des] FROM [Text] WHERE ([text_course] = @text_course)
<button id="alpha" onmouseover="ButtonClick()" style="left: 59px; position: absolute; top: 157px">Move OVer</button>
     
    <asp:SqlDataSource ID="SqlDataSource3" runat="server" ConnectionString="<%$ ConnectionStrings:Con+PorjectConnectionString1 %>"
        ProviderName="<%$ ConnectionStrings:Con+PorjectConnectionString1.ProviderName %>"
        SelectCommand="SELECT [text_course], [text_course_id] FROM [Text] WHERE ([text_course] = @text_course)">
        <SelectParameters>
            <asp:ControlParameter ControlID="DropDownList1" Name="text_course" PropertyName="SelectedValue"
                Type="String" />
        </SelectParameters>
    </asp:SqlDataSource>
       
    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="SqlDataSource3" BackColor="#CCCCCC" BorderColor="#999999" BorderStyle="Solid" BorderWidth="3px" CellPadding="4" CellSpacing="2" ForeColor="Black" style="left: 63px; position: absolute; top: 202px">
        <Columns>
            <asp:BoundField DataField="text_course" HeaderText="Course Name" SortExpression="text_course" />
            <asp:BoundField DataField="text_course_id" HeaderText="Course ID" SortExpression="text_course_id" />
            <asp:CommandField ShowSelectButton="True" />
        </Columns>
        <FooterStyle BackColor="#CCCCCC" />
        <RowStyle BackColor="White" />
        <SelectedRowStyle BackColor="#000099" Font-Bold="True" ForeColor="White" />
        <PagerStyle BackColor="#CCCCCC" ForeColor="Black" HorizontalAlign="Left" />
        <HeaderStyle BackColor="Black" Font-Bold="True" ForeColor="White" />
    </asp:GridView>
    <asp:DropDownList ID="DropDownList1" runat="server" DataSourceID="SqlDataSourcetest"
        DataTextField="text_course" DataValueField="text_course" Style="left: 206px;
        position: absolute; top: 159px" Font-Size="Medium" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" AutoPostBack="True">
    </asp:DropDownList>
    <asp:SqlDataSource ID="SqlDataSourcetest" runat="server" ConnectionString="Data Source=PRIVATE-DE89F9E;Initial Catalog=Con+Porject;Integrated Security=True"
        ProviderName="System.Data.SqlClient" SelectCommand="SELECT [text_course] FROM [Text]">
    </asp:SqlDataSource>
    <asp:SqlDataSource ID="SqlDataSource1" runat="server"></asp:SqlDataSource>
<BUTTON onclick="ButtonClick()" style="left: 76px; position: absolute; top: 91px">Click Me!</BUTTON>
    <input id="Hidden1" type="hidden" runat="server" />
    <asp:HiddenField ID="HiddenField1" runat="server" />
       
    <asp:Label ID="Label1" runat="server" Text="sdf"></asp:Label>
    </form>
</BODY>
</HTML>

Re: Hidden View Data

Where are you capturing the value from the hidden field? Please paste that code as I am unable to find it in the code you pasted.

-Vivek