Question

EDIT:
Apparently, part of the problem is that while an ASP:GridView has an OnDataBound() event (which you can use in the code-behind), the corresponding HTML table that is produced does NOT, so you can attach that event to JavaScript. (Did I get that right?) So, that’s why I’m having trouble with that bit of the issue. Back to the drawing board.

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I’m a desktop developer (WinForms with VB.NET) transitioning into ASP.NET development. My mind is really bending around the DOM and JavaScript and Session State and all of the stuff that goes along with web development. I’m not stupid, and I’ve done research (including hours of video watching and hundreds of pages of “Intro to ASP.NET” reading), but I keep hitting the wall with what seem to be fairly straightforward problems.

Basically, my current situation can be summed up as follows:

1. I have a page that runs a very long process initiated by the user.
2. The long process can take up to a few minutes , so I want to indicate to the user that SOMETHING is happening.
3. When the process has completed, I either have:
   a. Results to show in a GridView
   b. No results to show
4. If I have results to show, I want to display them.
5. If I have no results to show, I want to show a label to the user that says “No results to show.”

What’s working:

1. I have a basic page where the user selects start and end dates and kicks off the check process.
2. The check process works fine (using LINQ-to-SQL logic developed for a desktop version of this program).
3. I’ve got an UpdatePanel on my page which shows a label and an animated gif to indicate that something’s happening.
4. If I get results, they display appropriately in my GridView.

What’s not working:

1. I’d love to give the user some sort of progress bar to indicate actual progress made toward completion rather than some endlessly-animating gif that doesn’t indicate much at all. I could calculate this value quickly and easily, but can’t figure out how to transfer said value from server to web page.

2. I can’t figure out how to trigger an “unhide” event for the label. The long-running process is in a button’s click event handler, where I run my custom code and generate a DataTable, which I then save as a session variable, assign it as the GridView’s DataSource and call GridView.DataBind(). When I try to determine the contents of the DataTable and hide/reveal the label there, nothing seems to happen.

Problem #2 is really what I need to figure out in order to publish this web site. I’m assuming it involves a JavaScript solution, and I’ve tried some stuff, but I find that I’m truly guessing and don’t have a good grasp on what the solution should resemble.

Here’s the label I’d like to selectively reveal/make visible:

<tr>
    <td colspan="2" align="center">
        <h2><asp:Label runat="server" ID="lblNoMissing" Text="No Missing Documentation Found" Visible="false"></asp:Label></h2>
    </td>
</tr>

Here’s a JavaScript function I’m trying to test:

<script type="text/javascript">
    function databound() {
        var gridViewID = '<%=_gridView1.ClientID%>';
        var labelID = '<%=lblNoMissing.ClientID%>';
        var gridView = document.getElementById(gridViewID);
        if (gridView.rows.length > 0) {
            $get(labelID).style.visibility = "false";
        } else {
            $get(labelID).style.visibility = "true";
        }
    }
</script>

Problem: This fails (databound not a member of Default.aspx):

<asp:GridView ID="_gridView1" runat="server"
    AllowSorting="True" AutoGenerateColumns="False" CellPadding="4" 
    ForeColor="#333333" GridLines="Horizontal" PageSize="20" OnDataBound="databound();">
// Rest of GridView definition removed
</asp:GridView>

What am I missing?

Thanks!!!!

Answer 1

For problem #1, there are a whole bunch of free Javascript progress bars out there. As for your value that you can’t retrieve, try this:

<asp:Label ID="ProgressValue" runat="server" visible="false" /> 

And in your code behind.

ProgressValue.Text = //Your value from your database. 

And just reference it from your Javascript there.

For your second problem, can’t you just do in your code behind (written in C#)

//Process here
if(IDofGridView.Rows != null) 
{
    lblNoMissing.Visible = true; 
}

Or am I missing something?