I'm brand spanking new to DNN development. In fact, if anyone wants to throw links at me on documents that layout DNN's framework or any other great literature that will get me up to speed on developing modules for DNN, go ahead. But, here's the reason for my post...

Firstly, I'm working in C#.

I'm trying to do a PostBack to the same page, but trigger that PostBack by Javascript function (which is called by a Flash function, because apparently there's not a way to run a C# function from Flash?). Anyway, for this application, I only need to pass one hidden value. Then compare that value within an IsPostBack check of the Page_Load procedure to display an object and/or run a LINQ insert.

I've been working on this for a while, and I can't seem to get it to work...

1. I don't know how to trigger the PostBack with Javascript.

2. I'm not sure how to consume the passed value in the code behind.

3. I'm not sure that the page isn't just refreshing.

Since all that relies on each other, it makes it about impossible to trouble shoot... any help would be MUCH appreciated.

As a postback you wouldn't actually be grabbing it from the QueryString collection.  In fact, because you created it as a server object (runat=server) you can merely access it directly via code as watchKey.Value.  So something more like:

protected void Page_Load(object sender, EventArgs e)
{
  // note, not !IsPostBack because that means on the initial load of the page
  if (IsPostBack)
  {
    // TODO: do something with your value
    string feedback = watchKey.Value;
    // optional way to access value: Request.form["watchKey"]
  }
}

EDIT: I noticed that you have this in a "subform".  ASP.NET, in general and without hacks, only supports a single form tag per page.  DotNetNuke will automatically insert the form tag (from default.aspx) and then injects your skin and modules inside that form.  Since your form is marked as runat=server and visible=false I think that is why no error is being thrown.  Just pull that extra form out and if you want to logically group those components slap them into a div or asp:Panel.

It *is* possible to get the element by id as such however you need to use the CLIENTID of the component, not the "ID".  The thing here is that because of it's dynamic nature, ASP.NET allows you to arbitrarily include controls as children of other controls and assign a name/ID that you can relate to.  However, what if another control on the page already has the same name?  This is where the "naming container" feature of ASP.NET comes in.  Lets say I have a DataList named "listEmployees" and each row in the list has a template with a textbox, image, and checkbox which I name "textName", "imgPhoto", and "chkActive" respectively.  Each row can't possibly name their control that in reality because we'd have naming conflicts so ASP.NET proceeds to help us out with that naming it something like listEmployees_ctl1_textName, listEmployees_ctl1_imgPhoto, listEmployees_ctl1_chkActive and so on.  You would use a listEmployees.Items[x].FindControl("textName") to retrieve a reference to that particular textbox for that particular employee record.

So to relate that to DNN and tie it all in.  DNN is composed of UserControls which, by their very nature, function as Naming Containers.  If you were to view source on a DNN page you'd see things named like "dnn_ctr450_dnnTITLE_lblTitle" (which is the TITLE element for module #450 on my page).  Pretty nasty and not easy to work with.  However, enter ClientID.  *ALL* controls have a property for ClientID which is their generated naming container + given ID.  Lets apply that to your sample now (using server side script to inject the ClientID into your clientside script):

<script type="text/javascript">

function writeStatus(){
    // End!"); 
    document.getElementById("<%= submitStatusBtn.ClientID %>").click();
}

</script>

As you can see I injected the clientID of your server-side control into your clientside script.  For more information about this I googled and came up with this page by one James Gregory.  His method is in no way the standard but one that I think is pretty nice.  I tend to just inject some javascript during OnPreRender that stores the namespace into a javascript variable (so I'd output to the page from the module itself something to the effect of: var _ns = this.ClientID and then my javascript would say document.getElementById(_ns + "submitStatusBtn").  There are plenty of ways to accomplish it, that's just one I've chosen to use.

Hopefully that helps you on the javascript side?