Launching modal popup on body onload

Question

I have an AJAX modalpopup which I would like to launch when a page loads. Currently, I have the following in my Page_Load:

HtmlGenericControl myBody = (HtmlGenericControl)Master.FindControl("thebody");
myBody.Attributes.Add("onload", "openMP();")

This successfully injects the onload function (I can tell by looking at the source). However, the onload function never seems to fire. Any advice would be helpful. Thanks.

* Changes following question *

Relevant code in master page:

<asp:LoginView ID="LoginView1" runat="server">
          <LoggedInTemplate>
          <a href="logout.aspx">

Relevant code in child page:

    if (!Page.IsPostBack)
    {
        Page.ClientScript.RegisterStartupScript(this.GetType(), "MyScript", "openMP();", true);
        Response.Write("Test");
    }

Answer 1

You may want to look at ClientScript.RegisterStartupScript. Here's an example of how you could implement it:

Page.ClientScript.RegisterStartupScript(this.GetType(), "MyScript",
   "openMP();", true);

Within the Page_Load event, this would fire every time the page is loaded.

EDIT: For clarity sake, here's an example of what I'm talking about in my comment:

ASPX Page Code-behind:

protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
        Page.ClientScript.RegisterStartupScript(this.GetType(), "MyScript",
            "openMP();", true);
}

ASPX Page:

<Form ID="Form1">
.
.
.
</Form>
<Script Language="javascript">
    function openMP() {
        ...
    }
</Script>