onbeforeunload error

David · Sep 5, 2006

I am using a process to warn users when they leave a page that there have
been changes made. I took the example directly from Microsoft example I
found in searching for help on the event onbeforeunload. I have the event
inside the BODY element in my aspx page and it seems to work just fine.
However, I still get a flash of a page error in the lower left corner of my
browser and the Visual Studio 2005 "souce" page shows the event name
underlined with mouseover message "Validation (XHTML 1.0 Transitional):
Attribute 'onbeforeunload' is not a valid attribute of element 'body'."

Is there anything I can do to get rid of this error? Thanks.

David

Teemu Keiski · Sep 5, 2006

Hi,

yes it is not valid.

You can change the body tag to be server-side object

<body id="BodyTag" runat="server">

and then add the call via Attributes collection in code:

BodyTag.Attributes["onbeforeunload"] = "closeIt()";

And with ASP.NET 2.0, you can also use expando attribute mechanism to
preserve compatibility with rendered markup. Then just have <body> also with
ID and runat="server" and the relevant code

Page.ClientScript.RegisterExpandoAttribute(BodyTag.ClientID,
"onbeforeunload", "closeIt");
string script=String.Format("eval(\"{0}.onbeforeunload = \" +
{0}.onbeforeunload + \";\");",BodyTag.ClientID);
Page.ClientScript.RegisterStartupScript(this.GetType(), "evaling",
script, true);

(closeIt is function which is called when onbeforeunload fires)

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onbeforeunload error

David

Teemu Keiski

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