I have overridden OnError method in the page:
public string script;
protected override void OnError(EventArgs e)
{
script = "alert('error');";
}
In the aspx, I have this:
<script type="text/javascript">
$(document).ready(function(){
<%=script %>;
});
</script>
I am simulating an error in Page_Load, but its not firing the alert. If I switch the code from OnError to OnLoad, it works great.
Thoughts?
When you override OnError, you need to clear the error so you mark it as handled, if you don't do this then it will bubble up to Application_Error, trashing any content your page may have rendered..
Try using Server.ClearError
protected override void OnError(EventArgs e)
{
script = "alert('error');";
Server.ClearError(); //Prevent the error from propagating
}
Looking in reflector you can see this..
try
{
this.Context.TempError = e;
this.OnError(EventArgs.Empty);
if (this.Context.TempError == null)
{
return true;
}
}
finally
{
this.Context.TempError = null;
}
Server.ClearError clears that TempError
public void ClearError()
{
if (this._tempError != null)
{
this._tempError = null;
}
...other code..
}
Server.ClearError as you demonstrate. The JS function still doesn't get called and now I see a blank page instead of the error details and the stack traceThe fact that you're throwing an Exception and not handling it in the page with a try/catch means that the page never finishes rendering. Not only are you not getting the output of your script string, you'll probably find you're not getting the $(document).ready() or anything else either as the page isn't rendering.
If you handle the exception like this then the page rendering will complete and your message will display.
try
{
throw new Exception();
}
catch(Exception ex)
{
// log ex.ToString() here
script = "alert('error')";
// decide what to do here - carry on or return
}
In real terms you should try to avoid catching Exception, always try to anticipate which specific exceptions you expect and handle them accordingly. In fact, always try to avoid cases where an Exception can be thrown in the first place - Exceptions should be thrown in exceptional circumstances.
Have a read through this CodeProject article that discusses some best practices regarding exception handling.
LoadControl). I need to ensure that any error from the user control should trigger this JS function. This can include Page Load, Prerender, Oninit or any of those methods. I can't really have try..catch blocks everywhere. Also I have atleast 10 user controls that can be loaded. So, I really dont want to update all these controls' page events to include try catch.throw after the script = ... But I need these errors to go through the Application_Error to do the logging.What you are doing would result in code like this in the output page:
<script type="text/javascript">
$(document).ready(function(){
<script language='javascript' type='text/javascript'>alert('error')</script>;
});
</script>
which is obviously wrong. You need to change the script variable to:
script = @"alert('error')";
OnError
Exception isn't handled and Render never runs.Because the page isn't erroring and so the OnError event isn't being fired.
Or are you forcing the error and the alert still isn't showing?
By the way, take out the tags in the script insertion, and just have the alert - you already have the defined in your ASPX.
Update:
It's likely to do with the hierarchy of calls, the document.ready() is being called BEFORE the OnError is happening.
Try putting the whole thing into a literal, such as:
<asp:Literal runat="server" ID="JScript" />
protected override void OnError(EventArgs e)
{
JScript.Text = "<script type=\"text/javascript\">alert('error');</script>";
}
throw new ApplicationException()
ApplicationException in Page_Load, how could document.ready be happening before OnError?