I discovered this nasty little problem the other day while building a couple of simple little pages and I thought I should post it so I don’t forget and waste ages on it again!

Essentially the issue is that if you have custom error pages for different types of http status codes such as 401, 403 or 404 then you will have be prepared to do a little bit coding for your 401 page to be displayed unlike your other error pages which you can automatically redirect to by turning on customErrors in the web.config file like so:

<customErrors mode=”Off” defaultRedirect=”Error.htm” >
<error statusCode=”403″ redirect=”AccessDenied.htm”/>
</customErrors>

The problem with 401 is that if you are using the web.config authorisation section as well, and you have explicitly denied the user permission then their request will be authenticated but not authorised and appears to be terminated before the ASP.NET custom error handler can run. For example:

<location path=”MySecurePage.aspx”>
<system.web>
<authorization>
<allow users=”james” />
<deny users=”*” />
</authorization>
</system.web>
</location>

Here the only way to redirect your user to your custom error page will be to check for this condition in the application_end event in the global.asax like so:

protected void Application_EndRequest(Object sender, EventArgs e)
{
if (Response.StatusCode == 401 && Request.IsAuthenticated == true)
{
Response.ClearContent();
Response.Redirect(“AccessDenied.htm”);
}
}

Note: trying to set your custom 401 page in IIS won’t work either as user is authenticated by IIS, but their authorisation fails at the ASP.NET level

Nasty!

Thanks to Ashraf Moollan

I recently discovered Mapack for .NET by Lutz Roeder of Reflector fame. If you haven’t heard of Reflector I don’t know what rock you’ve been hiding under…

Anyway Mapack is a great library of math functions you’re likely to need at some stage but aren’t built into the .Net framework. I was looking for a Matrix class for doing matrix math, and also an example of a least squares implementation in C#. Mapack has both of these and a bunch more.

Check it out at http://www.aisto.com/roeder/dotnet/

Some thing I had always assumed but never bothered to verify is explained here.

Even with all of .NET’s garbage collection trickery, you should still set objects to null as soon as you have finished with them to tell the GC to clean them up at next opportunity.

So I’ve been having this wierd problem with event execution order where half way through handling one event another event handler is fired. If you know why please enlighten me!

Here’s a copy of my newsgroup post which you can find here.

I am seeing some unexpected behaviour in a single threaded winforms app

and was hoping someone could explain what is going on.

I have two events attached to a chart control on my form, and during

execution one event seems to preempt the execution of the other.

My code looks similar to the following:

private void MyChart_Click(object sender, System.EventArgs e)

{

…do some logic tests

GetSomeData();

}

// This event is attached to the context menu for the chart control.

private void DrillDownMenuItem_Click(object sender, System.EventArgs e)

{

…do stuff

}

private DataSet GetSomeData()

{

…setup tasks

…Call web service

…finish stuff

}

What happens is that when I right click and select drill down from the

chart controls context menu the MyChart_Click event fires and does the

logic tests. Execution then steps into the GetSomeData method, but when

the web service is called execution jumps to the

DrillDownMenuItem_Click event. This runs to completion then execution

returns to the GetSomeData method which finishes and finally returns to

the MyChart_Click event handler.

Can someone explain why this is so?

[EDIT] so I figured it out by myself. I turns out it is a bug in the dundas chart control >:-(