Mathias Brandewinder on .NET, F#, VSTO and Excel development, and quantitative analysis / machine learning.
30. May 2010 11:01

Silence is gold. Or… is it? You may have noticed that VSTO swallows exceptions; that is, if something goes wrong in your add-in code, Office will discreetly carry on as if nothing had happened. Consider the following code:

public partial class ThisAddIn
{
private int counter;

private void ThisAddIn_Startup(object sender, System.EventArgs e)
{
this.Application.SheetActivate += SheetActivated;
}

private void SheetActivated(object sheet)
{
MessageBox.Show("Counter = " + this.counter.ToString());
throw new ArgumentException("Something went south here.");
counter++;
}

The add-in is supposed to maintain a counter of how many times the user has changed the activate sheet. However, a bug throws an exception right before the counter is updated. If you run this code, you’ll see that the MessageBox keeps being displayed every time you change the selected worksheet, but the counter stays firmly at zero, and never gets updated.

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28. May 2010 08:29

Via the INFORMS newsletter, I found out this cool competition (trains and analytics, how much cooler can it get?): can you find the best plan to refuel the locomotives of a railroad company?

Create a cost-effective plan to fuel the locomotives that power a railroad's trains. Specify how many fuel trucks to contract at each yard and how much fuel to dispense into the locomotives of trains that run over a specified time horizon. Ensure that no locomotive runs out of fuel en route between yards. Sounds easy? We'll see about that!

Learn more about the challenge at the competition website, and register by June 15, for glory, bragging rights, a shot at a first prize of \$2,500 – and help spare some poor chaps an unpleasant day:

26. May 2010 06:55

I finally got to reviewing and scrubbing the code for the part 2 of my Excel 2007 VSTO tutorial; you can download the code here. Next chapter, we will venture into the joys of deployment.

In the meanwhile, please feel free to let me know in the comments what you think, like and dislike, and how I can make this better!

20. May 2010 06:43

I gave a quick Firestarter talk at the San Francisco .Net user group yesterday about .less. .less (‘dot-less’) is an open source .Net library, which extends the functionality of CSS (it works with your existing CSS files), adding features like variables, using a syntax close to CSS. If you find that working with CSS causes some teeth-grinding , you should probably have a look!

16. May 2010 08:14

I have been working with trees quite a bit lately, because I am coding something which involves probability trees: based on the state of the system, there is a number of things which can happen, each with a certain probability.

I ended up writing a simple generic Node class, which can contain anything, and can have multiple children, along these lines:

public class Node<T>
{
public Node()
{
this.Children = new List<Node<T>>();
}

public T Content
{
get;
set;
}

public List<Node<T>> Children
{
get;
private set;
}

public bool IsLeaf
{
get
{
return (this.Children.Count() == 0);
}
}
}

Pretty quickly, I realized I would need to get the list of all nodes under a certain node, as well as the list of its leaves (a leaf being a node that has no children, i.e. an endpoint of the tree). This is a job tailor-made for recursion: if a node is a leaf, return it, otherwise, search further in all his children.

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