Belfry Images

Today I needed a graphing control, and with a bit of searching found ZedGraph. This has got to be the best open source .NET component I’ve ever used. All you need to do is reference the .DLL, drop a ZedGraph control onto your form or control, and add some code to load in a data range. It’s even easier to make a pie chart and the colours, gradients, etc., are all customisable. Out of the box the control automatically has zooming, scaling, printing and exporting features accessible to the user, and it looks nice and clean. There’s also a ZedGraphWeb control built in which is for use in ASP.NET apps (although I haven’t tried that out).

There are two concurrent versions for both .NET 1.1 and .NET 2 (which is very handy since I’m limited to .NET 1.1 at work). The only difference between the versions is apparently use of templates for collections.

There’s a CodeProject article that gives a pile of simple demo code, and the main site is a Wiki with what looks like plenty of documentation. The library is licensed under the LGPL license, which means that derivative works must be LGPLed, but as long as the library’s DLLs are dynamically linked they can be included in commercial software.

Subversion is my source version control software of choice, but it’s not immediately obvious how to edit the log comment of a past commit (such as after adding a particularly scathing remark that may not be a wise career move). A caveat is that you need to have administrator access to the Subversion repository.

In the repository directory (wherever you created the repository) is a hooks folder (on my system this is H:\IT\svnrepos\pas\hooks). This folder contains scripts that are called by Subversion when various events occur (hooks). The files that are created in a repository’s hooks folder by default are templates of hooks designed for Linux etc. On a Windows server they need to be created as batch files (*.bat) to be executed.

What you need to do is create a hook that will run prior to changing a revision property (such as a log comment) and let Subversion know that changing the comment is permitted. By default changing the log comment is disabled (obviously, or you wouldn’t be reading this). Make a new file in the hooks folder called pre-revprop-change.bat and write the following into it:

if "%4" == "svn:log" exit 0

echo Property '%4' cannot be changed >&2
exit 1

The %4 argument contains which operation is being performed. If the operation is svn:log we indicate success, which is a return code of 0. Otherwise it prints an error and exits with a non-zero, which indicates an error (and that the operation shouldn’t be allowed). Once that is saved, you should be able to use your to Subversion client to edit the comment. Be careful with what you do, as revision properties aren’t versioned, and you won’t be able to undo your changes. You should also probably rename pre-revprop-change.bat to pre-revprop-change.bat.bak once finished.

For reference the logical XOR operator in C# is the same as the bitwise XOR operator: ^. This always gets me because usually the logical boolean operators are like && and || versus the bitwise operators (& and |). I guess it’s the same thing anyway, just a bitwise XOR operation on two booleans. Fascinating.