Monthly Archives: August 2010

Common sense lost with MVVM

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I am a big fan of using MVVM in WPF applications, but am finding, increasingly,  that even seasoned developers frequently dispose of very good habits, in order to stay true to the pattern.

One such occurrence is is not using message boxes. A  cardinal sin in MVVM, is ensuring that message boxes are never used in View Models. The end result is that one starts to see code like this.

delete

If you don’t have a logging system for your exceptions then you should have, if you do then always ensure that you log the exception. During development, one instinctually starts to determine brittle code, and events where errors can occur and use try-catch blocks. The worst thing you can do here is nothing. It is better not to use the try-catch at all, and just let the application blow-up, because at least you know that there is a problem, and go about fixing it.

I really cannot sufficiently impress upon thee just how much of a bad practice this is, and the amount of time you or other developers that work on your project will spend trying to find obscure bugs that occur because you are swallowing exceptions, just because MVVM stipulates that message boxes should not be used, means they shouldn’t, they should!

Free WPF Ribbon with source code and MVVM samples

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Finally after about 2 years as a CTP, Microsoft have released the WPF ribbon. Due to the delay, one can be certain that they were allowing their third party software vendors as much traction for users that needed a ribbon, but some brilliant open source versions including Fluent Ribbon Control Suite have been developed.

ribbon

The best thing about the release, is that the Office Fluent UI licensing is now no longer a requirement. This allows people to download the software straight away, without having to go through the cumbersome process of logging into the Office website, signing the licensing, then spending half a day trying to locate the installation because it was hidden in a way that made you think they don’t want anyone to use it.

The download for the ribbon is available here. Please ensure that you also take the time to install the source and samples if you want to build MVVM compliant applications with the ribbon (you should be doing this in WPF anyway) . The MSDN documentation is available here.

The installation notes say that this is not supported on XP, but on vista upwards but I have not tested this. If there are issues then you should be able to use another vendor.

After installing the MSI you should have the following template in Visual Studio

project

There is no information on the installation templates for the express editions, but I would hazard a guess as to them never being available, as building applications with a Ribbon is not something a learner ‘typically’ does. If you are using express, then you should be able to add the requisite .dll thus. If you look in my Tree View below in Visual Studio, you will find that there is a reference to RibbonControlsLibrary. This is located at; C:\Program Files (x86)\Microsoft Ribbon for WPF\v3.5.40729.1\RibbonControlsLibrary.dll

tree

Note:  If you installed the source and samples as well, a .zip file with both is available at the same location. Copy this, and unzip it in a location of your choosing

source

The code behind for my window has the following code, so inherit off RibbonWindow

ribboncode

Finally your XAML should be defined so, and you’re good to go!

xaml