As .NET developers we have all implemented dictionaries. Often, its a small dictionary with strings or Guids as the key – which is simple and robust. However, sometimes we need to do something a little more ‘serious’ and implement a dictionary that has a complex key consisting of a combination of values. In this case, it is extremely important that the type we use for the key has the following characteristics: Instances of the key’s type must be immutable, as changing their state once they are added to the dictionary will most likely mean that the value they represent cannot be found The key’s type must produce a wide range of hash codes during use, so you’ll need to override the GetHashCode() method, and implement your own algorithm You must override the Equals() method of the key’s type to implement the correct equality algorithm. Also the keys type must implement IEquatable<T> for easy lookups in generic dictionaries. The keys type should ideally be a struct r... [More]

In the MVVM world, things like message boxes (MessageBox.Show) and Dialogs (open file, save file etc), don't naturally fit. These popups are closely tied to the ‘View’ part of MVVM, but they can only really be invoked from the ‘ViewModel’ which will break the clean separation in MVVM. If you google this issue, you will find a wide range of elaborate solutions, many of which are significant engineering projects in their own right. I am a huge fan of implementing simple solutions wherever possible, as verbose code is the number one culprit in un-maintainable projects, so I was keen to find a solution that is simple, robust, elegant and doesnt break the MVVM pattern The solution I came up with, is to use generic Action and Func Delegates. OK, to illustrate my solution, I have created a new project using the ‘WPF Model-View-ViewModel Toolkit’, (http://wpf.codeplex.com/wikipage?title=WPF%20Model-View-ViewModel%20Toolkit), which installs a project template in VS2008 Here is my altered... [More]