[Caliburn Micro] How to use the same view for multiple view-models

The default behavior of Caliburn Micro (CM), when it must locate a view from a view-model, is very straightforward: it takes the full name of the view-model, replaces the word "Model" by an empty string, and locates a view with this new name.

One problem with this way is that you must exactly have one view per view-model. So, if you have an abstract view-model, with multiple derived view-models, which only set some filters on the displayed data, you must have one view per derived VM. Which is kind of annoying, useless, and error prone.

In this short article, I'll show you how to easily implement a new feature which will allow us to specify, with an attribute on top of the VM, the view we want CM to display when we activate the VM.

[PostSharp] [FluentValidation] Automatic entity validation with IDataErrorInfo

This post is an english translation of this french post.

One way to manage data validation when using WPF is to implement the interface IDataErrorInfo on the classes to validate, and to modify the XAML file so that WPF automatically uses the functions of this interface to validate the value of the properties (See here for an example).

The problem with this, is that you have to alter your entities to add some logic inside them, which makes them become more than entities. One way to avoid that is provided by FluentValidation, which allows you to deport the validation logic outside of your entities, inside another class, where you can define some validation rules for your entity.

But as we always want our entities to continue to implement IDataErrorInfo, we have to operate a mix with FluentValidation. You can find a way to achieve that in this thread.

This thread was the starting point of the solution I'm going to propose to you, to fix this problematic in an easy way...

[PostSharp] [Caliburn] - Automatically call NotifyOfPropertyChange on the view models

Here, I won't explain what are Caliburn and PostSharp. Their respective documentations, examples and samples already do that very well. But I will show you how to create an aspect which will be applied by PostSharp on the view models of a WPF assembly.

And as a result, on runtime, each time a public property will be changed, the event PropertyChanged of the interface INotifyPropertyChanged will be fired, and the WPF view will be able to refresh its state.

If you already know PostSharp, or have been on their website, you have certainly noticed that they already propose an aspect which intends to implement the interface INotifyPropertyChanged, and to call PropertyChanged when the value of a property is changed.

And if you already know Caliburn, you know that the classes you must inherit from to implement your view models inherit themselves from an abstract class named PropertyChangedBase, which implements INotifyPropertyChanged, and which proposes a function named NotifyOfPropertyChange, to which you give as a parameter the name of the modified property.

The aspect I'm going to show you will allow us to mix these 2 methods.