Caliburn.Micro Notify Change for Static Property

Normally in Caliburn.Micro and MVVM in general, you would have non-static properties that would be updated and notified like this:

private string _name;

public string Name
{
    get { return _name; }
    set
    {
        _name = value;
        NotifyOfPropertyChange(() => Name);
    }
}

However, if I had a static property, for example, if I wanted a property that could be accessed by another namespace, I would need to implement my own event handler as the default NotifyOfPropertyChange doesn’t operate on static properties.

This is the new EventHandler that I implemented:

public static event EventHandler<PropertyChangedEventArgs> StaticPropertyChanged;
private static void NotifyStaticPropertyChanged(string propertyName)
{
    StaticPropertyChanged?.Invoke(null, new PropertyChangedEventArgs(propertyName));
}

Finally, in order to use it. I would use this instead of the first example for non-static properties:

private string _name;

public string Name
{
    get { return _name; }
    set
    {
        _name = value;
        NotifyStaticPropertyChanged(() => Name);
    }
}

I hope this helps someone. Enjoy!

Caliburn.Micro MVVM Boolean To Visibility Converter

Say I wanted to toggle the visibility of a WPF object in an MVVM way, what would I need to do?

Here is what I currently have:

  • ViewModels
    • ShellViewModel
    • LoadingViewModel
  • Views
    • ShellView
    • LoadingView

When the application is loaded, the ShellViewModel is used to display the LoadingView in a ContentControl object. I have a button on there that I want to become visible after the LoadingView has been activated for 5 seconds.

What I need to do is created a custom class that has two methods: a way of converting a boolean to a visibility; and a way of converting a visibility to a visibility.

So I created a new folder in my tree called “Converters“. In here, I create a new class called “BooleanToVisiblityConverter“.  Here is what my tree now looks like:

  • ViewModels
    • ShellViewModel
    • LoadingViewModel
  • Views
    • ShellView
    • LoadingView
  • Converters
    • BooleanToVisibilityConverter

In my BooleanToVisibilityConverter class, I inherited from IValueConverter and added the necessary two methods. You can see the entire class below:

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Data;

namespace Project.Converters
{
    /// <summary>
    /// Contains the converter and convertback methods for the boolean to visibility conversions
    /// </summary>
    public sealed class BooleanToVisibilityConverter : IValueConverter
    {
        /// <summary>
        /// Used to convert a boolean to a visibility
        /// </summary>
        /// <param name="value">This is the boolean input</param>
        /// <param name="targetType"></param>
        /// <param name="parameter"></param>
        /// <param name="culture"></param>
        /// <returns>Returns a visibility</returns>
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            if (!(value is bool))
            {
                //If there is an issue with the input, return collapsed
                return Visibility.Collapsed;
            }
            return (bool)value ? Visibility.Visible : Visibility.Collapsed;
        }

        /// <summary>
        /// Used to take a visibility and returns a visibility
        /// </summary>
        /// <param name="value">This is the boolean input</param>
        /// <param name="targetType"></param>
        /// <param name="parameter"></param>
        /// <param name="culture"></param>
        /// <returns>Returns a visibility</returns>
        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            if (!(value is Visibility))
            {
                //If there is an issue wtih the input, return collapsed
                return Visibility.Collapsed;
            }
            return (Visibility)value == Visibility.Visible;
        }
    }
}

Next, in my LoadingView, I added “ xmlns:sp=”clr-namespace:Project.Converters” so that the view could use the converter namespace. This is what my view dependancies look like:

<UserControl x:Class="Project.Views.MainView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:cal="http://www.caliburnproject.org"
             xmlns:sp="clr-namespace:Project.Converters"
             xmlns:local="clr-namespace:Project.Views"
             mc:Ignorable="d" FontSize="14" FontFamily="/Project;component/Assets/Fonts/#Roboto"
             d:DesignHeight="550" d:DesignWidth="400">

I then added the binding to the visibility property of my button. You can see this below:

<Button Name="LoadingButton" Content="Press Me" Visibility="{Binding ButtonIsVisible, Converter={StaticResource BooleanConverter}, FallBackValue=Collapsed}"

This means that it will get its visibility value from the LoadingViewModel and if this fails, it will fall back to being collapsed.

We’re almost done. In the LoadingViewModel create a full property which will hold and change the value for the visibility. This needs to be named the same as the binding given in the LoadingView (i.e ButtonVisibility). You can see this below:

private bool _buttonIsVisible;

public bool ButtonIsVisible
{
    get {return _buttonIsVisible;
    set
    {
        if (value != _buttonIsVisible)
        {
            _buttonIsVisible = value;
            NotifyOfPropertyChange(() => ButtonIsVisible);
        }
    }
}

So now if you want the button to be visible, you can just update the ButtonIsVisible property in the LoadingViewModel. Here is an example below (Don’t actually do this):

public LoadingViewModel(){
    ButtonIsVisible = false;
    Task.Delay(5000);
    ButtonIsVisible = true;
}

I hope this helped you. Enjoy!

Setting Up Caliburn.Micro MVVM

This is a fairly lengthy post that shows how to set up an initial MVVM WPF form using Caliburn.Micro.

Let’s get started, we’ll open up Visual Studio and chose to create a new WPF:

Visual Studio -> New Project -> WPF App (.Net Framework)

I usually set the project name to something like WPFUI and my solution name to be something like MVVMProject or the actual product name. For example, Microsoft might use Microsoft Outlook. Probably not, but you get what I’m saying…

 

1)

First I will add Caliburn.Micro to my project. To do this go to Solution Explorer -> References -> Add NuGet Packages and search for Caliburn.Micro:

 

2)

Now we can delete the MainWindow.xaml

 

3)

Create a Views and ViewModels folder. This is where your viewmodels and views will call home.

 

4)

Create a new class in the ViewModels folder and call it ShellViewModel and make it public. You’ll also want to inherit from screen and add the using statement for Caliburn.Micro:

5)

Create a new window in the Views folder and call it ShellView

6)

Create a new class in the root directory called Bootstrapper and inherit from BootstrapperBase and add the using statement for Caliburn.Micro

7)

In App.xaml remove the StartupUri element and add the bootstrapper class as a resource by adding:

<ResourceDictionary>
    <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary>
            <local:Bootstrapper x:Key="Bootstrapper" />
        </ResourceDictionary>
    </ResourceDictionary.MergedDictionaries>
</ResourceDictionary>

Your app.xaml should look like this:

 

8)

Now go back into your Bootstrapper class and add the following:

public Bootstrapper()
{
    Initialize();
}
protected override void OnStartup(object sender, StartupEventArgs e)
{
    DisplayRootViewFor<ShellViewModel>();
}

You’ll also need to add a using statement for System.Windows and ProjectName.ViewModels.

The program should now launch and show an empty white screen with “ShellView” as the window’s title. This is the first entry into a hopefully long series into the world of Caliburn.Micro.

Enjoy! 😊