WindowsFormsLifetime

WindowsFormsLifetime

WindowsFormsLifetime.Mvp

A Windows Forms hosting extension for .NET Core's generic host. Enables you to configure the generic host to use the lifetime of Windows Forms. When configured, the generic host will start an IHostedService that runs Windows Forms in a separate thread.

• The Generic Host will use Windows Forms as it's lifetime (when the main form closes, the host shuts down)
• All the benefits of .NET and the Generic Host, dependency injection, configuration, logging...
• Easier multi-threading in Windows Forms

Quick Start

Install the OswaldTechnologies.Extensions.Hosting.WindowsFormsLifetime package from NuGet.

Using Powershell

Install-Package OswaldTechnologies.Extensions.Hosting.WindowsFormsLifetime

Using the .NET CLI

dotnet add package OswaldTechnologies.Extensions.Hosting.WindowsFormsLifetime

Create a new Windows Forms App.

Replace the contents of Program.cs with the following.

namespace WinFormsApp1
{
    internal static class Program
    {
        static void Main()
        {
            CreateHostBuilder().Build().Run();
        }

        public static IHostBuilder CreateHostBuilder() =>
            Host.CreateDefaultBuilder(Array.Empty<string>())
                .UseWindowsFormsLifetime<Form1>()
                .ConfigureServices((hostContext, services) =>
                {

                });
    }
}

Run the app!

Your Windows Forms app is now running on the Generic Host!

Use the Minimal API

Change the projects sdk to Microsoft.NET.Sdk.Web so we can use the WebApplication class.

Add NoDefaultLaunchSettingsFile to the csproj so a launchSettings.json file isn't created automatically for us.

<Project Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup>
    <OutputType>WinExe</OutputType>
    <TargetFramework>net6.0-windows</TargetFramework>
    <Nullable>enable</Nullable>
    <UseWindowsForms>true</UseWindowsForms>
    <ImplicitUsings>enable</ImplicitUsings>
    <NoDefaultLaunchSettingsFile>true</NoDefaultLaunchSettingsFile>
    </PropertyGroup>
</Project>

Replace the contents of Program.cs with the following.

using WinFormsApp1;

var builder = WebApplication.CreateBuilder(args);
builder.Host.UseWindowsFormsLifetime<Form1>();
var app = builder.Build();
app.Run();

Passing options

You can further configure the Windows Forms lifetime by passing Action<WindowsFormsLifeTimeOptions>. For example, with the default options:

using WinFormsApp1;

var builder = WebApplication.CreateBuilder(args);
builder.Host.UseWindowsFormsLifetime<Form1>(options =>
{
    options.HighDpiMode = HighDpiMode.SystemAware;
    options.EnableVisualStyles = true;
    options.CompatibleTextRenderingDefault = false;
    options.SuppressStatusMessages = false;
    options.EnableConsoleShutdown = true;
});
var app = builder.Build();
app.Run();

EnableConsoleShutdown Allows the use of Ctrl+C to shutdown the host while the console is being used.

Instantiating and Showing Forms

Add more forms to the DI container.

using WinFormsApp1;

var builder = WebApplication.CreateBuilder(args);
builder.Host.UseWindowsFormsLifetime<Form1>();
builder.Services.AddTransient<Form2>();
var app = builder.Build();
app.Run();

To get a form use the IFormProvider. The form provider fetches an instance of the form from the DI container on the GUI thread. IFormProvider has one method, GetFormAsync<T> used to fetch a form instance.

In this example, we inject IFormProvider into the main form, and use that to instantiate a new instance of Form, then show the form.

public partial class Form1 : Form
{
    private readonly ILogger<Form1> _logger;
    private readonly IFormProvider _formProvider;

    public Form1(ILogger<Form1> logger, IFormProvider formProvider)
    {
        InitializeComponent();
        _logger = logger;
        _formProvider = formProvider;
    }

    private async void button1_Click(object sender, EventArgs e)
    {
        _logger.LogInformation("Show Form2");
        var form = await _formProvider.GetFormAsync<Form2>();
        form.Show();
    }
}

Invoking on the GUI thread

Sometimes you need to invoke an action on the GUI thread. Say you want to spawn a form from a background service. Use the IGuiContext to invoke actions on the GUI thread.

In this example, a form is fetched and shown, in an action that is invoked on the GUI thread. Then a second form is shown. This example shows how the GUI does not lock up during this process.

public class HostedService1 : BackgroundService
{
    private readonly ILogger _logger;
    private readonly IFormProvider _fp;
    private readonly IGuiContext _guiContext;

    public HostedService1(
        ILogger<HostedService1> logger,
        IFormProvider formProvider,
        IGuiContext guiContext)
    {
        _logger = logger;
        _fp = formProvider;
        _guiContext = guiContext;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        int count = 0;
        while (!stoppingToken.IsCancellationRequested)
        {
            await Task.Delay(5000, stoppingToken);
            if (count < 5)
            {
                await _guiContext.InvokeAsync(async () =>
                {
                    var form = await _fp.GetFormAsync<Form2>();
                    form.Show();
                });
            }
            count++;
            _logger.LogInformation("HostedService1 Tick 1000ms");
        }
    }
}

Model-View-Presenter

The MVP pattern is a good pattern to use to develop a Windows Forms application. The WindowsFormsLifetime.Mvp library contains some extension methods and classes to assist in developing an MVP app with `WindowsFormsLifetime and the generic host.

See the MvpBasicSample sample app

Create a new Windows Forms application. Add a button and label to the form. Edit the form and add a view interface. Hook up some controls to the view interface. In this example, I've hooked up a button click to an EventHandler and a labels value to an int. Let the Form inherit from the view interface.

namespace MvpBasicSample
{
    public interface IMainView
    {
        int Count { get; set; }

        event EventHandler OnIncrementClicked;
    }

    public partial class MainForm : Form, IMainView
    {
        public MainForm()
        {
            InitializeComponent();
        }

        public int Count
        {
            get => Convert.ToInt32(CountLabel.Text);
            set => CountLabel.Text = $"{value}";
        }

        public event EventHandler OnIncrementClicked
        {
            add => IncrementButton.Click += value;
            remove => IncrementButton.Click -= value;
        }
    }
}

Next we create the views presenter. The main forms presenter should inherit from BaseMainFormPresenter. Then we can add the forms logic to the presenter. Initialize the count to 0. Hook up an event handler method to increment the count.

using WindowsFormsLifetime.Mvp;

namespace MvpBasicSample
{
    internal class MainFormPresenter : BaseMainFormPresenter<IMainView>
    {
        public MainFormPresenter(ApplicationContext applicationContext)
            : base(applicationContext)
        {
            View.OnIncrementClicked += OnIncrementClicked;
            View.Count = 0;
        }

        private void OnIncrementClicked(object? sender, EventArgs e)
        {
            View.Count++;
        }
    }
}

With those created, we can update Program.cs. Wipe out what the template created. To use the Minimal API update the sdk in your csproj to Microsoft.NET.Sdk.Web.

using MvpBasicSample;
using WindowsFormsLifetime.Mvp;

var builder = WebApplication.CreateBuilder(args);
builder.Host.UseWindowsFormsLifetime<MainForm, IMainView, MainFormPresenter>();
var app = builder.Build();
app.Run();

Pretty simple!

Only use the Console while debugging

I like to configure my csproj so that the Console runs only while my configuration is set to Debug, and doesn't run when set to Release. Here is an example of how to do this. Setting the OutputType to Exe will run the console, while setting it to WinExe will not.

<PropertyGroup Condition=" '$(Configuration)' == 'Debug' ">
  <OutputType>Exe</OutputType>
</PropertyGroup>

<PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
  <OutputType>WinExe</OutputType>
</PropertyGroup>

Credits

The layout of the WindowsFormsLifetime class is based on .NET Core's ConsoleLifetime.

Stephen's blog post on ExecutionContext vs SynchronizationContext

https://devblogs.microsoft.com/pfxteam/implementing-a-synchronizationcontext-sendasync-method/