OswaldTechnologies.Extensions.Hosting.WindowsFormsLifetime 0.1.0

OswaldTechnologies.Extensions.Hosting.WindowsFormsLifetime

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.

Getting Started

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

Setup the Program class

When creating a new Windows Forms .NET Core project your Program class will look like the following:

static class Program
{
    /// <summary>
    ///  The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main()
    {
        Application.SetHighDpiMode(HighDpiMode.SystemAware);
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new Form1());
    }
}

We will transform this to look very similar to an ASP.NET Core Web Application's Program class. We then chain the UseWindowsFormsLifeTime<TStartForm> extension method onto the IHostBuilder. Replace TStartForm with your startup Form. The below is an example of an updated Program class using the default builder.

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

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

If you choose not to use the default builder, here is an example with only the Windows Forms lifetime configured.

static class Program
{
    static void Main()
    {
        new HostBuilder().UseWindowsFormsLifetime<Form1>().Build().Run();
    }
}

Passing options

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

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

    public static IHostBuilder CreateHostBuilder() =>
        Host.CreateDefaultBuilder(Array.Empty<string>())
            .UseWindowsFormsLifetime<Form1>(options =>
            {
                options.HighDpiMode = HighDpiMode.SystemAware;
                options.EnableVisualStyles = true;
                options.CompatibleTextRenderingDefault = false;
                options.SuppressStatusMessages = false;
                options.EnableConsoleShutdown = true;
            })
            .ConfigureServices((hostContext, services) =>
            {
                    
            });
}

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.

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");
        }
    }
}

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