Shows how to use Eto.Forms with async/await and background tasks to perform long running work while keeping the UI responsive.

RunEtoWithBackgroundTasks.cs

using System;
using Eto.Forms;
using System.Threading;
using System.Threading.Tasks;
using System.Collections.Generic;
using Eto.Drawing;

namespace RunEtoWithBackgroundTasks
{

	class ProgressForm : Form
	{
		ProgressBar progressBar;

		public float Progress { 
			get { return progressBar.Value / 1000f; }
			set { progressBar.Value = (int)Math.Round (Math.Min (value, 1f) * 1000f); } 
		}

		public ProgressForm ()
		{
			Title = "Progress!";
			progressBar = new ProgressBar { MaxValue = 1000, Width = 200 };
			Content = progressBar;
		}
	}

	class ImageForm : Form
	{
		ImageView imageView;

		public Image Image { get { return imageView.Image; } set { imageView.Image = value; } }

		public ImageForm ()
		{
			Title = "Image!";
			imageView = new ImageView { Size = new Size (200, 200) };
			Content = imageView;
		}
	}

	static class UI
	{
		static Dictionary<string, Form> forms = new Dictionary<string, Form> ();

		static T CreateForm<T> (string name)
			where T: Form, new()
		{
			Form form;
			if (!forms.TryGetValue (name, out form)) {
				form = new T ();
				forms.Add (name, form);
				form.Show ();
			}
			;
			return (T)form;
		}

		static T GetForm<T> (string name)
			where T: Form
		{
			Form form;
			if (forms.TryGetValue (name, out form))
				return (T)form;
			return null;
		}

		public static void CloseWindow (string name)
		{
			Form form;
			if (forms.TryGetValue (name, out form)) {
				form.Close ();
				forms.Remove (name);
			}
		}

		public static void ShowProgress (string name, float progress)
		{
			var form = CreateForm<ProgressForm> (name);
			form.Progress = progress;
		}

		public static void ShowImage (string name, Image image)
		{
			var form = CreateForm<ImageForm> (name);
			form.Image = image;
		}
	}


	public class Program
	{
		[STAThread]
		public static void Main (string[] args)
		{
			var app = new Application ();
			// app.Invoke shouldn't be required here, but it is as of Eto 2.1
			app.Initialized += (sender, e) => app.Invoke (async () => {
				for (int i = 0; i < 1000; i++) {
					//process an i-th image
					await Task.Run (() => {
						// do actual background work here
						Thread.Sleep (1); // simulate work
					});
					UI.ShowProgress ("progress1", (float)i / 1000); //(create a form if not already shown and set the progress)
				}

				UI.CloseWindow ("progress1");

				for (int i = 0; i < 1000; i++) {
					//take the-ith image
					await Task.Run (() => {
						// do actual background work here
						Thread.Sleep (1); // simulate work
					});
					var img = new Bitmap (200, 200, PixelFormat.Format32bppRgb);
					using (var g = new Graphics (img)) {
						g.DrawText (SystemFonts.Default (), Brushes.White, 0, 0, "Image " + i);
					}
					UI.ShowImage ("imageWnd", img); //(create a form if not already shown and set the image)
				}

				UI.CloseWindow ("imageWnd");

				app.Quit ();
			});
			app.Run ();
		}
	}
}