Is there a method to check if a background image is loaded completely in a C# form?

Question

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How to fix the flickering in User controls

I am currently working on a program that dynamically loads in an Image for the Background image of the form. I want the form to be visible as soon as the image is fully applied to the background.

I've tried the form event BackgroundImageChanged but this didn't work.

If the image is high resolution I can see the form showing up and the image is still building up itself.

The code snippet:

this.backgroundImage = loadedImage;
// Thread.Sleep(5000);
this.Show();

As you can see I am using Thread.Sleep() to win some time to fully load the image before showing the form. but is there a way like this :

this.backgroundImage = loadedImage;
while( imageIsNotFullyLoaded() ) { }
this.Show();

Or is there any other method or an event that I haven't seen yet?

EDIT:

my code:

forn1.cs :

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;

namespace GameClient {
    public partial class FormMain:Form {
        getImage _getImage;
        public FormMain() {
            InitializeComponent();
        }

        private void FormMain_Load( object sender, EventArgs e ) {
            _getImage = new getImage();
            Image  splashLogo = _getImage.fromURL( "http://ace-acid.no-ip.org/GameClient/splash.png" );
            this.BackgroundImage = splashLogo;
            Thread.Sleep(3000);
            this.Show();
        }

        private void btnLogin_Click( object sender, EventArgs e ) {

            this.Hide();
        }
    }
}

getImage.cs :

using System;
using System.Drawing;
using System.IO;
using System.Net;

namespace GameClient {
    class getImage {
        public Image fromURL( string URL ) {
            Image tmpImg = null;
            try {
                HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create( URL );
                request.AllowWriteStreamBuffering = true;
                request.Timeout = 20000;
                WebResponse response = request.GetResponse();
                Stream stream = response.GetResponseStream();
                tmpImg = Image.FromStream( stream );
                response.Close();
            } catch( Exception ex) {
                return null;
            }
            return tmpImg;
        }
    }
}

You probably should stop posting questions from your cell phone; there were too many grammatical errors in your original post. — Robert Harvey, Oct 29 '12 at 20:55
I've tried answering questions on my cell. It's a nightmare and usually ends up with me telling someone: "to bind your data, call yourGrid.Daniel() (or the like)" due to the amazing auto-correct. — Yatrix, Oct 29 '12 at 20:58
are you viewing the application on the actual desktop or via remote desktop? I've seen it happen on remote desktop that a lag occus with a background image on a WinForms windows application — Aaron Anodide, Oct 29 '12 at 20:59
btw: i'm german and my english is not the best , sorry for that. — Ace, Oct 29 '12 at 21:19
@JohnSaunders I see `using System.Windows.Forms;` in the code — L.B, Oct 29 '12 at 22:08
@L.B. I thought it would be nice if the OP told us instead of requiring us to read his code. — John Saunders, Oct 29 '12 at 23:39

score 0 · Answer 1 · answered Oct 29 '12 at 21:45

0

There isn't a way to do it like that. The form's actual invalidation/painting is carried out by an interop call to unmanaged code, and there's no callback or hook for when it's finished. You'll have to live with your current procedure.

If you want it to be at least non-blocking, then depending on your .NET target you can use await Task.Delay(5000) (or something equivalent).

answered Oct 29 '12 at 21:45

Jeff

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what is the diference to Thread.Sleep(); ? – Ace Oct 29 '12 at 21:49
`Thread.Sleep()` will block (literally suspend) the calling thread, while `await Task.Delay()` won't block your UI thread. See [here](http://msdn.microsoft.com/en-us/library/vstudio/hh191443.aspx) for more info on `async`/`await`. – Jeff Oct 29 '12 at 21:52
Also I don't think waiting an *unknown* amount of time (`Task.Delay(5000)`) is a good idea – L.B Oct 29 '12 at 21:52
5000 isn't unknown, it's arbitrary. I don't think it's a good idea either, but in lieu of a proper callback... – Jeff Oct 29 '12 at 21:55

score 0 · Answer 2 · answered Oct 29 '12 at 21:55

You can do a simple thing like invoking a delegate, if the method called by a delegate has a return value, the thread will wait for it to finish, so you can try this code:

        delegate Image getImageDelegate(string url);
        private void Form1_Load(object sender, EventArgs e)
        {
            _getImage = new getImage();
Image splashLogo = (Image)this.Invoke(new getImageDelegate(_getImage.fromURL), new object[] { "http://ace-acid.no-ip.org/GameClient/splash.png" });
            this.BackgroundImage = splashLogo;
            this.Show();

        }

Is there a method to check if a background image is loaded completely in a C# form?

2 Answers2