Collectives™ on Stack Overflow

Find centralized, trusted content and collaborate around the technologies you use most.

Teams

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

InvalidOperationException while saving a bitmap and using graphics.copyFromScreen parallel-y

I am writing an application to capture the screen using the CopyFromScreen method, and also want to save the image I capture to send over my local network. So, I am trying store the captured screen on one bitmap, and save another bitmap, which is the previously captured screen, on two threads.

However, this is throwing an InvalidOperationException , which says object is currently in use elsewhere. The exception is thrown by System.Drawing.dll.
I have tried locking, and am using separate bitmaps for saving and capturing the screen. How do I stop this from happening? Relevant code:

Bitmap ScreenCapture(Rectangle rctBounds)
    Bitmap resultImage = new Bitmap(rctBounds.Width, rctBounds.Height);
    using (Graphics grImage = Graphics.FromImage(resultImage))
            grImage.CopyFromScreen(rctBounds.Location, Point.Empty, rctBounds.Size);
        catch (System.InvalidOperationException)
            return null;
    return resultImage;
void ImageEncode(Bitmap bmpSharedImage)
    // other encoding tasks
    pictureBox1.Image = bmpSharedImage;
        Bitmap temp = (Bitmap)bmpSharedImage.Clone();
        temp.Save("peace.jpeg");
    catch (System.InvalidOperationException)
        return;
private void button1_Click(object sender, EventArgs e)
    timer1.Interval = 30;
    timer1.Start();
Bitmap newImage = null;
private async void timer1_Tick(object sender, EventArgs e)
    //take new screenshot while encoding the old screenshot 
    Task tskCaptureTask = Task.Run(() =>
            newImage = ScreenCapture(_rctDisplayBounds);
    Task tskEncodeTask = Task.Run(() =>
                    ImageEncode((Bitmap)_bmpThreadSharedImage.Clone());
                catch (InvalidOperationException err)
                    System.Diagnostics.Debug.Write(err.Source);
    await Task.WhenAll(tskCaptureTask, tskEncodeTask);
    _bmpThreadSharedImage = newImage;
                I'm assuming it's _bmpThreadSharedImage which you haven't included in the code above that is causing the problem?
– DavidG
                Jul 27, 2017 at 9:30
                @BugFinder the Exception Unhandled message comes up at Application.Run(new Form1()) line in Program.cs, and the CopyFromScreen and Bitmap.Save methods get highlighted
– Priyank
                Jul 27, 2017 at 9:30
I reproduced your problem in a nutshell by creating a simple winforms project with a single button on it.
public partial class Form1 : Form
    public Form1()
        InitializeComponent();
    private void button1_Click(object sender, EventArgs e)
        Task.Run(() => SomeTask());
    public void SomeTask() //this will result in 'Invalid operation exception.'
        var myhandle = System.Drawing.Graphics.FromHwnd(Handle);
        myhandle.DrawLine(new Pen(Color.Red), 0, 0, 100, 100);
In order to fix this you need to do the following:
public partial class Form1 : Form
    private Thread myUIthred;
    public Form1()
        myUIthred = Thread.CurrentThread;
        InitializeComponent();
    private void button1_Click(object sender, EventArgs e)
        Task.Run(() => SomeTask());
    public void SomeTask() // Works Great.
        if (Thread.CurrentThread != myUIthred) //Tell the UI thread to invoke me if its not him who is running me.
            BeginInvoke(new Action(SomeTask));
            return;
        var myhandle = System.Drawing.Graphics.FromHwnd(Handle);
        myhandle.DrawLine(new Pen(Color.Red), 0, 0, 100, 100);
The issue is (as Spektre implied) a result of trying to call a UI method from a non-UI thread. The 'BeginInvoke' is actually `this.BeginInvoke' and 'this' is the form which was created by the UI thread and therefore all works.
I do not code in C# so I may be wrong here but I assume you are using Windows...
Accessing any visual components (like GDI Bitmap or window ...) is not safe outside WndProc function. So if you are using GDI bitmap (bitmap with device context) or rendering/accessing any visual component from your window inside any thread then there is your problem. After that any call to WinAPI in your app can throw an exception (even unrelated to graphics)
So try to move any such code into your WndProc function. In case you do not have access to it use any event of your window (like OnTimer or OnIdle).
        
Thanks for contributing an answer to Stack Overflow!
Please be sure to answer the question. Provide details and share your research!
But avoid …
Asking for help, clarification, or responding to other answers.
Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.