Question

As the title says, calling Bitmap.GetPixel results in nothing. No value being assigned to the variable, no exceptions being thrown.

Here’s my test code:

private void frmStatTracker_Load(object sender, EventArgs e)
    {
        ScreenCapture sc = new ScreenCapture();
        Color charlie = new Color();
        foreach (Process p in Process.GetProcesses())
        {
            if (p.MainWindowTitle.Contains("DM -"))
            {
                sc.CaptureWindowToFile(p.MainWindowHandle, "C:\\test.png", System.Drawing.Imaging.ImageFormat.Png);
                Image i = sc.CaptureWindow(p.MainWindowHandle);
                Bitmap b = new Bitmap(i);
                pictureBox1.Image = b;

                charlie = b.GetPixel(65, 41);
                return;
            }
        }
    }

When I breakpoint the code, I get the following:

i has a valid image in it from the screenCapture.

b has a valid image in it.

charlie is left with no value. When I add it to the watch list, it tells me that charlie does not exist in the current context, and the variable does not exist in the Locals window. If I breakpoint either the declaration, or the line where it assigns a value, the breakpoint will be hit and appear to be run.

I’m at my wits end, and have no idea how to even start troubleshooting something like this. Help?

Thanks 🙂

Answer 1

You are debugging a release (or other optimized) build. That’s why charlie doesn’t exist. The variable has only been assigned, not otherwise used. The compiler has optimized it away.

EDIT: You can prevent this by using a Debug build, or, as David Heffernan said, by doing something meaningful with charlie.