Random exceptions when calling UWP APIs on .NET 5

[jkotas]

Original author @a11cf0 . Transferred from dotnet/runtime#46148

Description

I'm trying to call Windows 10 UWP OCR APIs from a .NET 5 Windows Forms application. The code which i'm using was perfectly working on .NET Core 3.1 but on .NET 5 it's extremely unstable. For some reason the code throws either ObjectDisposedException or sometimes InvalidCastException. this usually happens on the call to GetSoftwareBitmapAsync() but sometimes right on the first await. Also, hen wrapped in a method, it usually works on the first run but on subsequent runs it fails as above. Here's a full code sample tested on both .NET Core 3.1 and .NET 5 with the above results.

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Threading.Tasks;

namespace Supergovno
{
    static class Program
    {
        static async Task<int> Main()
        {
            Bitmap Screen = new Bitmap(500, 500);
            Graphics g = Graphics.FromImage(Screen);
            g.CopyFromScreen(1, 1, 00, 0, Screen.Size);
            Bitmap S = new Bitmap(Screen, new Size(500, 500));
            var engine = Windows.Media.Ocr.OcrEngine.TryCreateFromLanguage(new Windows.Globalization.Language("en"));
            using MemoryStream memoryStream = new();
            S.Save(memoryStream, ImageFormat.Bmp);
            var decoder = await Windows.Graphics.Imaging.BitmapDecoder.CreateAsync(memoryStream.AsRandomAccessStream());
            var softwareBitmap = await decoder.GetSoftwareBitmapAsync();
            var ocrResult = await engine.RecognizeAsync(softwareBitmap);
            Console.WriteLine(ocrResult.Text);
            Console.WriteLine("OK!");
            Console.ReadLine();
            return 0;
        }
    }
}

Configuration

I'm using .NET 5.0.101 on Windows 10 X64 10.0.19042.

Regression?

Yes. Everything is working on .NET Core 3.1.

Other information

[manodasanW]

ObjectDisposed exception is probably a dupe of #584. @a11cf0 Can you provide the exception message or stack when you got the InvalidCastException,

[a11cf0]

ObjectDisposed exception is probably a dupe of #584. @a11cf0 Can you provide the exception message or stack when you got the InvalidCastException,

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
---> System.InvalidCastException: Specified cast is not valid.
at MagicKeys.MagicKeys.OCR(Int32 W, Int32 H, Int32 X, Int32 Y, Int32 Zoom) in D:\Root\src\MagicKeys\MagicKeys\Core\ImgManager\ImgToText.cs:line 42
at MagicKeys.MagicKeys.<>c__DisplayClass63_0.<b__0>d.MoveNext() in D:\Root\src\MagicKeys\MagicKeys\Core\ImgManager\ImgToText.cs:line 22
--- End of stack trace from previous location ---
at MagicKeys.MagicKeys.ImgToText(Int32 W, Int32 H, Int32 X, Int32 Y, Int32 Zoom) in D:\Root\src\MagicKeys\MagicKeys\Core\ImgManager\ImgToText.cs:line 22
at MagicKeys.MagicKeys.VUFOCR(String Param) in D:\Root\src\MagicKeys\MagicKeys\Core\VUFManager\VUFOCR.cs:line 11
--- End of inner exception stack trace ---
at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)
at MagicKeys.MagicKeys.InvokeFromString(String InvokeFunc, String FuncParam) in D:\Root\src\MagicKeys\MagicKeys\Core\Common\InvokeFromString.cs:line 33

[a11cf0]

I see that #584 has been fixet. Is it possible to somehow apply this fix without switching to experimental .NET revisions or waiting for .NET 6?

[manodasanW]

@a11cf0 , typically once we check in a fix, it will be shipped as part of the next CsWinRT update which will then be used to generate the Windows SDK projection packages and shipped in a .NET 5 update. So your probably won't need to wait till .NET 6 unless the fix is considered a breaking change.

But it looks like I am still able to hit the ObjectDisposed exception in your repro even with the fix from the bug I mentioned. We will need to investigate further, but your repro is helpful.

[huoyaoyuan]

My call stack is different, but it's an ObjectDisposed when accessing ImageSource.SetSourceAsync. Maybe related.

[huoyaoyuan]

I can still hit a random ObjectDisposedException after updating to .NET SDK 5.0.102

[huoyaoyuan]

@manodasanW I've tried your fix (copying WinRT.Runtime.dll from latest master), but my app is still crashing.

Yes confirmed. My issue is still present.

Since the exception shows as a native exception and can't be caught at managed side, I think it's probably a WinUI issue instead.

[a11cf0]

On .NET 5.0.103 with almost the same test code I no longer get the ObjectDisposedException but the InvalidCastException is now extremely frequent. Previously it was quite rare.

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> System.InvalidCastException: Unable to cast object of type 'Windows.Foundation.AsyncOperationWithProgressCompletedHandler`2[Windows.Storage.Streams.IBuffer,System.UInt32]' to type 'Windows.Foundation.IAsyncOperation`1[Windows.Graphics.Imaging.BitmapDecoder]'.
   at MagicKeys.MagicKeys.ImgToText(Int32 W, Int32 H, Int32 X, Int32 Y, Int32 Zoom) in D:\Root\src\MagicKeys\MagicKeys\Core\ImgManager\ImgToText.cs:line 27
   at MagicKeys.MagicKeys.VUFOCR(String Param) in D:\Root\src\MagicKeys\MagicKeys\Core\VUFManager\VUFOCR.cs:line 11
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)
   at MagicKeys.MagicKeys.InvokeFromString(String InvokeFunc, String FuncParam) in D:\Root\src\MagicKeys\MagicKeys\Core\Common\InvokeFromString.cs:line 33

[manodasanW]

@a11cf0 Are you running into the InvalidCastException with the above repro code that you had posted?

[a11cf0]

@a11cf0 Are you running into the InvalidCastException with the above repro code that you had posted?

No, but the main part is the same. Here's a complete code sample that throws the exception. I added the loop, because the InvalidCastException is never thrown on the first run.

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace govno
{
    static class Program
    {
        static async Task Main()
        {
            for (int i = 0; i < 10; i++)
            {
                Bitmap Screen = new Bitmap(500, 500);
                Graphics g = Graphics.FromImage(Screen);
                g.CopyFromScreen(1, 1, 00, 0, Screen.Size);
                Bitmap S = new Bitmap(Screen, new Size(500, 500));
                var engine = Windows.Media.Ocr.OcrEngine.TryCreateFromLanguage(new Windows.Globalization.Language("en"));
                using MemoryStream memoryStream = new();
                S.Save(memoryStream, ImageFormat.Bmp);
                var decoder = await Windows.Graphics.Imaging.BitmapDecoder.CreateAsync(memoryStream.AsRandomAccessStream());
                var softwareBitmap = await decoder.GetSoftwareBitmapAsync();
                var ocrResult = await engine.RecognizeAsync(softwareBitmap);
                MessageBox.Show(ocrResult.Text, "Result");
            }
        }
    }
}

[manodasanW]

Remaining issue mentioned here is tracked by #762