mediaCapture.CameraStreamState occasionally throws InvalidCastException

Hong 1,051

mediaCapture.CameraStreamState usually works fine, but occasionally it throws the following:

Exception: Unable to cast object of type 'EETypeRva:0x0006C288(Windows.Media.Capture.MediaCapture)' to type 'EETypeRva:0x0006C338'.
Type: System.InvalidCastException
Stack trace:
at System.Runtime.InteropServices.McgMarshal.GetInterface(__ComObject, RuntimeTypeHandle) + 0x112
at __Interop.ComCallHelpers.Call(__ComObject, RuntimeTypeHandle, Int32, Void*) + 0x3a
at __Interop.ForwardComStubs.Stub_63TThis + 0x31
at Windows.Media.Capture.MediaCapture.get_CameraStreamState() + 0x18

Could anyone shed some light on the possible causes?

Roy Li - MSFT 32,051 Reputation points Microsoft Vendor

2021-06-09T03:03:58.443+00:00

Based on the error message, it's an issue that happens when the mediaCapture is getting an unexpected type. Could you reproduce this issue? If not, it will be hard to locate the issue. My suggestion is that try to check the type first before you use it.
Hong 1,051 Reputation points

2021-06-09T03:49:04.633+00:00

I cannot reproduce it. I is reported in analytics.
Could you tell me which type I should check?
Roy Li - MSFT 32,051 Reputation points Microsoft Vendor

2021-06-09T05:58:00.587+00:00

This depends on the code you are using, Just check if the parameter or the result is the expected type after you get it and before you use it.
Hong 1,051 Reputation points

2021-06-09T10:50:30.58+00:00
I should have included the actual code in my original question. Here it is:

if (_mediaCapture != null && _mediaCapture.CameraStreamState == CameraStreamState.Streaming) { //do something }
Roy Li - MSFT 32,051 Reputation points Microsoft Vendor

2021-06-10T06:46:28.31+00:00

So the exception comes from this line of code, right?
Hong 1,051 Reputation points

2021-06-10T11:31:29.7+00:00

Yes, it comes from "_mediaCapture.CameraStreamState == CameraStreamState.Streaming". I believe the property CameraStreamState throws the exception.
Roy Li - MSFT 32,051 Reputation points Microsoft Vendor

2021-06-11T09:59:29.07+00:00

Well, it's an interesting behavior. I'd suggest you use a variable to get the _mediaCapture.CameraStreamState first. Then use the try/catch block to handle the possible exception that comes from that property. This might be helpful to avoid the app's crash.
Hong 1,051 Reputation points

2021-06-11T12:47:14.837+00:00

Sorry for the confusion. I did not include all the code. "if (_mediaCapture != null && _mediaCapture.CameraStreamState == CameraStreamState.Streaming)" is in a try-catch block. The exception is logged in app analytics. It has taken multiple attempts to narrow the origin to that statement.
Roy Li - MSFT 32,051 Reputation points Microsoft Vendor

2021-06-14T09:10:02.963+00:00

It is hard to locate this issue if you could not reproduce this issue. If you are able to collect the dump or log file of this issue. I'd suggest you open a support ticket for this. Please contact our paid phone support at MS Support. You will get 1:1 support on that. Please kindly note that your support ticket will be free if it is Microsoft's issue.