Crash 'Unable to cast object of type 'System.__ComObject' to type 'ITfThreadMgr'.'

• .NET Core Version: 3.1
• Windows version: (Windows 10 Pro 19043.1645)
• Does the bug reproduce also in WPF for .NET Framework 4.8?: Unknow
• Is this bug related specifically to tooling in Visual Studio (e.g. XAML Designer, Code editing, etc…)? No.
• Security issues and bugs should be reported privately, learn more via our responsible disclosure guidelines.

Problem description: Unknown cause. 1.We used WebView2 (1.3.153.51) in our project, We are using WebView2 when the crash happens. I’m not sure if it has anything to do with this. 2.Is it possible that the problem is caused by the Chinese input ?

Actual behavior:

App crash at Dispatcher.GetMessagePump()

It looks like the ‘threadManager’ value is of the wrong type?

Expected behavior:

Minimal repro:

[ThomasGoulet73]

According to the Windows SDK, ITfThreadMgr2 does not implement ITfThreadMgr (They do not share the same vtbl). It seems that even though ITfThreadMgr2 does not implement ITfThreadMgr, you can call QueryInterface with ITfThreadMgr2 on a ITfThreadMgr pointer. So if the pointer returned by TF_CreateThreadMgr is ITfThreadMgr2 it could cause this type of exception. I don’t know if this is the case here because it would be very weird since TF_CreateThreadMgr returns ITfThreadMgr according to the SDK. I’m not setup to try it since it looks like it requires specific input but if anyone can try to cast everything to ITfThreadMgr2 before using the instance of the COM object it would be great.

[jim-jiang-github]

@jim-jiang-github Do you mean call the CoInitialize twice without call the UnCoInitialize?

Yes. Alternatively, you can reproduce this issue by making multiple calls to CoInitialize in the code.