UI thread crash in WPF when using RTC SDK

[fan-van]

Title:
UI thread crash in WPF after multiple join/leave operations with specific camera

Environment:
Platform: WPF (.NET)
Device: PC with two cameras
SDK: [please fill in RTC SDK name and version]

Steps to Reproduce:

1. Use a device that has two cameras.
2. Start an audio/video call by calling JoinChannel, and specify one of the cameras explicitly.
3. Leave the channel.
4. Repeat step 2 and 3 multiple times (typically 7–8 times).

Actual Result:

• After several join/leave cycles, the WPF application crashes, and the UI thread stops responding.
• Exception details:
  System.InvalidCastException
  HResult=0x80004002
  Message=Unable to cast object of type 'System.__ComObject' to type 'ITfThreadMgr'.

Expected Result:
The application should remain stable even after repeatedly joining and leaving the channel.

Notes:

• The issue only appears when a specific camera is selected.

• If both cameras are available but not explicitly specified, the problem is less frequent.

• Related code excerpt:

  public override int JoinChannel(string? token, string channelId, bool localVideo, bool localAudio)
  {
  
      this.channelId = channelId;
      LogStateChange(prev, _state, "开始加入频道");
  
      try
      {
  
          // Accessing the video device manager and enumerating video devices here
          // causes UI thread issues when called in WPF after multiple join/leave cycles.
  
          var manager = rtc_engine_.GetVideoDeviceManager();
           var list = manager.EnumerateVideoDevices();
  
          if (list.Length > 1)
          {
              var temp = list[1];
              var result = manager.SetDevice(temp.deviceId);
          }
  
          rtc_engine_.EnableVideo();
          rtc_engine_.EnableAudio();
          rtc_engine_.EnableLocalVideo(localVideo);
          rtc_engine_.EnableLocalAudio(localAudio);
  
          rtc_engine_.StartPreview(VIDEO_SOURCE_TYPE.VIDEO_SOURCE_CAMERA_PRIMARY);
  
          ChannelMediaOptions options = new ChannelMediaOptions();
          options.publishCameraTrack.SetValue(localVideo);
          options.publishMicrophoneTrack.SetValue(localAudio);
          options.channelProfile.SetValue(CHANNEL_PROFILE_TYPE.CHANNEL_PROFILE_LIVE_BROADCASTING);
          options.clientRoleType.SetValue(CLIENT_ROLE_TYPE.CLIENT_ROLE_BROADCASTER);
  
          var realChannel = (channelId.Split(';').GetValue(0) ?? string.Empty).ToString();
          var ret = rtc_engine_.JoinChannel(token, realChannel, 0, options);
          this.LogInfo($"JoinChannel Agora 调用 ret={ret}, realChannel={realChannel}");
  
          if (ret != 0)
          {
              _state = EngineState.Initialized;
              return ret;
          }
  
          rtc_engine_.EnableAudioVolumeIndication(300, 3, false);
          return ret;
      }
      catch (Exception ex)
      {
          _state = EngineState.Initialized;
          return -1;
      }
  }