WindowPhone 7.x|如何在应用程序进入后台时正确关闭/暂停视频录制

当我在视频录制过程中锁定手机时，我的应用程序挂起了堆栈跟踪，如下所示：

System.Windows.dll！MS.Internal.NativePhotoMethods.CapMan_Disconnect（int dwSeq）
System.Windows.dll！System.Windows.Media.CaptureSource.CaptureThread（）+0x2dd字节mscorlib.dll！System.Threading.ThreadHelper.ThreadStartHelper（System.Threading.ThreadHelper t）+0x1d字节
mscorlib.dll！System.Threading.ThreadHelper.ThreadStart_Context（对象状态）+0xb字节
mscorlib.dll！System.Threading.ExecutionContext.Run（System.Threading.ExecutionContext ExecutionContext，System.Threading.Context回调，对象状态）+0x63字节
mscorlib.dll！System.Threading.ThreadHelper.ThreadStartHelper（）+0x2a字节

当我调用captureSource.Stop()（锁定事件PhoneApplicationFrame.Obscure）时，我的应用程序挂起了不同的堆栈跟踪：

mscorlib.dll！System.Threading.Thread.Join（）System.Windows.dll！System.Windows.Media.CaptureSource.StopManagedImageCapture（）+0x3e字节
System.Windows.dll！System.Windows.Media.CaptureSource.Stop（）+0x10字节
HelloWorld.dll！HelloWorld.App.RootFrame_Obscured（对象发送器，Microsoft.Phone.Controls.ObscuredEventArgs e）第96行+0xa字节C#Microsoft.Phone.dll！System.Windows.Controls.Frame.FireEventHandler（System.EventHandler处理程序，对象发送器，Microsoft.Phone.Controls.ObscuredEventArgs参数）+0xd字节Microsoft.Phone.dll！Microsoft.Phone.Controls.PhoneApplicationFrame.ShellPageManager_OnLockStateChange（对象发送方，Microsoft.Phone.Shell.Interop.LockStateChangeEventArgs args）+0x48字节
Microsoft.Phone.Interop.dll！Microsoft.Phone.Shell.Interop.ShellPageManager.ShellPageCallback_OnLockStateChange（对象源，Microsoft.Phone.Shell。Interop.LockStateChangeEventArgs e）+0x12字节
Microsoft.Phone.Interop.dll！Microsoft.Phone.Shell.Interop.ShellPageCallback.FireOnLockStateChange（bool fLocked）+0x41字节
【外部代码】

如何防止挂起并正确暂停/关闭CaptureSource？