所以在我XXX.OnPropertyChanged()方法,我有:为什么我有时会在BeginInvoke块中得到NullReferenceException?
public class XXX : IProperyNotifyChanged {
Control itsCtrl;
...
public void Init(Control ctrl) {
itsCtrl = ctrl;
}
public void OnPropertyChanged(string propertyName) {
if (PropertyChanged != null) {
if (itsCtrl.InvokeRequired) {
itsCtrl.BeginInvoke(() => {
PropertyChanged(this, propertyName);
});
} else {
PropertyChanged(this, propertyName);
}
}
}
}
我认为,这将引发以下异常(很少,但现在更经常发生):
System.Reflection.TargetInvocationException was unhandled
HResult=-2146232828
Message=Exception has been thrown by the target of an invocation.
Source=mscorlib
StackTrace:
at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
at System.Delegate.DynamicInvokeImpl(Object[] args)
at System.Windows.Forms.Control.InvokeMarshaledCallbackDo(ThreadMethodEntry tme)
at System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(Object obj)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Windows.Forms.Control.InvokeMarshaledCallback(ThreadMethodEntry tme)
at System.Windows.Forms.Control.InvokeMarshaledCallbacks()
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.Form.WndProc(Message& m)
at DevExpress.XtraEditors.XtraForm.WndProc(Message& msg)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at DevExpress.Utils.Win.Hook.ControlWndHook.CallWindowProc(IntPtr pPrevProc, IntPtr hWnd, Int32 message, IntPtr wParam, IntPtr lParam)
at DevExpress.Utils.Win.Hook.ControlWndHook.WindowProc(IntPtr hWnd, Int32 message, IntPtr wParam, IntPtr lParam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at Client.Program.Main() in C:\Client\Program.cs:line 18
at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
InnerException:
HResult=-2147467261
Message=Object reference not set to an instance of an object.
Source=XXX
StackTrace:
at XXX.<>c__DisplayClass442_0.<OnPropertyChanged>b__0()
InnerException:
我只是在想。发生这种情况是因为在调用BeginInvoke
之前,我没有像this
和propertyName
那样正确复制变量?或者是别的什么?这种情况很少发生,我不知道如何重现它,而且我无法从堆栈跟踪中获得太多东西。你会如何解决这个问题?
是 “itsCtrl” 永远空?在开始调用之前添加一个空检查,看看问题是否消失 – bgura
itsCtrl是MainForm。它永远不可能是空的。 – Denis
@Denis这是不正确的。当表单加载时,它可以是'null'。您遇到竞争状况。 –