为什么CreateWindowEx返回0

Question

VB.NET 2008 Express的

Private Declare Function CreateWindowEx Lib "user32" Alias "CreateWindowExA" (ByVal dwExStyle As Integer, ByVal lpClassName As String, ByVal lpWindowName As String, ByVal dwStyle As Integer, ByVal x As Integer, ByVal y As Integer, ByVal nWidth As Integer, ByVal nHeight As Integer, ByVal hwndParent As Integer, ByVal hMenu As Integer, ByVal hInstance As Integer, ByRef lpParam As Object) As Integer 

Private Const WS_EX_APPWINDOW = &H40000 
Private Const WS_EX_WINDOWEDGE = &H100& 
Private Const WS_SYSMENU = &H80000 
Private Const WS_CAPTION = &HC00000 
Private Const WS_MINIMIZEBOX = &H20000 
Private Const WS_THICKFRAME = &H40000 
Private Const WS_MAXIMIZEBOX = &H10000 
Private Const WS_OVERLAPPEDWINDOW = (WS_OVERLAPPED Or WS_CAPTION Or WS_SYSMENU Or WS_THICKFRAME Or WS_MINIMIZEBOX Or WS_MAXIMIZEBOX) 

Dim AppHandle As Int32 = System.Runtime.InteropServices.Marshal.GetHINSTANCE(System.Reflection.Assembly.GetExecutingAssembly.GetModules()(0)).ToInt32() 

Dim WindowHandle as integer = CreateWindowEx(WS_EX_APPWINDOW Or WS_EX_WINDOWEDGE, "MyWindow", "MyTitle", WS_OVERLAPPEDWINDOW, 0, 0, 640, 480, 0, 0, AppHandle, Nothing) 

CreateWindowEx返回0？

Answer 1

可能的原因是您忘记使用RegisterClass/Ex（）注册“MyWindow”窗口类，未正确设置窗口过程或未正确处理WM_CREATE消息。另外，您的P/Invoke声明是错误的，它不适用于64位操作系统。

不要自己编写这种代码，Windows Forms是CreateWindowEx（）的一个很好的包装。

Answer 2

您需要在调用CreateWindowEx之后检查NULL，如果是，那么您可以立即调用Marshal.GetLastWin32Error，原因为何。