C# 如何在调用 P/Invoke Sendmessage 时捕获 WIN32 0XFFFF 异常

Question

When I try to use unmanaged code in WPF. eg SendMessage(IntPtr hWnd, int Msg, int wParam, ref TOOLINFO toolInfo), this function may return the 0XFFFF for lpszText in TOOLINFO and application crash directly. I have referred MSDN and found that it is a ERROR_ILLEGAL_CHARACTER error. So I want to ask: How can I catch this kind of error in managed code, or how can I return TOOLINFO a good result.

    struct TOOLINFO
    {
        public int cbSize;
        public int uFlags;
        public IntPtr hwnd;
        public IntPtr uId;
        public RECT rect;
        public IntPtr hinst;
        [MarshalAs(UnmanagedType.LPStr)]
        public string lpszText;
        public IntPtr lParam;
    }

[DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern IntPtr SendMessage(IntPtr hWnd, int Msg, int wParam, ref TOOLINFO toolInfo);

Answer 1

What message are you sending?

Still the solution is easy:

public string lpszText; 

change it to:

public IntPtr lpszText; 

and then marshal the string with Marshal.PtrToStringAuto() (inside a try / catch )

But I see in the description of ToolInfo that YOU have to allocate the buffer. You could try with a StringBuilder() with preallocated length:

public StringBuilder lpszText;

and then BEFORE sending the message

tt.lpszText = new StringBuilder(200);