记事本字符解码

Question

我正在从program.and打开的记事本中读取文本这是我的代码

const int WM_GETTEXT = 0x000D;
const int WM_GETTEXTLENGTH = 0x000E;

[DllImport("User32.dll", EntryPoint = "SendMessage")]
extern static int SendMessageGetTextLength(IntPtr hWnd, int msg, IntPtr wParam,     IntPtr lParam);
[DllImport("User32.dll", EntryPoint = "SendMessage", CharSet = CharSet.Auto)]
extern static IntPtr SendMessageGetText(IntPtr hWnd, int msg, IntPtr wParam, [Out] StringBuilder lParam);

[DllImport("user32.dll", EntryPoint = "FindWindowEx")]
public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

public static string GetText(IntPtr hwnd)
{
    if (hwnd == IntPtr.Zero)
        throw new ArgumentNullException("hwnd");
    IntPtr handler = FindWindowEx(hwnd, new IntPtr(0), "Edit", null);
    int length = SendMessageGetTextLength(handler, WM_GETTEXTLENGTH, IntPtr.Zero, IntPtr.Zero);
    if (length > 0 && length < int.MaxValue)
    {
        length++;
        StringBuilder sb = new StringBuilder(length);

        SendMessageGetText(handler, WM_GETTEXT, (IntPtr)sb.Length, sb);
        return sb.ToString();
    }
    return String.Empty;
}

它以一种特殊的编码方式获取文本。例如，如果输入的文本是'hello‘，则会得到'興梀㇨ȿڳㇺ’。这个文本的编码是什么，这样我就可以把它解码成ASCII了？

Answer 1

您的问题在于，您实际上是在WM_GETTEXT消息中传递sb.Length，而实际上您应该传递sb.Capacity，甚至只是传递length。

我会这样做：

if (length > 0 && length < int.MaxValue)
{
    StringBuilder sb = new StringBuilder(length+1);
    SendMessageGetText(handler, WM_GETTEXT, (IntPtr)length+1, sb);
    return sb.ToString();
}

我还想指出的是，WM_GETTEXT不会向length < int.MaxValue返回超过64k个字符，这不是您所需要的。

当然，从长远来看，从头到尾使用Unicode可能更好，这样您就可以支持国际文本。

就我个人而言，我总是选择使用Unicode API，并使用以下p/invoke声明：

[DllImport("User32.dll", EntryPoint = "SendMessage", 
    CharSet = CharSet.Unicode, SetLastError = true)]
extern static int SendMessageGetTextLength(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);
[DllImport("User32.dll", EntryPoint = "SendMessage",
    CharSet = CharSet.Unicode, SetLastError = true)]
extern static IntPtr SendMessageGetText(IntPtr hWnd, int msg, IntPtr wParam, StringBuilder lParam);
[DllImport("user32.dll", EntryPoint = "FindWindowEx",
    CharSet = CharSet.Unicode, SetLastError = true)]
public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

Answer 2

既然您是用托管代码编写的，那么您也可以使用托管代码自动化接口，它可以为您完成所有的互操作。为什么要重新发明轮子呢？

using System.Windows.Automation;
public static string GetText(IntPtr hwnd)
{
  IntPtr hwndEdit = FindWindowEx(hwnd, IntPtr.Zero, "Edit", null);
  return (string)AutomationElement.FromHandle(hwndEdit).
     GetCurrentPropertyValue(AutomationElement.NameProperty);
}

您甚至可以让自动化为您执行FindWindowEx：

public static string GetText(IntPtr hwnd)
{
  var editElement = AutomationElement.FromHandle(hwnd).
                    FindFirst(TreeScope.Subtree,
                              new PropertyCondition(
                                     AutomationElement.ClassNameProperty, "Edit"));
  return (string)editElement.GetCurrentPropertyValue(AutomationElement.NameProperty);
}