以下是我目前对您的问题的猜测：
- HWND_PRINTER_NAME 不是 1
- 您要查找的类名不是“ComboBox”
- 未列出代码中的问题：
- SendMessageW DllImport 错误，或参数处理不当
您在列出的代码中确实存在一些错误，因此我的代码并不完全相同，但这是我用来尝试解决您的问题的代码。我无法让它表现得像你描述的那样。我的代码根本找不到类名称为“ComboBox”的子窗口。
using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Text;
namespace PrinterChoosenInAcrobat
{
class Program
{
public const uint WM_GETTEXTLENGTH = 0x000E;
private const uint WM_GETTEXT = 0x000D;
// External OS calls
[DllImport("user32.dll", EntryPoint = "SendMessage", CharSet = CharSet.Auto)]
public static extern bool SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam,
StringBuilder lParam);
[DllImport("user32.dll", SetLastError = true)]
public static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wparam,
IntPtr lparam);
[DllImport("User32.dll")]
public static extern Int32 FindWindow(String lpClassName, String lpWindowName);
[DllImport("user32.dll")]
static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName,
int nMaxCount);
static void Main(string[] args)
{
try
{
IntPtr windowHandle = (IntPtr)FindWindow("AcrobatSDIWindow", null);
string text = GetWindowText(windowHandle);
Console.WriteLine(text);
}
catch (Exception ex)
{
Console.Out.WriteLine(ex.Message);
}
// Don't close before I get to read the results
Console.WriteLine();
Console.WriteLine("Press Enter to quit.");
Console.ReadLine();
}
static string GetWindowText(IntPtr hwnd_printDialog_in_Acrobat)
{
int comboBoxCount = 0;
int HWND_PRINTER_NAME = 1;
List<IntPtr> ChildPtrList = GetChildWindows(hwnd_printDialog_in_Acrobat);
IntPtr hwnd = IntPtr.Zero;
for (int i = 0; i < ChildPtrList.Count; i++)
{
StringBuilder sClass = new StringBuilder();
GetClassName(ChildPtrList[i], sClass, 100);
if (sClass.ToString() == "ComboBox")
{
comboBoxCount++;
if (comboBoxCount == HWND_PRINTER_NAME)
{
hwnd = ChildPtrList[i];
break;
}
}
}
ChildPtrList.Clear();
int sSize;
sSize = (int)SendMessage(hwnd, WM_GETTEXTLENGTH, IntPtr.Zero, IntPtr.Zero) + 1;
StringBuilder sbTitle = new StringBuilder(sSize);
SendMessage(hwnd, WM_GETTEXT, (IntPtr)sSize, sbTitle);
return (sbTitle.ToString());
}
#region Code from http://pinvoke.net/default.aspx/user32/EnumChildWindows.html
[DllImport("user32")]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool EnumChildWindows(IntPtr window, EnumWindowProc callback, IntPtr i);
/// <summary>
/// Returns a list of child windows
/// </summary>
/// <param name="parent">Parent of the windows to return</param>
/// <returns>List of child windows</returns>
public static List<IntPtr> GetChildWindows(IntPtr parent)
{
List<IntPtr> result = new List<IntPtr>();
GCHandle listHandle = GCHandle.Alloc(result);
try
{
EnumWindowProc childProc = new EnumWindowProc(EnumWindow);
EnumChildWindows(parent, childProc, GCHandle.ToIntPtr(listHandle));
}
finally
{
if (listHandle.IsAllocated)
listHandle.Free();
}
return result;
}
/// <summary>
/// Callback method to be used when enumerating windows.
/// </summary>
/// <param name="handle">Handle of the next window</param>
/// <param name="pointer">Pointer to a GCHandle that holds a reference to the list to fill</param>
/// <returns>True to continue the enumeration, false to bail</returns>
private static bool EnumWindow(IntPtr handle, IntPtr pointer)
{
GCHandle gch = GCHandle.FromIntPtr(pointer);
List<IntPtr> list = gch.Target as List<IntPtr>;
if (list == null)
{
throw new InvalidCastException("GCHandle Target could not be cast as List<IntPtr>");
}
list.Add(handle);
// You can modify this to check to see if you want to cancel the operation, then return a null here
return true;
}
/// <summary>
/// Delegate for the EnumChildWindows method
/// </summary>
/// <param name="hWnd">Window handle</param>
/// <param name="parameter">Caller-defined variable; we use it for a pointer to our list</param>
/// <returns>True to continue enumerating, false to bail.</returns>
public delegate bool EnumWindowProc(IntPtr hWnd, IntPtr parameter);
#endregion
}
}