C#查找指定窗口的子窗口的句柄

用axWebBrowser加载HTML网页时，真正显示内容的窗体并不是axWebBrowser，而是其子窗口的子窗口一个名为Internet Explorer_Server的类。从spy++可知:

公司需要在网页上进行手写，需要对Internet Explorer_Server进行操作，而通过axWebBrowser的Handle不能直接操作Internet Explorer_Server。于是在网上搜到Paul DiLascia写的一个CFindWnd类，是用C++写的，由于我用C#进行了改写。

这个类主要用的的API 是EnumChildWindows和FindWindowEx，第一个遍历指定窗口下的子窗口，第二个查找指定名称的窗口，如果找到返回此窗口Handle。

该类的用法：

FindWindow fw = new FindWindow(wndHandle, "ChildwndClassName"); //实例化，第一个参数是要查找的起始窗口的句柄；第二个参数是要查找的窗口的类的名称。现在我们需要的传的是"Internet Explorer_Server"。

IntPtr ip = fw.FoundHandle;//FindWindow的公共属性FoundHandle就是查找到的窗口的句柄。

完整的类如下：

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace SystemManager.Utility
{
    /**/
    /// <summary>
    /// This class is to find the given window's child window accroding to the given child window's name.
    /// The useage: FindWindow fw = new FindWindow(wndHandle, "ChildwndClassName"); IntPtr ip = fw.FoundHandle;
    /// I adapt the code from Paul DiLascia,who is the MSDN Magazine's writer.
    /// The original class is named CFindWnd which is written in C++, and you could get it on Internet.
    /// www.pinvoke.net is a great website.It includes almost all the API fuctoin to be used in C#.
    /// </summary>
    class FindWindow
    {
        [DllImport("user32")]
        [return: MarshalAs(UnmanagedType.Bool)]
        //IMPORTANT : LPARAM  must be a pointer (InterPtr) in VS2005, otherwise an exception will be thrown
        private static extern bool EnumChildWindows(IntPtr window, EnumWindowProc callback, IntPtr i);
        //the callback function for the EnumChildWindows
        private delegate bool EnumWindowProc(IntPtr hWnd, IntPtr parameter);

        //if found  return the handle , otherwise return IntPtr.Zero
        [DllImport("user32.dll", EntryPoint = "FindWindowEx")]
        private static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

        private string m_classname; // class name to look for

        private IntPtr m_hWnd; // HWND if found
        public IntPtr FoundHandle
        {
            get { return m_hWnd; }
        }
        // ctor does the work--just instantiate and go
        public FindWindow(IntPtr hwndParent, string classname)
        {
            m_hWnd = IntPtr.Zero;
            m_classname = classname;
            FindChildClassHwnd(hwndParent, IntPtr.Zero);
        }

        /**/
        /// <summary>
        /// Find the child window, if found m_classname will be assigned 
        /// </summary>
        /// <param name="hwndParent">parent's handle</param>
        /// <param name="lParam">the application value, nonuse</param>
        /// <returns>found or not found</returns>
        //The C++ code is that  lParam is the instance of FindWindow class , if found assign the instance's m_hWnd
        private bool FindChildClassHwnd(IntPtr hwndParent, IntPtr lParam)
        {
            EnumWindowProc childProc = new EnumWindowProc(FindChildClassHwnd);
            IntPtr hwnd = FindWindowEx(hwndParent, IntPtr.Zero, this.m_classname, string.Empty);
            if (hwnd != IntPtr.Zero)
            {
                this.m_hWnd = hwnd; // found: save it
                return false; // stop enumerating
            }
            EnumChildWindows(hwndParent, childProc, IntPtr.Zero); // recurse  redo FindChildClassHwnd
            return true;// keep looking
        }
    }
}

注意：在VS2005中，MDA检查的很严格，LPARAM是64位，要用IntPtr表示(网上有人用long来表示，我试了，MDA会抛出异常)。http://pinvoke.net/ 是个不错的网站，它包含了几乎所有的API在.NET中的调用说明，还有例子。

附Paul DiLascia用C++写的CFindWnd类：

////////////////////////////////////////////////////////////////
// MSDN Magazine -- August 2003
// If this code works, it was written by Paul DiLascia.
// If not, I don't know who wrote it.
// Compiles with Visual Studio .NET on Windows XP. Tab size=3.
//
// ---
// This class encapsulates the process of finding a window with a given class name
// as a descendant of a given window. To use it, instantiate like so:
//
// CFindWnd fw(hwndParent,classname);
//
// fw.m_hWnd will be the HWND of the desired window, if found.
//
class CFindWnd {
  private:
        /**///////////////////
        // This private function is used with EnumChildWindows to find the child
        // with a given class name. Returns FALSE if found (to stop enumerating).
        //
        static BOOL CALLBACK FindChildClassHwnd(HWND hwndParent, LPARAM lParam) {
              CFindWnd *pfw = (CFindWnd*)lParam;
                HWND hwnd = FindWindowEx(hwndParent, NULL, pfw->m_classname, NULL);
                  if (hwnd) {
                        pfw->m_hWnd = hwnd; // found: save it
                          return FALSE; // stop enumerating
                    }
                    EnumChildWindows(hwndParent, FindChildClassHwnd, lParam); // recurse
                      return TRUE; // keep looking
          }
  public:
        LPCSTR m_classname; // class name to look for
          HWND m_hWnd; // HWND if found
            // ctor does the work--just instantiate and go
            CFindWnd(HWND hwndParent, LPCSTR classname)
                  : m_hWnd(NULL), m_classname(classname)
              {
                    FindChildClassHwnd(hwndParent, (LPARAM)this);
              }
  };

2009年更新
通过实验得知，FindWindowEx可以通过classname或caption（也就是窗口的title）查找窗口，且如果第一个参数传IntPtr.Zero的话，将从Windows最顶层窗口开始查找，但是窗口很多的话这样会非常的慢，所以加入Timeout的判断，如果超时还没找到，返回false。

用法：FindWindow fw = new FindWindow(IntPtr.Zero, null, "ThunderDFrame", 10);//查找Title为ThunderDFrame的窗口，如果10秒内还没找到，返回false

代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace Util
{
    class FindWindow
    {
        [DllImport("user32")]
        [return: MarshalAs(UnmanagedType.Bool)]
        //IMPORTANT : LPARAM  must be a pointer (InterPtr) in VS2005, otherwise an exception will be thrown
        private static extern bool EnumChildWindows(IntPtr window, EnumWindowProc callback, IntPtr i);
        //the callback function for the EnumChildWindows
        private delegate bool EnumWindowProc(IntPtr hWnd, IntPtr parameter);

        //if found  return the handle , otherwise return IntPtr.Zero
        [DllImport("user32.dll", EntryPoint = "FindWindowEx")]
        private static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

        private string m_classname; // class name to look for
        private string m_caption; // caption name to look for

        private DateTime start;
        private int m_timeout;//If exceed the time. Indicate no windows found.

        private IntPtr m_hWnd; // HWND if found
        public IntPtr FoundHandle
        {
            get { return m_hWnd; }
        }

        private bool m_IsTimeOut;
        public bool IsTimeOut
        {
            get{return m_IsTimeOut;}
            set { m_IsTimeOut = value; }
        }

        // ctor does the work--just instantiate and go
        public FindWindow(IntPtr hwndParent, string classname, string caption, int timeout)
        {
            m_hWnd = IntPtr.Zero;
            m_classname = classname;
            m_caption = caption;
            m_timeout = timeout;
            start = DateTime.Now;
            FindChildClassHwnd(hwndParent, IntPtr.Zero);
        }

        /**/
        /// <summary>
        /// Find the child window, if found m_classname will be assigned 
        /// </summary>
        /// <param name="hwndParent">parent's handle</param>
        /// <param name="lParam">the application value, nonuse</param>
        /// <returns>found or not found</returns>
        //The C++ code is that  lParam is the instance of FindWindow class , if found assign the instance's m_hWnd
        private bool FindChildClassHwnd(IntPtr hwndParent, IntPtr lParam)
        {
            EnumWindowProc childProc = new EnumWindowProc(FindChildClassHwnd);
            IntPtr hwnd = FindWindowEx(hwndParent, IntPtr.Zero, m_classname, m_caption);
            if (hwnd != IntPtr.Zero)
            {
                this.m_hWnd = hwnd; // found: save it
                m_IsTimeOut = false;
                return false; // stop enumerating
            }

            DateTime end = DateTime.Now;

            if (start.AddSeconds(m_timeout) < end)
            {
                m_IsTimeOut = true;
                return false;
            }

            EnumChildWindows(hwndParent, childProc, IntPtr.Zero); // recurse  redo FindChildClassHwnd
            return true;// keep looking
        }
    }
}