问如何使用后期绑定来获取excel实例？

EN

    [DllImport("Oleacc.dll")]
    private static extern int AccessibleObjectFromWindow(
        int hwnd, uint dwObjectID,
        byte[] riid,
        [MarshalAs(UnmanagedType.IUnknown)]ref object ptr);

// http://stackoverflow.com/questions/779363/how-to-use-use-late-binding-to-get-excel-instance
// ReSharper disable InconsistentNaming

using System;
using System.Runtime.InteropServices;
using System.Globalization;
using System.Reflection;
using System.Text;

namespace LateBindingWord {
    /// <summary> Interface definition for Word.Window interface </summary>
    [Guid("00020962-0000-0000-C000-000000000046")]
    [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
    public interface IWordWindow {
    }

    /// <summary>
    /// This class is needed as a workaround to http://support.microsoft.com/default.aspx?scid=kb;en-us;320369
    /// Excel automation will fail with the follwoing error on systems with non-English regional settings:
    /// "Old format or invalid type library. (Exception from HRESULT: 0x80028018 (TYPE_E_INVDATAREAD))" 
    /// </summary>
    class UiLanguageHelper : IDisposable {
        private readonly CultureInfo _currentCulture;

        public UiLanguageHelper() {
            // save current culture and set culture to en-US 
            _currentCulture = System.Threading.Thread.CurrentThread.CurrentCulture;
            System.Threading.Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
        }

        public void Dispose() {
            // reset to original culture 
            System.Threading.Thread.CurrentThread.CurrentCulture = _currentCulture;
        }
    }

    class Program {
        [DllImport("user32.dll", SetLastError = true)]
        static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

        [DllImport("Oleacc.dll")]
        static extern int AccessibleObjectFromWindow(int hwnd, uint dwObjectID, byte[] riid, out IWordWindow ptr);

        public delegate bool EnumChildCallback(int hwnd, ref int lParam);

        [DllImport("User32.dll")]
        public static extern bool EnumChildWindows(int hWndParent, EnumChildCallback lpEnumFunc, ref int lParam);

        [DllImport("User32.dll")]
        public static extern int GetClassName(int hWnd, StringBuilder lpClassName, int nMaxCount);

        public static bool EnumChildProc(int hwndChild, ref int lParam) {
            var buf = new StringBuilder(128);
            GetClassName(hwndChild, buf, 128);
            Console.WriteLine(buf.ToString());

            if (buf.ToString() == "_WwG") { 
                lParam = hwndChild;
                return false;
            }
            return true;
        }

        static void Main() {
            // Use the window class name ("XLMAIN") to retrieve a handle to Excel's main window.
            // Alternatively you can get the window handle via the process id:
            // int hwnd = (int)Process.GetProcessById(excelPid).MainWindowHandle;
            // var p=Process.GetProcesses().FirstOrDefault(x => x.ProcessName=="WINWORD");
            var hwnd = (int) FindWindow("OpusApp", null);

            if (hwnd == 0) 
                throw new Exception("Can't find Word");

            // Search the accessible child window (it has class name "_WwG") // http://msdn.microsoft.com/en-us/library/windows/desktop/dd317978%28v=vs.85%29.aspx
            var hwndChild = 0;
            var cb = new EnumChildCallback(EnumChildProc);
            EnumChildWindows(hwnd, cb, ref hwndChild);

            if (hwndChild == 0) 
                throw new Exception("Can't find Automation Child Window");

            // We call AccessibleObjectFromWindow, passing the constant OBJID_NATIVEOM (defined in winuser.h) 
            // and IID_IDispatch - we want an IDispatch pointer into the native object model.
            const uint OBJID_NATIVEOM = 0xFFFFFFF0;
            var IID_IDispatch = new Guid("{00020400-0000-0000-C000-000000000046}");
            IWordWindow ptr;

            var hr = AccessibleObjectFromWindow(hwndChild, OBJID_NATIVEOM, IID_IDispatch.ToByteArray(), out ptr);

            if (hr < 0) 
                throw new Exception("Can't get Accessible Object");

            // We successfully got a native OM IDispatch pointer, we can QI this for
            // an Excel Application using reflection (and using UILanguageHelper to 
            // fix http://support.microsoft.com/default.aspx?scid=kb;en-us;320369)
            using (new UiLanguageHelper()) {
                var wordApp = ptr.GetType().InvokeMember("Application", BindingFlags.GetProperty, null, ptr, null);

                var version = wordApp.GetType().InvokeMember("Version", BindingFlags.GetField | BindingFlags.InvokeMethod | BindingFlags.GetProperty, null, wordApp, null);
                Console.WriteLine("Word version is: {0}", version);

                dynamic wordAppd = ptr.GetType().InvokeMember("Application", BindingFlags.GetProperty, null, ptr, null);
                Console.WriteLine("Version: " + wordAppd.Version);
            }
        }
    }
}