利用COPYDATASTRUCT传递命令行参数给驻留内存的进程（SendMessage应用）

我们知道Window进程之间通过API的SendMessage方法传递消息。但是方法参数lParam是Long型，那么如果传递一个字符串（譬如命令行参数）应该怎么办呢，甚至一个对象、结构呢。VB的发送接收需要通过传递指针实现（换言之是字符串的内存地址），下面总结VB方式、C#方式各自如何实现消息的发送与接收；各自是可以互换的，譬如C#发送的消息，VB窗口可以收到；相反亦可以。当然同种语言之间更加没问题了。

VB发送端 Form1.frm：

Option Explicit

Private Type COPYDATASTRUCT
    dwData As Long
    cbData As Long
    lpData As Long
End Type
  
Private Const WM_COPYDATA = &H4A
  
Private Declare Function FindWindow Lib "user32" Alias _
   "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName _
   As String) As Long
  
Private Declare Function SendMessage Lib "user32" Alias _
   "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal _
   wParam As Long, lParam As Any) As Long
  
'Copies a block of memory from one location to another.
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" _
   (hpvDest As Any, hpvSource As Any, ByVal cbCopy As Long)
  
Private Sub Command1_Click()
    Dim cds As COPYDATASTRUCT
    Dim ThWnd As Long
    Dim buf(1 To 1024) As Byte
    Dim a As String, i As Long, lLen As Long
  
    ' Get the hWnd of the target application
    ThWnd = FindWindow(vbNullString, "Target")
    a$ = "It Works on " & Format(Now, "yyyy-MM-dd HH:mm:ss") & " !"
    ' Copy the string into a byte array, converting it to ASCII
    lLen = LenB(StrConv(a, vbFromUnicode))
    Call CopyMemory(buf(1), ByVal a, lLen)
    cds.dwData = 3
    cds.cbData = lLen + 1
    cds.lpData = VarPtr(buf(1))
    i = SendMessage(ThWnd, WM_COPYDATA, Me.hwnd, cds)
End Sub
  
Private Sub Form_Load()
    ' This gives you visibility that the target app is running
    ' and you are pointing to the correct hWnd
    Me.Caption = Hex$(FindWindow(vbNullString, "Target"))
End Sub

VB接收端

1。MsgHook.bas：

Option Explicit

Type COPYDATASTRUCT
    dwData As Long
    cbData As Long
    lpData As Long
End Type
 
Public Const GWL_WNDPROC = (-4)
Public Const WM_COPYDATA = &H4A
Global lpPrevWndProc As Long
Global gHW As Long
 
'Copies a block of memory from one location to another.
Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" _
   (hpvDest As Any, hpvSource As Any, ByVal cbCopy As Long)
 
Declare Function CallWindowProc Lib "user32" Alias _
   "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hwnd As _
   Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As _
   Long) As Long
 
Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _
   (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As _
   Long) As Long
 
Public Sub Hook()
    lpPrevWndProc = SetWindowLong(gHW, GWL_WNDPROC, _
    AddressOf WindowProc)
    Debug.Print lpPrevWndProc
End Sub
 
Public Sub Unhook()
    Dim temp As Long
    temp = SetWindowLong(gHW, GWL_WNDPROC, lpPrevWndProc)
End Sub
 
Function WindowProc(ByVal hw As Long, ByVal uMsg As Long, _
   ByVal wParam As Long, ByVal lParam As Long) As Long
    If uMsg = WM_COPYDATA Then
        Call mySub(lParam)
    End If
    WindowProc = CallWindowProc(lpPrevWndProc, hw, uMsg, wParam, lParam)
End Function
 
Sub mySub(lParam As Long)
    Dim cds As COPYDATASTRUCT
    Dim buf(1 To 1024) As Byte
    Dim a As String
 
    Call CopyMemory(cds, ByVal lParam, Len(cds))
 
    Select Case cds.dwData
     Case 1
        Debug.Print "got a 1"
     Case 2
        Debug.Print "got a 2"
     Case 3
        Call CopyMemory(buf(1), ByVal cds.lpData, cds.cbData)
        a$ = StrConv(buf, vbUnicode)
        a$ = Left$(a$, InStr(1, a$, Chr$(0)) - 1)
        Form1.Label1.Caption = a$
    End Select
End Sub

2。Target.frm：

Option Explicit

Private Sub Form_Load()
    gHW = Me.hwnd
    Hook
    Me.Caption = "Target"
    Me.Show
    Label1.Caption = Hex$(gHW)
End Sub
  
Private Sub Form_Unload(Cancel As Integer)
    Unhook
End Sub

C#的发送端：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Runtime.InteropServices;

namespace CSMsgSender
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            int hwnd = FindWindow(null, "Target");
            if (hwnd != 0)
            {
                string str = "It Works on " + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + " !";
                byte[] arr = System.Text.Encoding.Default.GetBytes(str);
                int len = arr.Length;
                COPYDATASTRUCT cdata;
                cdata.dwData = 3;
                cdata.lpData = str;
                cdata.cbData = len + 1;
                SendMessage(hwnd, WM_COPYDATA, 10, ref cdata);
            }
        }

        [DllImport("User32.dll")]
        public static extern int SendMessage(int hwnd, int msg, int wParam, ref COPYDATASTRUCT lParam);
        [DllImport("User32.dll")]
        public static extern int FindWindow(string lpClassName, string lpWindowName);

        private const int WM_COPYDATA = 0x004A;
        public struct COPYDATASTRUCT
        {
            public int dwData;
            public int cbData;
            [MarshalAs(UnmanagedType.LPStr)]
            public string lpData;
        }
    }
}

C#接收端：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace CSMsgReceiver
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.Text = "Target";
        }

        protected override void DefWndProc(ref Message m)
        {
            switch (m.Msg)
            {
                case WM_COPYDATA:
                    COPYDATASTRUCT cdata = new COPYDATASTRUCT();
                    Type mytype = cdata.GetType();
                    cdata = (COPYDATASTRUCT)m.GetLParam(mytype);
                    this.textBox1.Text = cdata.lpData;
                    break;
                default:
                    base.DefWndProc(ref m);
                    break;
            }
        }

        //WM_COPYDATA消息的主要目的是允许在进程间传递只读数据。
        private const int WM_COPYDATA = 0x004A;

        //Windows在通过WM_COPYDATA消息传递期间，不提供继承同步方式。
        //其中,WM_COPYDATA对应的十六进制数为0x004A
        public struct COPYDATASTRUCT
        {
            public int dwData;
            public int cbData;
            [MarshalAs(UnmanagedType.LPStr)]
            public string lpData;
        }
    }
}