当我设置COPYDATASTRUCT时，我设置了 {
dwData = new IntPtr(0)
} ，发送方将成功向接收方发送消息。但是，当我尝试 {
dwData = new IntPtr(xxOtherNumbersxxx)
} ，它不会奏效。谁能向我解释一下dwData在这里做了什么？谢谢！
（P.S。我是一名新手软件工程师，有着非常热情的学习心态，所以要对我的评分保持温和...... PLZ .....）
以下是我在C＃中的发件人的源代码：
using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Windows.Forms;
// this application is a Sender
// made to work with a Receiver that is already made in Pascal by xxxxxx
// The Receiver is located at
// "K:\xxxxxxxxxxx"
//
// This application is meant to send string "Hello World" to the Receiver
// if successful, the Receiver would appear on screen:
//
// WM_CopyData from: 3819
// Received string "Hello World!" at 6/3/2015
//
// Application:
// 1. Put "Hello World!" message into a data structure called "COPYDATASTUCT"
// 2. Find receiver by its app title "ReceiverMainForm" and its Class "TReceiverMainForm" (debug window: a pop-up window should show up with non-zero integers)
// 3. Send message in COPYDATASTRUCT through WM_COPYDATA code to receiver
namespace FindNotepad
{
class Program
{
//include SendMessage
[DllImport("user32.dll")]
public static extern int SendMessage(IntPtr hWnd, int uMsg, int wParam, ref COPYDATASTRUCT lParam);
//include SendMessage
[DllImport("user32.dll")]
public static extern IntPtr FindWindow(string lpszClass, string lpszWindow);
//this is a constant indicating the window that we want to send a text message
const int WM_COPYDATA = 0x004A;
static void Main(string[] args)
{
// ---------------- 1. set up message to be sent -----------------------
//Put "Hello World!" message into a data structure called "COPYDATASTUCT"
string msg = "Hello World!";
var cds = new COPYDATASTRUCT
{
dwData = new IntPtr(0),
cbData = msg.Length + 1,
lpData = msg
};
// ---------------- 2. Find receiver application window -----------------------
IntPtr receiverHandle = FindWindow("TReceiverMainForm", "ReceiverMainForm");
// debug window pop-up
MessageBox.Show(receiverHandle.ToString());
// ---------------- 3. send message to receiver -----------------------
try
{
SendMessage(receiverHandle, WM_COPYDATA, 3819, ref cds);
// receiverHandle: handle for the receiver window
// WM_COPYDATA: an application that sends WM_COPYDATA message to pass data to another application
// 3819: handle of sender application, any preset integer can work. This is to distinguish which sender sends message on the receiver
// ref cds: data structure that contains the message to be sent.
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
//Used for WM_COPYDATA for string messages
public struct COPYDATASTRUCT
{
//dwData
//The data to be passed to the receiving application.
public IntPtr dwData;
// cbData
// The size, in bytes, of the data pointed to by the lpData member.
public int cbData;
// lpDATA
// The data to be passed to the receiving application. This member can be NULL.
public string lpData;
}
}
}