利用API发送和接收消息，本代码测试全通过

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

namespace Set_Get_Messages
{
class APISendMsg
{
#region 常数
const int WM_COPYDATA = 0x004A;//发送消息到窗口
const int WM_SETTEXT = 0xC;//发送消息到控件
const int WM_CLOSE = 0x0010;//关闭窗口
const int BM_CLICK = 0xF5;//点击窗体
public const int WM_GETTEXT = 0x000D;//得到消息
#endregion
#region API函数
//查找窗体
[DllImport("user32.dll", EntryPoint = "FindWindow", CharSet = CharSet.Auto)]
public static extern IntPtr FindWindow(String classname, String text);
//查找子窗体
[DllImport("User32.dll", EntryPoint = "FindWindowEx", CharSet = CharSet.Auto)]
public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpClassName, string lpWindowName);

/// <summary>
/// 将指定的消息发送到一个或多个窗口
/// </summary>
/// <param name="hwnd">目标窗口句柄</param>
/// <param name="msg">消息类型</param>
/// <param name="hwndFrom">返回的消息</param>
/// <param name="cd">发送的消息</param>
/// <returns></returns>
[DllImport("user32.dll", EntryPoint = "SendMessage")]
public static extern long SendMessage(IntPtr hwnd, Int32 msg, Int32 hwndFrom, ref COPYDATASTRUCT cd);
[DllImport("user32.dll", EntryPoint = "SendMessage")]
public static extern int SendMessage(IntPtr hwnd, int wMsg, int wParam, int lParam);
/// <summary>
/// 将指定的消息发送到一个或多个窗体
/// </summary>
/// <param name="hWnd">窗体句柄</param>
/// <param name="Msg">消息类别</param>
/// <param name="wParam">返回消息</param>
/// <param name="lParam">发送的消息</param>
/// <returns></returns>
[DllImport("user32.dll", EntryPoint = "SendMessage")]
public static extern long SendMessage(IntPtr hWnd, Int32 Msg, Int32 wParam, [MarshalAs(UnmanagedType.LPStr)] string lParam);

//获取消息
[DllImport("user32.dll", EntryPoint = "SendMessage")]
public static extern bool SendMessageSetText(IntPtr hwnd, uint wMsg, uint wParam, string lParam);
[DllImport("user32.dll", EntryPoint = "SendMessage")]
public static extern int SendMessageGetText(IntPtr hwnd, uint wMsg, uint wParam, StringBuilder lParam);

#endregion
#region 发送消息
//发送消息结构体
[StructLayout(LayoutKind.Sequential)]
public struct COPYDATASTRUCT
{
public IntPtr dwData;//目标
public int cbData;//数据长度
[MarshalAs(UnmanagedType.LPStr)]
public string lpData;//消息
}

/// <summary>
/// 发送消息
/// </summary>
/// <param name="strMsg">消息</param>
/// <returns>成功非0，失败0</returns>
public static long API_sendMsgWindows(IntPtr windowHwnd, string strMsg)
{
long longResult = 0;
if (windowHwnd != IntPtr.Zero && !string.IsNullOrEmpty(strMsg.Replace(" ", "")))
{
//定义c,是为了取得字符串中一些非英文字符的长度，比如一个中文，占两个字长。
int longMsg = StrLength(strMsg);
Int32 id = 1;
COPYDATASTRUCT cd = new COPYDATASTRUCT();
cd.dwData = (IntPtr)id;
cd.lpData = strMsg + "/$";//一定要加上结束标志，不加的话会得到不确定的字符。
cd.cbData = strMsg.Length + longMsg + 2;//另外加上双字节的东西和结束符的长度
//发送消息
longResult = SendMessage(windowHwnd, WM_COPYDATA, 0, ref cd);
}
return longResult;
}

/// <summary>
/// 字符串长度(按字节算)
/// </summary>
/// <param name="str"></param>
/// <returns>字符串长度</returns>
private static int StrLength(string str)
{
int len = 0;
byte[] b;
if (!string.IsNullOrEmpty (str.Replace(" ","")))
{
for (int i = 0; i < str.Length; i++)
{
b = Encoding.Default.GetBytes(str.Substring(i, 1));//每个字
if (b.Length > 1)
len += 2;
else
len++;
}
}

return len;
}
#endregion
#region 得到窗体消息
/// <summary>
/// 取得指定句柄的窗口的Caption字符串
/// </summary>
/// <param name="hWnd"></param>
/// <param name="strWndText"></param>
/// <returns></returns>
public static int GetWindowControlTextX(IntPtr hWnd, out string strWndText)
{
/*
StringBuffer sLimitedString;
int nLen = GetWindowText(hWnd, out sLimitedString, 256);
if (nLen > 0)
strWndText = sLimitedString.szText;
else
strWndText = @"";

return nLen;
*/
//由于针对不同的进程的窗体控件，不能使用GetWindowText函数，只能使用WM_GETTEXT
StringBuilder strBuffer = new StringBuilder(1024);
int nLen = SendMessageGetText(hWnd,WM_GETTEXT, 1024, strBuffer);
strWndText = strBuffer.ToString();
return nLen;
}
#endregion
#region 共用方法
/// <summary>
/// 为控件赋值
/// </summary>
/// <param name="childControID">控件句柄</param>
/// <param name="strMsg">消息</param>
/// <returns>成功非0，失败0</returns>
public static long API_SetTextValue(IntPtr childControID, string strMsg)
{
long longResult = 0;
if (childControID != IntPtr.Zero && !string.IsNullOrEmpty(strMsg.Replace(" ", "")))
{
longResult = SendMessage(childControID, WM_SETTEXT, 0, strMsg);
}
return longResult;
}
/// <summary>
/// 点击控件
/// </summary>
/// <param name="childControID">按钮控件句柄</param>
/// <returns>成功非0，失败0</returns>
public static long API_ClickButton(IntPtr childControID)
{
long longResult = 0;
if (childControID != IntPtr.Zero)
{
longResult = SendMessage(childControID, BM_CLICK, 0, 0);
}
return longResult;
}

#endregion
}
}

//补

//另一种比较稳定的方法接收窗体中的代码

//自动接收消息
[StructLayout(LayoutKind.Sequential)]
public struct COPYDATASTRUCT
{
public IntPtr dwData;
public int cbData;
public IntPtr lpData;
}

protected override void DefWndProc(ref Message m)
{
try
{
switch (m.Msg)
{
//接收CopyData消息，读取发送过来的数据
case WM_COPYDATA:
COPYDATASTRUCT cds = new COPYDATASTRUCT();
Type mytype = cds.GetType();
cds = (COPYDATASTRUCT)m.GetLParam(mytype);
uint flag = (uint)(cds.dwData);
byte[] bt = new byte[cds.cbData];
Marshal.Copy(cds.lpData, bt, 0, bt.Length);
if (cds.cbData > 0)
{
string tmp = System.Text.Encoding.Default.GetString(bt);
if (!string.IsNullOrEmpty(tmp))
{
//交易方法
getRunPlan(tmp);
}
}
// MessageBox.Show(tmp);
break;
default:
base.DefWndProc(ref m);
break;
}
}
catch (Exception ex)
{
XtraMessageBox.Show(ex.ToString(), "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
// throw ex;
}
}

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