程序代码：

#include <windows.h>
#include <stdio.h>
#include <richedit.h>


int main()
{
    CHARRANGE stcf;                  //定义结构，EM_EXSETSEL消息需要此消息，
    memset(&stcf,0,sizeof(stcf));      //并且将成员变量设置为 -1 是将光标置文本尾部
    stcf.cpMax = -1;
    stcf.cpMin = -1;
    wchar_t s[]=L"我是第一行数据\r\n我是第二行数据";
    int length1=wcslen(s);
    //printf("字符串长度为%d\n",length1);
    if (WinExec("c:\\windows\\wordpad.exe",SW_NORMAL)>31)
    {
        //printf("成功打开记事本进程\n");
        HWND notepadhandle= FindWindow(L"wordpad",NULL);
        if (notepadhandle!=0)
        {
            //printf("能够找到记事本主进程主窗体\n");
            HWND childhandle=FindWindowEx(notepadhandle,0,L"RichEdit20A",NULL);
            if (childhandle!=0)
            {
                //AppendTextToRich(s,length1,childhandle);
                SendMessage(childhandle,EM_EXSETSEL,0,(LPARAM)&stcf);   //向RICHEDIT控件发送EM_EXSETSEL消息，选中控件中所有字符
                SendMessage(childhandle,EM_REPLACESEL,0,(LPARAM)s);    //显示s字符

            }
        }

    }
    return 0;
}