[System.Security.SuppressUnmanagedCodeSecurity]
[DllImport("acad.exe", EntryPoint = "acedCmd", CallingConvention = CallingConvention.Cdecl)]
private static extern int acedCmd(IntPtr vlist);
[DllImport("acad.exe", EntryPoint = "acedCommand")]
private static extern int acedCommand(IntPtr vlist);//CAD2008和2008以前版本中的EntryPoint名称和2009以及2009之后的版本不一样
[DllImport("acad.exe", CharSet = CharSet.Auto, EntryPoint = "?acedPostCommand@@YAHPB_W@Z", CallingConvention = CallingConvention.Cdecl)]
private static extern int acedPostCommand(string strExpr);//CAD2008之后的版本中
[DllImport("acad.exe", CharSet = CharSet.Auto, EntryPoint = "?acedPostCommand@@YAHPEB_W@Z", CallingConvention = CallingConvention.Cdecl)]
private static extern int acedPostCommand(string strExpr);

[System.Security.SuppressUnmanagedCodeSecurity]
[DllImport("accore.dll", EntryPoint = "acedCmd", CallingConvention = CallingConvention.Cdecl)]
private static extern int acedCmd(IntPtr vlist);[DllImport("accore.dll", EntryPoint = "acedCommand")]
private static extern int acedCommand(IntPtr vlist);//CAD2008和2008以前版本中的EntryPoint名称和2009以及2009之后的版本不一样
[DllImport("accore.dll", CharSet = CharSet.Auto, EntryPoint = "?acedPostCommand@@YAHPB_W@Z", CallingConvention = CallingConvention.Cdecl)]
private static extern int acedPostCommand(string strExpr);
//CAD2008之后的版本中
[DllImport("accore.dll", CharSet = CharSet.Auto, EntryPoint = "?acedPostCommand@@YAHPEB_W@Z", CallingConvention = CallingConvention.Cdecl)]
private static extern int acedPostCommand(string strExpr);

ResultBuffer rb = new ResultBuffer();
rb.Add(new TypedValue((int)LispDataType.Text, "_.mycmd"));
int i = acedCmd(rb.UnmanagedObject);

//此处声明的委托和acedPostCommand(string strExpr)不相同是因为经过测试，如果参数声明为string类型，调用的时候传送到CAD的命令是乱码

public delegate int DelegateAcedPostCommand(byte[] cmd);
static DelegateAcedPostCommand pc;public void ShowMsg()
{//不同版本接口所在的程序模块不同string mdName = Application.Version.Major >= 19 ? "accore.dll" : "acad.exe";//CAD2007和2008中接口入口点名称不一样，2007以前的没有看，想看的可以用depends工具查看string apiName = (Application.Version.Major >= 17 && Application.Version.Minor <= 1) ? "?acedPostCommand@@YAHPB_W@Z" : "?acedPostCommand@@YAHPEB_W@Z";//获取当前CAD进程Process pro = Process.GetCurrentProcess();//获取CAD加载的所有程序模块（引用了什么DLL、EXE）ProcessModuleCollection pmc = pro.Modules;IntPtr iptr = IntPtr.Zero;for (int i = 0; i < pmc.Count; i++){ProcessModule pm = pmc[i];if (pm.ModuleName == mdName){iptr = pm.EntryPointAddress;break;}}if (iptr != IntPtr.Zero){pc = (DelegateAcedPostCommand)Marshal.GetDelegateForFunctionPointer(iptr, typeof(DelegateAcedPostCommand));if (pc != null){string str = "_.remmenu\n";//此处要把字符串使用Unicode编码转换为byte[]，然后再传入委托接口，不然到CAD之后会乱码byte[] bytes = Encoding.Unicode.GetBytes(str);int i = pc.Invoke(bytes);}}
}