关于字幕叠加（远程控制），如何实现？[c#][海康]

Question

       [StructLayout(LayoutKind.Sequential, Pack = 1, CharSet = CharSet.Ansi)]
        public struct NET_DVR_SHOWSTRINGINFO
        {
            //编码端字符叠加配置结构 
            public ushort dwShowString;
            public int wStringSize;
            public ushort wShowStringTopLeftX;
            public ushort wShowStringTopLeftY;
            //[MarshalAs(UnmanagedType.LPArray, SizeConst = 44)]
            //public char[] sString;            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 44)]
            public string sString;        }
        [StructLayout(LayoutKind.Sequential)]
        public struct NET_DVR_SHOWSTRING
        {
            //叠加字符结构
            public int dwSize;
            public NET_DVR_SHOWSTRINGINFO struStringInfo;
        }
        //编码端叠加字符
        [DllImport("HCNetSDK.dll")]
        public static extern bool NET_DVR_SetDVRConfig(int lUserID, int dwCommand, int lChannel, NET_DVR_SHOWSTRING lpInBuffer, int dwInBufferSize);
        private void button5_Click(object sender, EventArgs e)
        {
            NET_DVR_SHOWSTRINGINFO _showstringinfo = new NET_DVR_SHOWSTRINGINFO();            NET_DVR_SHOWSTRING _showstring = new NET_DVR_SHOWSTRING();            string strTT = "我是来测试的!";            _showstring.dwSize = 1;
            _showstring.struStringInfo = _showstringinfo;
            _showstring.struStringInfo.dwShowString = 1;
            _showstring.struStringInfo.sString = strTT;
            _showstring.struStringInfo.wStringSize = strTT.Length;
            _showstring.struStringInfo.wShowStringTopLeftX = 100;
            _showstring.struStringInfo.wShowStringTopLeftY = 100;            int iSize= Marshal.SizeOf(_showstring);            bool bac = NET_DVR_SetDVRConfig(iLoginRef, 131, 0, _showstring, iSize);
            if (bac == false)
            {
                MessageBox.Show("失败");
            }
         }
不知道为什么，一直失败，做过的帮个忙看看！！
/*****************************DS-6001D/F(end)***************************///单字符参数(子结构)
typedef struct 
{
WORD wShowString; // 预览的图象上是否显示字符,0-不显示,1-显示 区域大小704*576,单个字符的大小为32*32
WORD wStringSize; /* 该行字符的长度，不能大于44个字符 */
WORD wShowStringTopLeftX; /* 字符显示位置的x坐标 */
WORD wShowStringTopLeftY; /* 字符名称显示位置的y坐标 */
char sString[44]; /* 要显示的字符内容 */
}NET_DVR_SHOWSTRINGINFO, *LPNET_DVR_SHOWSTRINGINFO;//叠加字符(9000扩展)
typedef struct 
{
DWORD dwSize;
NET_DVR_SHOWSTRINGINFO struStringInfo[MAX_STRINGNUM_V30]; /* 要显示的字符内容 */
}NET_DVR_SHOWSTRING_V30, *LPNET_DVR_SHOWSTRING_V30;//叠加字符扩展(8条字符)
typedef struct 
{
DWORD dwSize;
NET_DVR_SHOWSTRINGINFO struStringInfo[MAX_STRINGNUM_EX]; /* 要显示的字符内容 */
}NET_DVR_SHOWSTRING_EX, *LPNET_DVR_SHOWSTRING_EX;//叠加字符
typedef struct 
{
DWORD dwSize;
NET_DVR_SHOWSTRINGINFO struStringInfo[MAX_STRINGNUM]; /* 要显示的字符内容 */
}NET_DVR_SHOWSTRING, *LPNET_DVR_SHOWSTRING;/*********************************************************
  Function: OnBnClickedBtnStringOk
  Desc: finish text overlay settings
  Input:
  Output:
  Return:
**********************************************************/
void CDlgRemoteShowString::OnBnClickedBtnStringOk()
{
UpdateData(TRUE);
char szLan[128] = {0};
int i = m_comboShowArea.GetCurSel();
m_struShowString.struStringInfo[i].wShowString = (WORD)m_bChkShow;
memcpy(m_struShowString.struStringInfo[i].sString, m_csString, 44);
m_struShowString.struStringInfo[i].wStringSize = (WORD)strlen(m_csString);
m_struShowString.struStringInfo[i].wShowStringTopLeftX = (WORD)m_iStringX;
m_struShowString.struStringInfo[i].wShowStringTopLeftY = (WORD)m_iStringY;
if (!NET_DVR_SetDVRConfig(m_lLoginID, NET_DVR_SET_SHOWSTRING_V30, m_iChanShowNum, &m_struShowString, sizeof(NET_DVR_SHOWSTRING_V30)))
{
g_pMainDlg->AddLog(g_pMainDlg->m_iCurDeviceIndex, OPERATION_FAIL_T, "NET_DVR_SET_SHOWSTRING_V30");
g_StringLanType(szLan, "设置字符参数失败", "Failure to set character parameters");
AfxMessageBox(szLan);
return ;
}
g_pMainDlg->AddLog(g_pMainDlg->m_iCurDeviceIndex, OPERATION_SUCC_T, "NET_DVR_SET_SHOWSTRING_V30");
}

Answer 1

int iSize= Marshal.SizeOf(_showstring); 转换问题

Answer 2

//叠加字符
typedef struct 
{
    DWORD dwSize;
    NET_DVR_SHOWSTRINGINFO struStringInfo[MAX_STRINGNUM];                /* 要显示的字符内容 */
}NET_DVR_SHOWSTRING, *LPNET_DVR_SHOWSTRING;
这个在C#中如何初始化，并且定义呢？？

Answer 3

解决了， 分享一下：[System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
        public struct NET_DVR_SHOWSTRING_V30
        {
            /// <summary>
            /// 结构体大小
            /// </summary>
            public int dwSize;
            /// <summary>
            /// 要显示的字符内容
            /// </summary>
            [MarshalAsAttribute(UnmanagedType.ByValArray, SizeConst = 8)]
            public NET_DVR_SHOWSTRINGINFO[] struStringInfo;
        };        [StructLayoutAttribute(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
        public struct NET_DVR_SHOWSTRINGINFO
        {
            /// <summary>
            /// 预览的图象上是否显示字符,0-不显示,1-显示 区域大小704*576,单个字符的大小为32*32
            /// </summary>
            public ushort wShowString;
/// <summary>
            /// 该行字符的长度，不能大于44个字符
/// </summary>
            public ushort wStringSize;
/// <summary>
            /// 字符显示位置的x坐标
/// </summary>
            public ushort wShowStringTopLeftX;
            /// <summary>
            /// 字符名称显示位置的y坐标
            /// </summary>
            public ushort wShowStringTopLeftY;
        /// <summary>
            /// 要显示的字符内容
        /// </summary>
            [MarshalAsAttribute(UnmanagedType.ByValTStr, SizeConst = 44)]
            public string sString;     
        }//设置服务器参数
        [DllImport("HCNetSDK.dll")]
        public static extern int NET_DVR_SetDVRConfig(int lUserID, int dwCommand, int lChannel, IntPtr lpInBuffer, int dwInBufferSize);
        
        [DllImport("HCNetSDK.dll")]
        public static extern int NET_DVR_GetDVRConfig(int lUserID, int dwCommand, int lChannel, IntPtr lpInBuffer, int dwInBufferSize, ref int len);NET_DVR_SHOWSTRING_V30 ShowStruct = new NET_DVR_SHOWSTRING_V30();
            int len = 0;
            IntPtr ptr = Marshal.AllocCoTaskMem(Marshal.SizeOf(ShowStruct));
            Marshal.StructureToPtr(ShowStruct, ptr, false);
            int err = NET_DVR_GetDVRConfig(UserID, 1030, 1, ptr, Marshal.SizeOf(ShowStruct), ref len);            ShowStruct = (NET_DVR_SHOWSTRING_V30)Marshal.PtrToStructure(ptr, typeof(NET_DVR_SHOWSTRING_V30));
            ShowStruct.struStringInfo[0].sString = "Yan";
            ShowStruct.struStringInfo[0].wShowString = 1;
            ShowStruct.struStringInfo[0].wShowStringTopLeftX = 10;
            ShowStruct.struStringInfo[0].wShowStringTopLeftY = 10;
            ShowStruct.struStringInfo[0].wStringSize = 3;            IntPtr ptrNow = Marshal.AllocCoTaskMem(Marshal.SizeOf(ShowStruct));
            Marshal.StructureToPtr(ShowStruct, ptrNow, false);
            err = NET_DVR_SetDVRConfig(UserID, 1031, 1, ptrNow, Marshal.SizeOf(ShowStruct));            return err;