am calling win32 dll in the program I wrote in c# project but System.AccessViolationException: 'An attempt was made to read or write to protected memory. This is usually an indication that other memory is corrupt.' error . Error Screen DLL Calling Screen What could be the cause of this error? Although I made adjustments in the debug section as follows, it did not get better.

Visual Studio Debug Section

How should I use a file with win32 dll for C# (I know the functions in this file)

can you help me?

The codes are as follows.

1- Function where DLL is called

public static class Ziton_Function_Library
{
    [DllImport(".\\2010-2W32.dll",EntryPoint = "FP10_ConnectTCPIP",CharSet =CharSet.Auto)]
    internal static extern int EEC_FP10_ConnectTCPIP(char strIP, int wPort, int wIdPanel, long dwPassword, long dwTimeout, long dwConnTimeout, out int nError);
}

2- Function encountered with error in the program

private void ConnectTcpIp_Click(object sender, EventArgs e)
{
    String strPassword, strPanelId, strTimeOut, strConnTimeOut;
    String strIP, strPort;
    int nPort, m_nIdPanelTCPIP,nError;
    long nPassword, nTimeOut, nConnTimeOut;
    Char nStrIP;
    IntPtr m_nIdSessionTCPIP;

    Tb_Password.Text = "1234";
    Tb_PanelID.Text = "1";
    Tb_ConnectionTimedOut.Text = "3000";
    Tb_IPadress.Text = "192.168.104.140";
    Tb_PanelPort.Text = "2505";

    strPassword = Tb_Password.Text;
    strPanelId = Tb_PanelID.Text;
    strTimeOut = "0";
    strConnTimeOut = Tb_ConnectionTimedOut.Text;
    strIP = Tb_IPadress.Text;
    strPort = Tb_PanelPort.Text;

    nPort = Convert.ToInt16(strPort);
    m_nIdPanelTCPIP = Convert.ToInt16(strPanelId);
    nPassword = Convert.ToInt32(strPassword);
    nTimeOut = Convert.ToInt32(strTimeOut);
    nConnTimeOut = Convert.ToInt32(strConnTimeOut);
    if (!string.IsNullOrEmpty(strIP) && strIP.Trim().Length == 1)
        nStrIP = System.Convert.ToChar(strIP);
    else
    {
        nStrIP = strIP.FirstOrDefault(); // if thats what your logic
    }
    //nStrIP = Convert.ToChar(strIP);
    nError = 0;
            
    Cursor.Current = Cursors.WaitCursor;
    m_nIdSessionTCPIP = (IntPtr)Ziton_Function_Library.EEC_FP10_ConnectTCPIP(nStrIP, nPort, m_nIdPanelTCPIP, nPassword, nTimeOut, nConnTimeOut, out nError);
    Cursor.Current = Cursors.Default;

    Tb_SessionID.Text = Convert.ToString(m_nIdSessionTCPIP);

    switch (nError)
    {
        case 0:
            Tb_ConnectionStatus.Text = "Connected";
            Tb_ConnectionStatus.BackColor = Color.Lime;
            Tb_ConnectionStatus.ForeColor = Color.Black;
            return;

        case 2:
            Tb_ConnectionStatus.Text = "Socket Error";
            Tb_ConnectionStatus.BackColor = Color.Red;
            Tb_ConnectionStatus.ForeColor = Color.White;
            return;

        case 16:
            Tb_ConnectionStatus.Text = "Protocol Error";
            Tb_ConnectionStatus.BackColor = Color.Red;
            Tb_ConnectionStatus.ForeColor = Color.White;
            return;

        case 17:
            Tb_ConnectionStatus.Text = "Gateway Session Already Established";
            Tb_ConnectionStatus.BackColor = Color.Yellow;
            Tb_ConnectionStatus.ForeColor = Color.Black;
            return;

        case 32:
            Tb_ConnectionStatus.Text = "Operation Execution Failed";
            Tb_ConnectionStatus.BackColor = Color.Red;
            Tb_ConnectionStatus.ForeColor = Color.White;
            return;

        case 34:
            Tb_ConnectionStatus.Text = "Operation Not Available";
            Tb_ConnectionStatus.BackColor = Color.Red;
            Tb_ConnectionStatus.ForeColor = Color.White;
            return;

        case 36:
            Tb_ConnectionStatus.Text = "Unable to New Connection";
            Tb_ConnectionStatus.BackColor = Color.Red;
            Tb_ConnectionStatus.ForeColor = Color.White;
            return;

        case 38:
            Tb_ConnectionStatus.Text = "Panel ID Does Not Match";
            Tb_ConnectionStatus.BackColor = Color.Red;
            Tb_ConnectionStatus.ForeColor = Color.White;
            return;

        case 39:
            Tb_ConnectionStatus.Text = "Login Timeout";
            Tb_ConnectionStatus.BackColor = Color.Red;
            Tb_ConnectionStatus.ForeColor = Color.White;
            return;

        case 40:
            Tb_ConnectionStatus.Text = "Invalid Password";
            Tb_ConnectionStatus.BackColor = Color.Red;
            Tb_ConnectionStatus.ForeColor = Color.White;
            return;

        case 61:
            Tb_ConnectionStatus.Text = "Firmware Versiyon Not Compatible";
            Tb_ConnectionStatus.BackColor = Color.Red;
            Tb_ConnectionStatus.ForeColor = Color.White;
            return;
    }

CodePudding user response：

I'm pretty convinced your problem is in the first parameter ...EEC_FP10_ConnectTCPIP(char strIP...

I didn't find this library so I am not sure what's the native descriptor of this function but I'm guessing it expects a pointer to a string, not a char value. Double check that and refer to https://learn.microsoft.com/en-us/dotnet/framework/interop/default-marshalling-for-strings