Summary:

The DCB structure defines the control setting for a serial communications device.

C# Definition:

using System.Collections.Specialized;
using System.Runtime.InteropServices;

[StructLayout(LayoutKind.Sequential)]
internal struct Dcb
{
    internal uint DCBLength;
    internal uint BaudRate;
    private BitVector32 Flags;

    private ushort wReserved;        // not currently used
    internal ushort XonLim;           // transmit XON threshold
    internal ushort XoffLim;          // transmit XOFF threshold             

    internal byte ByteSize;
    internal Parity Parity;
    internal StopBits StopBits;

    internal sbyte XonChar;          // Tx and Rx XON character
    internal sbyte XoffChar;         // Tx and Rx XOFF character
    internal sbyte ErrorChar;        // error replacement character
    internal sbyte EofChar;          // end of input character
    internal sbyte EvtChar;          // received event character
    private ushort wReserved1;       // reserved; do not use     

    private static readonly int fBinary;
    private static readonly int fParity;
    private static readonly int fOutxCtsFlow;
    private static readonly int fOutxDsrFlow;
    private static readonly BitVector32.Section fDtrControl;
    private static readonly int fDsrSensitivity;
    private static readonly int fTXContinueOnXoff;
    private static readonly int fOutX;
    private static readonly int fInX;
    private static readonly int fErrorChar;
    private static readonly int fNull;
    private static readonly BitVector32.Section fRtsControl;
    private static readonly int fAbortOnError;

    static Dcb()
    {
        // Create Boolean Mask
        int previousMask;
        fBinary = BitVector32.CreateMask();
        fParity = BitVector32.CreateMask(fBinary);
        fOutxCtsFlow = BitVector32.CreateMask(fParity);
        fOutxDsrFlow = BitVector32.CreateMask(fOutxCtsFlow);
        previousMask = BitVector32.CreateMask(fOutxDsrFlow);
        previousMask = BitVector32.CreateMask(previousMask);
        fDsrSensitivity = BitVector32.CreateMask(previousMask);
        fTXContinueOnXoff = BitVector32.CreateMask(fDsrSensitivity);
        fOutX = BitVector32.CreateMask(fTXContinueOnXoff);
        fInX = BitVector32.CreateMask(fOutX);
        fErrorChar = BitVector32.CreateMask(fInX);
        fNull = BitVector32.CreateMask(fErrorChar);
        previousMask = BitVector32.CreateMask(fNull);
        previousMask = BitVector32.CreateMask(previousMask);
        fAbortOnError = BitVector32.CreateMask(previousMask);

        // Create section Mask
        BitVector32.Section previousSection;
        previousSection = BitVector32.CreateSection(1);
        previousSection = BitVector32.CreateSection(1, previousSection);
        previousSection = BitVector32.CreateSection(1, previousSection);
        previousSection = BitVector32.CreateSection(1, previousSection);
        fDtrControl = BitVector32.CreateSection(2, previousSection);
        previousSection = BitVector32.CreateSection(1, fDtrControl);
        previousSection = BitVector32.CreateSection(1, previousSection);
        previousSection = BitVector32.CreateSection(1, previousSection);
        previousSection = BitVector32.CreateSection(1, previousSection);
        previousSection = BitVector32.CreateSection(1, previousSection);
        previousSection = BitVector32.CreateSection(1, previousSection);
        fRtsControl = BitVector32.CreateSection(3, previousSection);
        previousSection = BitVector32.CreateSection(1, fRtsControl);
    }

    public bool Binary
    {
        get { return Flags[fBinary]; }
        set { Flags[fBinary] = value; }
    }

    public bool CheckParity
    {
        get { return Flags[fParity]; }
        set { Flags[fParity] = value; }
    }

    public bool OutxCtsFlow
    {
        get { return Flags[fOutxCtsFlow]; }
        set { Flags[fOutxCtsFlow] = value; }
    }

    public bool OutxDsrFlow
    {
        get { return Flags[fOutxDsrFlow]; }
        set { Flags[fOutxDsrFlow]  = value; }
    }

    public DtrControl DtrControl
    {
        get { return (DtrControl)Flags[fDtrControl]; }
        set { Flags[fDtrControl] = (int)value; }
    }

    public bool DsrSensitivity
    {
        get { return Flags[fDsrSensitivity]; }
        set { Flags[fDsrSensitivity] = value; }
    }

    public bool TxContinueOnXoff
    {
        get { return Flags[fTXContinueOnXoff]; }
        set { Flags[fTXContinueOnXoff] = value; }
    }

    public bool OutX
    {
        get { return Flags[fOutX]; }
        set { Flags[fOutX] = value; }
    }

    public bool InX
    {
        get { return Flags[fInX]; }
        set { Flags[fInX] = value; }
    }

    public bool ReplaceErrorChar
    {
        get { return Flags[fErrorChar]; }
        set { Flags[fErrorChar] = value; }
    }

    public bool Null
    {
        get { return Flags[fNull]; }
        set { Flags[fNull] = value; }
    }

    public RtsControl RtsControl
    {
        get { return (RtsControl)Flags[fRtsControl]; }
        set { Flags[fRtsControl]  = (int)value; }
    }

    public bool AbortOnError
    {
        get { return Flags[fAbortOnError]; }
        set { Flags[fAbortOnError] = value; }
    }
}

User-Defined Field Types:

public enum Parity : byte
{
    None = 0,
    Odd = 1,
    Even = 2,
    Mark = 3,
    Space = 4,
}

public enum StopBits : byte
{
    One = 0,
    OnePointFive = 1,
    Two = 2
}

See also DtrControl and RtsControl

VB Definition:

Private Type DCB
    DCBlength As Long
    BaudRate As Long
    fBitFields As Long 'See Comments in Win32API.Txt
    wReserved As Integer
    XonLim As Integer
    XoffLim As Integer
    ByteSize As Byte
    Parity As Byte
    StopBits As Byte
    XonChar As Byte
    XoffChar As Byte
    ErrorChar As Byte
    EofChar As Byte
    EvtChar As Byte
    wReserved1 As Integer 'Reserved; Do Not Use
End Type

VB.Net Definition

Note there is a Microsoft KB Artcile describing how to access serial and parallel ports in VB.NET

http://support.microsoft.com/default.aspx?scid=kb;en-us;823179&Product=vb6

Here is the structure - worked for me:

  Public Structure DCB
    Public DCBlength As Int32
    Public BaudRate As Int32
    Public fBitFields As Int32
    Public wReserved As Int16
    Public XonLim As Int16
    Public XoffLim As Int16
    Public ByteSize As Byte
    Public Parity As Byte
    Public StopBits As Byte
    Public XonChar As Byte
    Public XoffChar As Byte
    Public ErrorChar As Byte
    Public EofChar As Byte
    Public EvtChar As Byte
    Public wReserved1 As Int16 'Reserved; Do Not Use
  End Structure

Notes:

Special thanks to Jay's Outlook MVP from Visual C# Community for the guidance.

fDtrControl = BitVector32.CreateSection(2, previousSection);

fRtsControl = BitVector32.CreateSection(3, previousSection);

You will notice that fDtrControl expects 2 and fRtsControl expect 3. Why?

The reason is that the highest value within enum DtrControl is 2, and highest valye within enum RtsControl is 3.

This helps you to fix the bitflag issue in c to c#. I had tested it and it works greatly.

To use this code,

Example:

C#

Dcb myDcb = new Dcb();

myDcb.Binary = true;

myDcb.DtrControl = DtrControl.Disable; // DtrControl is an enum

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