How to manipulate data in packed structures using a proxy class?

Question

Hello all.

i have a project wherein i am using System.Runtime.InteropServices to define a struct in the following manner such that it is packed to byte boundaries and ready to send to a serial port and from there to an embedded system. (business sensitive names have been removed)

public class ControlCommandClass 
{
  [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
  public struct ControlCommandData
  {
    public Uint32 Field1;
    public Uint16 Field2;
    public Sbyte  Field3;
    public Uint32 Field4;
  }; // this struct is 11 bytes in memory!

  private ControlCommandData rawdata;

  public UTCTime Field1;

  public ControlCommandClass()
  {
    this.Field1 = new UTCTime(ref this.rawdata.Field1);
  }
}

What i am trying to do is to do is to use the constructor to assign references to those fields to a proxy class using

Field1 = new UTCTime(ref this.rawdata.Field1)

to wrap the raw data in the structure to a class which allows more advanced operations before calculating the 32 bit integer which corresponds to the time. my proxy class is

public class UTCTime : Field
{
  private Uint32 dataReference;

  public UTCTime(ref rawData)
  {
    // code to do reference assignment here?
  }
}

Is there any way to have dataReference as a reference to Field1 such that my proxy class is able to manipulate the data in the packed structure?

Thanks in advance, Thomas.

Answer 1

That is not possible as is.

General rule of thumb is that you cannot store a reference to a managed object.

Passing by reference allows you to use a reference as much as you want. But you'd have to switched to an unsafe block with IntPtr's to accomplish what you're trying to do.