Question

I’ve been tasked with converting some legacy code to a new system and we’ve got some VB6 structures that are here. Is there a way to convert them into a C# structure easily?

I could redefine the structure in C# but there’s no fixed strings in C#. (Or maybe I misunderstand)

Any prods in the right direction?

Private Type MapRec
    Name As String * NAME_LENGTH
    Revision As Long
    Moral As Byte
    Up As Integer
    Down As Integer
    Left As Integer
    Right As Integer
    Music As String
    BootMap As Integer
    BootX As Byte
    BootY As Byte
    Tile() As TileRec
    Npc(1 To MAX_MAP_NPCS) As Integer
    NpcSpawn(1 To MAX_MAP_NPCS) As SpawnRec
    TileSet As Integer
    Region As Byte
End Type

Answer 1

With respect to fixed-length strings, yikes. It ain’t gonna happen because there is no equivalent construct. Unless Jon Skeet or Anders Hejlsberg know differently and can be invoked to weigh in — I don’t think even they know a way, cuz there ain’t one, I am pretty certain.

On the other hand, fixed-length strings are absolutely Satanic. Which is why they didn’t include them in .NET. 🙂

If you were to ask me how I would convert the above MapRec object to something usable in C#, well you kind of have your choice between a struct and a class. Personally, I dislike structs. If you used a class, then you could implement a kind of bastardized fixed-string by way of your setters and getters. As seen in this example, which is how I would implement your Type MapRec:

public class MapRec
{
    private const int MAX_MAP_NPCS = 25;
    private int fixedLength1 = 10;
    private string _name;

    public string Name
    {
        get
        {
            return _name;
        }
        set
        {
            if (value.Length != fixedLength1)
            {
                if (value.Length < fixedLength1)
                {
                    _name = value.PadRight(fixedLength1);
                }
                else
                {
                    _name = value.Substring(0,fixedLength1);
                    // or alternatively throw an exception if 
                    // a 11+ length string comes in
                }
            }
            else
            {
                _name = value;
            }
        }
    }

    // Constructor
    public MapRec()
    {
        Npc = new int[MAX_MAP_NPCS];
        NpcSpawn = new SpawnRec[MAX_MAP_NPCS];
    }

    public long Revision { get; set; }
    public byte Moral { get; set; }
    public int Up { get; set; }
    public int Down { get; set; }
    public int Left { get; set; }
    public int Right { get; set; }
    public string Music { get; set; }
    public int BootMap { get; set; }
    public byte BootX { get; set; }
    public byte BootY { get; set; }
    public TileRec[] Tile { get; set; }
    public int[] Npc { get; set; }
    public SpawnRec[] NpcSpawn { get; set; }
    public int TileSet { get; set; }
    public byte Region { get; set; }
}

In the end, unless one actually needs a fixed-length string (and perhaps Microsoft.VisualBasic.VBFixedStringAttribute could do the job), I would suggest staying the heck away from them.