Question

As I am trying to code a C# application from an existing application but developed in Delphi,
Very tough but managed some how till, but now I have come across a problem…

Delphi code contains following code:

type  
  TFruit = record
    name : string[20];
    case isRound : Boolean of // Choose how to map the next section
      True  :
        (diameter : Single);  // Maps to same storage as length
      False :
        (length   : Single;   // Maps to same storage as diameter
         width    : Single);
  end;

i.e. a variant record (with case statement inside) and accordingly record is constructed and its size too.
On the other hand I am trying to do the same in C# struct, and haven’t succeeded yet, I hope somemone can help me here.
So just let me know if there’s any way I can implement this in C#.
Thanks in advance….

Answer 1

You could use an explicit struct layout to replicate this Delphi variant record. However, I would not bother since it seems pretty unlikely that you really want assignment to diameter to assign also to length, and vice versa. That Delphi record declaration looks like it dates from mid-1990s style of Delphi coding. Modern Delphi code would seldom be written that way.

I would just do it like this:

struct Fruit
{
    string name;
    bool isRound;
    float diameter; // only valid when isRound is true
    float length;   // only valid when isRound is false
    float width;    // only valid when isRound is false
}

A more elegant option would be a class with properties for each struct field. And you would arrange that the property getters and setters for the 3 floats raised exceptions if they were accessed for an invalid value of isRound.