How to best convert VB6 "Select Case 1067 To 2938..." to C#?

Question

I'm converting some VB6 logic to C# and have encountered the following SELECT/CASE statement.

Select Case ZipCode
Case 1067 To 19417, 35075 To 35085, 48455 To 48465, 55583 To 55596, 67480 To 67551, 75392, 85126, _
    93047 To 93059, 21217 To 21739, 35091 To 35096, 48480, 55606 To 55779, 67655 To 67707, 76726 To 76835, _
    85221 To 87679, 94315 To 94419, 22844 To 25799, 35102, 48488, 56154 To 56254, 67731 To 67759, 76855 To 76889, _
    87719 To 88339, 94428 To 94437, 25868, 35112, 48499 To 48531, 56271, 67824 To 67829, 77761, 88353, 94522, _
    25879, 35117, 48653, 56281 To 56299, 69427 To 69429, 77773 To 77776, 88361 To 88364, 94553, 26121 To 26160, _
    35216 To 35282, 48720 To 48727, 56321 To 56337, 69437 To 69439, 78048 To 78126, 88368 To 88379, 94559, _
    26180 To 26215, 35287 To 35469, 49124 To 49356, 56410 To 56479, 70173 To 71287, 78136 To 79117, 88410, 95028 To 95032, _
    26316 To 26389, 35576 To 35768, 49406, 56575, 71332 To 71540, 80331 To 83313, 88481, 95111 To 95152, _
    26419, 36110, 49419, 56626 To 56648, 71546 To 71711, 83324 To 83362, 88529, 95176 To 95185, _
    26434 To 26441, 36304 To 36358, 49448, 56727 To 56745, 71720 To 72189, 83365 To 83379, 88633, 95188 To 95194, _
    26452, 36367 To 36369, 49453, 56751 To 57339, 72250 To 72417, 83413, 88662 To 90491, 95197

The best conversion I can think of is a series of if/then/else statements which map each range, e.g.

if((ZipCode >= 1067 && ZipCode <=19417) ||
   (ZipCode >= 35075 && ZipCode <=35085) ||
   ...

Or is there a better way, e.g. some way to put these range values in a hash/array/collection of some sort?

Answer 1

Assuming you are using 3.5 or above, and have access to extension methods:

If I had that many comparisons I would create a nice method for myself:

public static class IntUtils
{
    public static bool InRange(this int value, int low, int high)
    {
        return value <= low && value <= high;
    }
}

Then to use it:

if (zipCode.InRange(1067, 19417) ||
    zipCode.InRange(35075, 35085) || ...

If you don't have 3.5 or you don't want to use extension methods:

public static class IntUtils
{
    public static bool InRange(int value, int low, int high)
    {
        return value <= low && value <= high;
    }
}

then to use it:

if (IntUtils.InRange(zipCode, 1067, 19417) ||
    IntUtils.InRange(zipCode, 35075, 35085) || ...

Answer 2

Maybe you can create extension method on int like:

private static bool Between (this int i, int lower, int upper)
{
  return i >= lower && i <= upper;
}

and use it in code like

if ZipCode.Between(1067, 19417) || ZipCode.Between(35075, 35085) || ...

additional thoughts

If you do processing based on this, maybe you can use something along those lines

Dictionary<int[], Action> actionMap = new Dictionary<int[], Action>
{
  {new[]{1067,19417}, ProcessA},
  {new[]{35075, 35085}, ProcessB}
};

public void ProcessA()
{
  // do something;
}

public void ProcessB()
{
  // do something else;
}

public void Process(int zipCode)
{
  var action = actionMap.FirstOrDefault(a => zipCode >= a.Key[0] && zipCode <= a.Key[1]);
  if (action.Value != null)
  {
     action.Value();
  }
}

p.s. Not sure this is 100% working code, wrote it from top of my head p.p.s. Triead and now I'm quite sure it's working

Answer 3

The method you describe is the literal transformation from VB to C#. However, this is so much data that it seems better off in a configuration file than in the code. If you do that, the easiest way is probably to simply loop through the list with zipcodes and compare them one by one.

A more efficient way would be to sort the zipcodes and do a binary search, or use a hash function or something like that, but I would be surprised if this turns out to be a performance bottleneck.

Answer 4

If you wanted to make some of the given approaches a little more abstract, you could go with an extension method like such:

public static class Utils
{
    public static bool InRange<T>(this T value, T low, T high) where T : IComparable
    {
        return low.CompareTo(value) <= 0 && high.CompareTo(value) >= 0;
    }
}