Slightly Better Version

Last week I posted a function to convert an IP address to its decimal value using c#.

I have a mildly better approach, though by better, admittedly, I really just mean “I’m using some new stuff from the current version of c#”.

It occurred to me that in place of the anonymous delegate I could just as easily use a lambda expression, therefore we end up with this approach:

private static string IpToDecimal(string ipAddress)
{
   // split up the IP into octets and prep our string builder
   List<string> octets = new List<string>(ipAddress.Split('.'));
   long decIP = 0;
   int shift = 3;

   // loop through the octets and compute the decimal version
   octets.ForEach(octet => { decIP += long.Parse(octet) << (shift * 8); shift--; });
   return decIP.ToString();
}

Now, if you wanted to, you could really use var instead of List<string> and you could likely inline the initialization, but that ends up unreadable.

HOWEVER if you are adamant about using new things, like LINQ, lambda expressions and the language features of c# to convert this bad boy over, you can do it!

I just wouldn’t likely throw this code at the rookie…

private static string IpToDecimal2(string ipAddress)
{
   // need a shift counter
   int shift = 3;

   // split and loop through the octets
   var octets = ipAddress.Split('.').Select(p => long.Parse(p));
   return octets.Aggregate(0L, (total, octet) =>
       (total + (octet << (shift-- * 8)))).ToString();
}

This is actually cool because it’s really only three lines of code.  A couple of things to note:

1. Using LINQ we are able to parse out the string bits and convert the octets to longs with the Select method.



2. I’m using the Aggregate method and passing in a seed of 0, which I type with L so that the compiler doesn’t see it as an int.



3. total is used to keep the running track; octet is the parameter passed in from the octets collection.



4. shift is decremented each pass as we walk across the octets.