Fun with Expression Trees

I have just been looking through some old code, and found a classic method that most people will use at some point;

public static int CalculatePercentage(int done, int total)
{
     return (done * 100) / total;
}

Now,  I gots a thinking... Instead of using a method (or indeed a property) for this type of "expression", why not use the C# 3.0 Expression Tree functionality?  So just for a larf I came up with;

Expression<Func<int, int, int>> percentage = (done, totalCount) => ((done * 100) / totalCount);

The problem here is that in order to use the expression tree I have to call Compile() on the expression before invoking it. 

Expression<Func<int, int, int>> percentage = (done, totalCount) => ((done * 100) / totalCount);
var completed = percentage.Compile()(3, 15);

So in this case, I think using an Expression is a little overkill.  So I opted to have a static Func<> in a static class; (some may argue expressing this as a Func<T,K> rather than the original method may be overkill, but I think its cool ;) ). 

class SimpleFunctions
{
    public static readonly Func<int, int, int> CalculatePercentage = ((done, totalCount) => ((done * 100) / totalCount));
}

Again, its down to personal preference.  This is just an example of using the Func<> class instead of creating a method to do a specific job.  And working out a percentage isn't exactly a taxing calculation, but you get the idea ;). 

 

Full Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Samples.ExpressionTrees
{
    class Program
    {
        static void Main(string[] args)
        {
        
            int total = 15;
            for (int done = 0; done < total; done++)
            {
                Console.WriteLine(string.Format("{0} out of {1} done -- {2}% Complete", done, total, SimpleFunctions.CalculatePercentage(done, total)));
            }

        }
    }

    class SimpleFunctions
    {
        public static readonly Func<int, int, int> CalculatePercentage = ((done, totalCount) => ((done * 100) / totalCount));
    }
}

Output

Refrences

http://davidhayden.com/blog/dave/archive/2006/12/21/BuildExpressionTreesTutorialAndExamples.aspx