A quick response to https://gist.github.com/5640717.git in C#

Program.cs

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            var responses = new[]
            {
                new SurveyResponse 
                { 
                    Site = "site1", 
                    Results = {
                        {ProgrammingLanguage.CSharp, 3},
                        {ProgrammingLanguage.FSharp, 1},
                        {ProgrammingLanguage.Haskell, 0},
                    }
                },
                new SurveyResponse 
                { 
                    Site = "site2", 
                    Results = {
                        {ProgrammingLanguage.CSharp, 3},
                        {ProgrammingLanguage.Ruby, 5},
                    }
                },
                new SurveyResponse 
                { 
                    Site = "site3", 
                    Results = {
                        {ProgrammingLanguage.Ruby, 7},
                        {ProgrammingLanguage.JavaScript, 4},
                    }
                },
            };

            Console.WriteLine(SurveyToCsv(responses));
        }

        public static string SurveyToCsv(IEnumerable<SurveyResponse> responses)
        {
            return 
                "site," + String.Join(",", Enum.GetNames(typeof(ProgrammingLanguage))) + "\n"
                + String.Join("\n", 
                    responses.Select(response =>
                        response.Site + "," 
                        + String.Join(",", 
                            Enum.GetValues(typeof(ProgrammingLanguage))
                                .Cast<ProgrammingLanguage>()
                                .Select(p => (response.Results.ContainsKey(p) ? response.Results[p] : 0).ToString())
                                )));
        }
    }

    class SurveyResponse
    {
        public SurveyResponse()
        {
            Results = new Dictionary<ProgrammingLanguage, int>();
        }
        public string Site;
        public Dictionary<ProgrammingLanguage, int> Results;
    }

    enum ProgrammingLanguage
    {
        CSharp,
        FSharp,
        Haskell,
        Ruby,
        JavaScript
    }
}