gistfile1.txt

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            // Count up from 1 to 100.
            for (int i = 1; i <= 100; i++)
            {
                // If a number is not a multiple of 3 or 5, print it.
                if (((i % 3) != 0) && ((i % 5) != 0))
                {
                    Console.Write(i);
                }
                else
                {
                    // If a number is a multiple of 3 print "Fizz"
                    if ((i % 3) == 0)
                    {
                        Console.Write("Fizz");
                    }
                    // If a number is a multiple of 5 print "Buzz"
                    if((i % 5) == 0)
                    {
                        Console.Write("Buzz");
                    }
                }
                // Print a new line between numbers.
                Console.WriteLine("");
            }
        }
    }
}

This is not a valid C# program. Neither i%3 nor i%5 evaluate to boolean expressions.
Also, seems like your program would actually print the opposite of the requirements of the FizzBuzz spec if you fix the syntax errors.

Nice catch on the syntax error. I didn't realize C# was different than C in evaluating integers as bool's. As far as meeting the fizzbuzz spec though, as far as I can tell it is correct. =/