Program.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace reverseWords
{
    public class Program
    {
        static void Main(string[] args)
        {
            string inputFile;
            string outputFile;
            string processedData;

            inputFile = GetFilePath("Enter Input File: ");
            outputFile = GetFilePath("Enter Output File: ");

            processedData = ProcessFile(inputFile);
            WriteToFile(outputFile, processedData);
        }

        /// <summary>
        /// Prompts the user to enter a path to a file
        /// </summary>
        /// 
        /// <param name="message">The message that is displayed to the user</param>
        /// 
        /// <returns>A string containing the path to a file</returns>
        private static string GetFilePath(string message)
        {
            string filePath;

            do
            {
                Console.Write(message);
                filePath = Console.ReadLine();

            } while (filePath == null || filePath.Trim().Length == 0);

            return filePath;
        }

        /// <summary>
        /// Processes the input file
        /// </summary>
        /// 
        /// <param name="input">The input file that will be processed</param>
        /// 
        /// <returns>A string containing the output from processing the file</returns>
        private static string ProcessFile(string input)
        {
            string currentLine;
            StringBuilder stringBuilder = new StringBuilder();

            using( StreamReader reader = new StreamReader(input) )
            {
                currentLine = reader.ReadLine();

                //TODO: Possibly use WHILE instead of IF?
                if( currentLine != null )
                {
                    //TODO: Write logic to process the input file
                }

                reader.Close();
            }

            return stringBuilder.ToString();
        }

        /// <summary>
        /// Writes data to a file
        /// </summary>
        /// 
        /// <param name="outputFile">The output file to write to</param>
        /// <param name="words">The data that will be written to the file</param>
        private static void WriteToFile(string outputFile, string words)
        {
            using(StreamWriter writer = new StreamWriter(outputFile))
            {
                writer.Write(words);
                writer.Close();
            }
        }
    }
}