Handle Read and write access

Cystring.class.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Text.RegularExpressions;

namespace Cylib {
    /**
     * @class Cyfile
     * @name Cyfile
     * @desc Read and write a file
     * @author Sven Gehring
     * @copyright 2014+ Sven Gehring
     */
    public class Cyfile {

        private string filepath;

        /**
         * @method Cyfile
         * @name Cyfile class cosntructor
         * @desc Set the file path for this file handler
         *  This will also check if the file exists
         * @param {string} filepath - The given file path
         */
        public Cyfile(string filepath){
            if (!File.Exists(filepath)) {
                MessageBox.Show("Invalid file path");
                return;
            }

            this.filepath = filepath;
        }
        
        
        /**
         * @method writeString
         * @name Write String
         * @alias 'schreiben'
         * @desc Write a string to the file
         * @param {string} input - The given input string
         */
        public void writeString(string input) {
            FileStream file = new FileStream(this.filepath, FileMode.Create);
            StreamWriter sw = new StreamWriter(file);

            sw.WriteLine(input);
            sw.Close();
            file.Close();
        }


        /**
         * @method readString
         * @name Read String
         * @alias 'lesen'
         * @desc Read a string from the file (whole file)
         * @return {string} data - The file content
         */
        public string readString() {
            FileStream file = new FileStream(this.filepath, FileMode.Open);
            StreamReader sr = new StreamReader(file);

            string data = "";
            while (sr.Peek() != -1) data += sr.ReadLine() + "\n";

            sr.Close();
            file.Close();

            return data;
        }
    }
}