FileStream类/StreamWriter类/StreamReader的使用

为了使条理清晰明了,以下为二个类来写: 

第一个类[方法类]:
/// <summary>
    /// 文件夹类[Directory]/文件类[File]
    /// FileStream类/StreamWriter类/StreamReader的使用
    /// </summary>
    class Method
    { 
        /// <summary>
        /// 创建文件夹的方法
        /// </summary>
        public string creatFold(string foldPath)
        {
            //创建文件夹
            Directory.CreateDirectory(foldPath);

            Console.WriteLine("创建文件夹成功了");
            Console.ReadLine();

            return foldPath;
        }

        /// <summary>
        /// 创建文件方法
        /// </summary>
        //public void creatFile(string filePath)
        //{
        //    //创建文件
        //    File.Create(filePath);
           
        //    Console.WriteLine("创建文件成功");
        //    Console.ReadLine();

        //    return;
        //}

       
        /// <summary>
        /// 判断文件是否存在
        /// </summary>
        /// <param name="isfile"></param>
        /// <returns></returns>
        public bool isFile(bool isfile, string filePath)
        {
            //以路径为参数构建FileInfo对象,用于检测文件相关信息
            FileInfo myFileInfo = new FileInfo(filePath);

            if (myFileInfo.Exists)
            {
                isfile = true;
            }
            else
            {
                isfile = false;
            }

            return isfile;
        }

        /// <summary>
        /// 检查文件夹是否存在
        /// </summary>
        /// <param name="isfold"></param>
        /// <returns></returns>
        public bool isFold(bool isfold,string foldPath)
        {
            //以路径为参数构建DirectoryInfo对象,用于检测文件夹相关信息
            DirectoryInfo myDirectoryInfo = new DirectoryInfo(foldPath);

            if (myDirectoryInfo.Exists)
            {
                isfold = true;
            }
            else
            {
                isfold = false;
            }

            return isfold;
        }

        /// <summary>
        /// 向文件中写入内容
        /// </summary>
        /// <param name="fs"></param>
        /// <param name="value"></param>
        private static void AddText(FileStream fs, string value)
        {
            byte[] info = new UTF8Encoding(true).GetBytes(value);
            fs.Write(info, 0, info.Length);           
        }
        /// <summary>
        /// 向文件中写入内容
        /// </summary>
        public void WriteFileInfo(string path)
        {
            try
            {
                //创建FileStream对象
                FileStream myWriteFileStr = File.Open(path, FileMode.OpenOrCreate);
                AddText(myWriteFileStr, "OH,My God!");
                AddText(myWriteFileStr, "/n我竟然被写入了文件中!");
                AddText(myWriteFileStr, "/n这太神奇了!/n");
                myWriteFileStr.Close();               
            }
            catch (IOException ex)
            {
                Console.WriteLine("写入时出错啦!");
                Console.WriteLine(ex.Message);
                Console.ReadLine();
                return;
            }

            Console.WriteLine("写入文件成功了!一起来庆祝一下吧!");
            Console.ReadLine();
        }

        /// <summary>
        /// 向文件中添加新的内容
        /// </summary>
        /// <param name="path"></param>
        public void AddAgainText(string path)
        {
            try
            {
                //在原有文件中添加内容
                StreamWriter myStrWrite = new StreamWriter(path, true);
                myStrWrite.WriteLine("Hello,我新来的,请大家多多关照!");
                myStrWrite.Close();
            }
            catch (IOException ex)
            {
                Console.WriteLine("写入时出错啦!");
                Console.WriteLine(ex.Message);
                Console.ReadLine();
                return;
            }

            Console.WriteLine("向文件中添加新的内容成功了!我太兴奋了!");
            Console.ReadLine();
        }

        /// <summary>
        /// 读出文件中的内容方法1
        /// </summary>
        /// <param name="filePath"></param>
        public void ReadFileInfo(string filePath)
        {
            try
            {
                FileStream myReadFileStr = File.OpenRead(filePath);
                byte[] b = new byte[1024];
                UTF8Encoding temp = new UTF8Encoding(true);

                Console.WriteLine("/n文件中的内容为[方法1]:");
                while (myReadFileStr.Read(b, 0, b.Length) > 0)
                {
                    Console.WriteLine(temp.GetString(b));
                }              
                myReadFileStr.Close();
            }
            catch (IOException ex)
            {
                Console.WriteLine("读出文件内容时出错了!");
                Console.WriteLine(ex.Message);
                Console.ReadLine();
            }

            Console.ReadLine();
        }

        /// <summary>
        /// 读出文件中的内容方法2
        /// </summary>
        /// <param name="filePath"></param>
        public void ReadStreamFile(string filePath)
        {
            try
            {
                StreamReader mySR = new StreamReader(filePath);
                Console.WriteLine("/n文件中的内容为[方法2]:");
                Console.WriteLine(mySR.ReadToEnd());               
                mySR.Close();
            }
            catch(IOException ex)
            {
                Console.WriteLine("读出文件内容时出错了!");
                Console.WriteLine(ex.Message);
                Console.ReadLine();
            }

            Console.ReadLine();
        }

        /// <summary>
        /// 输出文件相关信息
        /// </summary>
        /// <param name="fileFoldInfos"></param>
        public void FileFoldInfos(string fileFoldInfos)
        {
            //以路径为参数构建FileInfo对象,用于检测文件相关信息
            FileInfo myFileInfo = new FileInfo(fileFoldInfos);
            //输出文件相关信息
            Console.WriteLine("文件的相关信息如下:");
            Console.WriteLine("文件的父目录:" + myFileInfo.Directory);
            Console.WriteLine("文件创建的日期:" + myFileInfo.CreationTime);
            Console.WriteLine("文件所在目录的完整路径:" + myFileInfo.DirectoryName);
            Console.WriteLine("文件的完整目录:" + myFileInfo.FullName);
            Console.WriteLine("文件的扩展名:" + myFileInfo.Extension);
            Console.WriteLine("文件大小:" + myFileInfo.Length);
            Console.WriteLine("文件名:" + myFileInfo.Name);          
        }
    }

    /// <summary>
    /// 文件夹及文件路径类
    /// </summary>
    class FileFoldDir
    {
        /// <summary>
        /// 文件夹要创建的绝对路径字段
        /// </summary>
        private string myFoldPath =string.Empty;
        /// <summary>
        /// 文件夹要创建的绝对路径属性
        /// </summary>
        public string MyFoldPath
        {
            get
            {
                return myFoldPath;
            }
            set
            {
                myFoldPath = value;
            }
        }

        /// <summary>
        /// 文件创建的绝对路径字段
        /// </summary>
        private string myFilePath =string.Empty;
        /// <summary>
        /// 文件夹要创建的绝对路径属性
        /// </summary>
        public string MyFilePath
        {
            get
            {
                return myFilePath;
            }
            set
            {
                myFilePath = value;
            }
        }
    }

第二个类[主类]:
class FileFold
    {      
        static void Main(string[] args)
        {
            //定义isExist,用于判断文件夹或文件是否存在
            bool isExist = false;

            //定义一个FileFoldDir对象,用于设置文件夹及文件的绝对路径
            FileFoldDir myFileFoldDir = new FileFoldDir();
            //设置文件夹及文件的绝对路径
            myFileFoldDir.MyFoldPath = @"F:/files";
            myFileFoldDir.MyFilePath = @"F:/files/myfile.txt";

            //实例化一个Method对象
            Method myMethod = new Method();

            if (myMethod.isFile(isExist, myFileFoldDir.MyFilePath))
            {
                //输出文件的相关信息
                myMethod.FileFoldInfos(myFileFoldDir.MyFilePath);
                //读出文件内容[方法1]
                myMethod.ReadFileInfo(myFileFoldDir.MyFilePath);
               
                //再加入新的内容
                myMethod.AddAgainText(myFileFoldDir.MyFilePath);
                //输出文件的相关信息
                myMethod.FileFoldInfos(myFileFoldDir.MyFilePath);
                //读出文件内容[方法2]
                myMethod.ReadStreamFile(myFileFoldDir.MyFilePath);
            }
            else
            {
                //判断文件夹是否存在
                if (myMethod.isFold(isExist, myFileFoldDir.MyFoldPath))
                {
                    //如文件存在,则写入内容;否则创建文件,再写入内容
                    myMethod.WriteFileInfo(myFileFoldDir.MyFilePath);

                    //输出文件的相关信息
                    myMethod.FileFoldInfos(myFileFoldDir.MyFilePath);
                    //读出文件内容[方法1]
                    myMethod.ReadFileInfo(myFileFoldDir.MyFilePath);

                    //再加入新的内容
                    myMethod.AddAgainText(myFileFoldDir.MyFilePath);
                    //输出文件的相关信息
                    myMethod.FileFoldInfos(myFileFoldDir.MyFilePath);
                    //读出文件内容[方法2]
                    myMethod.ReadStreamFile(myFileFoldDir.MyFilePath);
                }
                else
                {
                    //创建文件夹
                    myMethod.creatFold(myFileFoldDir.MyFoldPath);
                    //创建文件,并写入内容
                    myMethod.WriteFileInfo(myFileFoldDir.MyFilePath);

                    //输出文件的相关信息
                    myMethod.FileFoldInfos(myFileFoldDir.MyFilePath);
                    //读出文件内容[方法1]
                    myMethod.ReadFileInfo(myFileFoldDir.MyFilePath);

                    //再加入新的内容
                    myMethod.AddAgainText(myFileFoldDir.MyFilePath);
                    //输出文件的相关信息
                    myMethod.FileFoldInfos(myFileFoldDir.MyFilePath);
                    //读出文件内容[方法2]
                    myMethod.ReadStreamFile(myFileFoldDir.MyFilePath);
                }
            }
        }
    }

最后别忘记了引用以下命名空间:
using System;
using System.Collections.Generic;
using System.Text;
using System.IO;