FileStream对文本进行读写操作

class FileHelper
{

/// <summary>
/// 检验文件路径是否合法
/// </summary>
/// <param name="path">文件路径</param>
private static bool CheckPath(string path)
{
//正确格式：C:\Users\jcx\Desktop\Test.txt
string pattern = @"\w{1}:([\\].+)*.+\.\w{3,}";
Regex rg = new Regex(pattern);
return rg.IsMatch(path);
}

/// <summary>
/// 创建一个新的文本文件
/// </summary>
/// <param name="path">文件路径</param>
/// <param name="content">写入到文本的内容</param>
public static void CreateNewTxtFile(string path,string content)
{
if (!CheckPath(path))
{
throw new Exception("文件路径不合法");
}
//存在则删除
if (File.Exists(path))
{
File.Delete(path);
}

using (FileStream fs=new FileStream (path,FileMode.CreateNew,FileAccess.Write))
{
byte[] bt = Encoding.Default.GetBytes(content);
fs.Write(bt,0,bt.Length);

} //using
}

/// <summary>
/// 读取文本文件
/// </summary>
/// <param name="path">文件路径</param>
/// <param name="readByte">指定每次读取字节数</param>
/// <returns>读取的全部文本内容</returns>
public static string ReadTxtFile(string path,long readByte)
{
if (!CheckPath(path))
{
throw new Exception("文件路径不合法");
}

StringBuilder result = new StringBuilder();
using (FileStream fs=new FileStream (path,FileMode.Open,FileAccess.Read))
{
byte[] bt = new byte[readByte];

while (fs.Read(bt,0,bt.Length)>0) //每次只从文件中读取部分字节数，一点点读
{
string txt = Encoding.Default.GetString(bt);  //解码转换成字符串
result.AppendLine(txt);
}

} //using
return result.ToString();

}

}

class Program
{
static void Main(string[] args)
{

string path = @"C:\Users\jcx\Desktop\Test.txt";

FileHelper.CreateNewTxtFile(path, "好好努力");
string r = FileHelper.ReadTxtFile(path,2);      //2个字节为一个汉字，一个汉字一个汉字的读
Console.WriteLine(r);

} // Main

}