读操作：

方法1：

string str = File.ReadAllText(@filepath, Encoding.Default);

方法2：

byte[] buffer = File.ReadAllBytes(@filepath);
string str = Encoding.Default.GetString(buffer);

方法3：

string[] buffer = File.ReadAllLines(@filepath,Encoding.Default);
string str = "" ;
foreach (var buf in buffer)
{
    str = str + buf +"\n";
}

方法4：

FileStream fsRead = new FileStream(@filepath, FileMode.OpenOrCreate);
byte[] buffer = new byte[1024 * 1024 * 5];
int length = fsRead.Read(buffer, 0, buffer.Length);
string str = Encoding.Default.GetString(buffer, 0, length);
fsRead.Close();
fsRead.Dispose();

方法5：

string str ="";
using (FileStream fsRead = new FileStream(@filepath,    FileMode.OpenOrCreate,Fileaccess.Read))
{
  byte[] buffer = new byte[1024 * 1024 * 5];
  int length = fsRead.Read(buffer, 0, buffer.Length);
  str = Encoding.Default.GetString(buffer, 0, length);
}

写操作：

方法1：

File.WriteAllText(@filepath, str, Encoding.Default);

方法2：

byte[] buffer = Encoding.Default.GetBytes(str);
File.WriteAllBytes(@filepath,buffer);

方法3：

File.WriteAllLines(@filepath, str.Split(' '),Encoding.Default);

方法4：

FileStream fsWrite = new FileStream(@filepath, FileMode.OpenOrCreate, FileAccess.Write);
byte[] buffer = Encoding.Default.GetBytes(str);
fsWrite.Write(buffer, 0, buffer.Length);
fsWrite.Close();
fsWrite.Dispose();

方法5:

byte[] buffer = Encoding.Default.GetBytes(str);
using (FileStream fsWrite = new FileStream(@filepath, FileMode.OpenOrCreate, FileAccess.Write))
{
  fsWrite.Write(buffer, 0, buffer.Length);
}

操作文件夹:

CreateDirectory：创建文件夹

Delete：删除文件夹

Move：剪切文件夹

Exist：判断是否存在

GetFiles：获得指定的目录下所有文件的全路径

GetDirectory：获得指定目录下所有文件夹的全路径