C#FileStream复制大文件

即每次复制文件的一小段，以节省总内存开销。当然，本机复制也可以采用.NET内部的System.IO.File.Copy方法。

/// <summary>

/// 复制文件

/// </summary>

/// <param name="fromFile">要复制的文件</param>

/// <param name="toFile">要保存的位置</param>

/// <param name="lengthEachTime">每次复制的长度</param>

private void CopyFile(string fromFile, string toFile, int lengthEachTime)

{

FileStream fileToCopy = new FileStream(fromFile, FileMode.Open, FileAccess.Read);

FileStream copyToFile = new FileStream(toFile, FileMode.Append, FileAccess.Write);

int lengthToCopy;

if (lengthEachTime < fileToCopy.Length)//如果分段拷贝，即每次拷贝内容小于文件总长度

{

byte[] buffer = new byte[lengthEachTime];

int copied = 0;

while (copied <= ((int)fileToCopy.Length - lengthEachTime))//拷贝主体部分

{

lengthToCopy = fileToCopy.Read(buffer, 0, lengthEachTime);

fileToCopy.Flush();

copyToFile.Write(buffer, 0, lengthEachTime);

copyToFile.Flush();

copyToFile.Position = fileToCopy.Position;

copied += lengthToCopy;

}

int left = (int)fileToCopy.Length - copied;//拷贝剩余部分

lengthToCopy = fileToCopy.Read(buffer, 0, left);

fileToCopy.Flush();

copyToFile.Write(buffer, 0, left);

copyToFile.Flush();

}

else//如果整体拷贝，即每次拷贝内容大于文件总长度

{

byte[] buffer = new byte[fileToCopy.Length];

fileToCopy.Read(buffer,0,(int)fileToCopy.Length);

fileToCopy.Flush();

copyToFile.Write(buffer, 0, (int)fileToCopy.Length);

copyToFile.Flush();

}

fileToCopy.Close();

copyToFile.Close();

}