c#怎么实现下载FTP服务器中的某个文件

//可以通过这个来下载：
//当然filePath是FTP服务器上，存储文件的具体路径，如“H:\\Files\\UploadFile”
//fileName-是具体的文件名称
FileInfo DownloadFile = new FileInfo(filePath);

//----可以下载大附件
System.IO.Stream iStream = null;

// Buffer to read 10K bytes in chunk:
byte[] buffer = new Byte[10000];

// Length of the file:
int length;

// Total bytes to read:
long dataToRead;

try
{
// Open the file.
iStream = new System.IO.FileStream(filePath, System.IO.FileMode.Open,
System.IO.FileAccess.Read,System.IO.FileShare.Read);

// Total bytes to read:
dataToRead = iStream.Length;

Response.ContentType = "application/octet-stream; Charset=UTF8";
Response.AddHeader("Content-Disposition", "attachment; filename="+System.Web.HttpUtility.UrlEncode(fileName,System.Text.Encoding.UTF8));
// Response.AddHeader("Content-Disposition", "attachment; filename=" + fileName);

// Read the bytes.
while (dataToRead > 0)
{
// Verify that the client is connected.
if (Response.IsClientConnected)
{
// Read the data in buffer.
length = iStream.Read(buffer, 0, 10000);

// Write the data to the current output stream.
Response.OutputStream.Write(buffer, 0, length);

// Flush the data to the HTML output.
Response.Flush();

buffer= new Byte[10000];
dataToRead = dataToRead - length;
}
else
{
//prevent infinite loop if user disconnects
dataToRead = -1;
}
}
}
catch (Exception ex)
{
// Trap the error, if any.
Response.Clear();
Response.Write("");
Response.End();

}
finally
{
if (iStream != null)
{
//Close the file.
iStream.Close();
}
Response.Close();
}

不懂 太高深了