Question

用c#怎样从服务器下载文件，并保存为相应的类型

现在要通过http get方式从google docs下载文件。文件流已经可以得到了。但是我不知道怎么才能保存成正确的格式。比如一个doc文件，实际大小是85kb，我用streamwriter方法保存，却有140kb，而且用word也打不开。请问用什么方法才能将文件正确保存？
保存代码：
Stream drStream = dResponse.GetResponseStream();
Console.WriteLine(dResponse.ContentType.ToString());//这里得到的信息是application/msword;charset=utf-8
Encoding encode = System.Text.Encoding.GetEncoding("utf-8");
StreamReader drStreamReader = new StreamReader(drStream,encode);
FileStream fs = new FileStream("test2.doc", FileMode.Create);
StreamWriter sw = new StreamWriter(fs);
sw.Write(drStreamReader.ReadToEnd());
sw.Close();
fs.Close();

Answer 1

C#从服务器下载文件可以使用下面4个方法：TransmitFile、WriteFile、WriteFile和流方式下载文件，并保存为相应类型，方法如下：

1、TransmitFile实现下载

protected void Button1_Click(object sender, EventArgs e)
    {
        /* 
        微软为Response对象提供了一个新的方法TransmitFile来解决使用Response.BinaryWrite 
        下载超过400mb的文件时导致Aspnet_wp.exe进程回收而无法成功下载的问题。 
        代码如下： 
        */ 
        Response.ContentType = "application/x-zip-compressed";
        Response.AddHeader("Content-Disposition", "attachment;filename=z.zip");
        string filename = Server.MapPath("DownLoad/z.zip");
        Response.TransmitFile(filename);
    }

2、WriteFile实现下载

protected void Button2_Click(object sender, EventArgs e)
    {
        /* 
        using System.IO;

        */
        string fileName = "asd.txt";//客户端保存的文件名 
        string filePath = Server.MapPath("DownLoad/aaa.txt");//路径

        FileInfo fileInfo = new FileInfo(filePath);
        Response.Clear();
        Response.ClearContent();
        Response.ClearHeaders();
        Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
        Response.AddHeader("Content-Length", fileInfo.Length.ToString());
        Response.AddHeader("Content-Transfer-Encoding", "binary");
        Response.ContentType = "application/octet-stream";
        Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
        Response.WriteFile(fileInfo.FullName);
        Response.Flush();
        Response.End();
    }

3、WriteFile分块下载 

protected void Button3_Click(object sender, EventArgs e)
    {
        string fileName = "aaa.txt";//客户端保存的文件名 
        string filePath = Server.MapPath("DownLoad/aaa.txt");//路径

        System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);

        if (fileInfo.Exists == true)
        {
            const long ChunkSize = 102400;//100K 每次读取文件，只读取100K，这样可以缓解服务器的压力 
            byte[] buffer = new byte[ChunkSize];

            Response.Clear();
            System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);
            long dataLengthToRead = iStream.Length;//获取下载的文件总大小 
            Response.ContentType = "application/octet-stream";
            Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));
            while (dataLengthToRead > 0 && Response.IsClientConnected)
            {
                int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//读取的大小 
                Response.OutputStream.Write(buffer, 0, lengthRead);
                Response.Flush();
                dataLengthToRead = dataLengthToRead - lengthRead;
            }
            Response.Close();
        }
    }

4、流方式下载

protected void Button4_Click(object sender, EventArgs e)
    {
        string fileName = "aaa.txt";//客户端保存的文件名 
        string filePath = Server.MapPath("DownLoad/aaa.txt");//路径

        //以字符流的形式下载文件 
        FileStream fs = new FileStream(filePath, FileMode.Open);
        byte[] bytes = new byte[(int)fs.Length];
        fs.Read(bytes, 0, bytes.Length);
        fs.Close();
        Response.ContentType = "application/octet-stream";
        //通知浏览器下载文件而不是打开 
        Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
        Response.BinaryWrite(bytes);
        Response.Flush();
        Response.End();
    }

Answer 2

try
{
string savePath = ""//保存路劲
, downFileUrl = "";//下载文件链接地址
WebClient wcClient = new WebClient();
WebRequest webReq = WebRequest.Create(downFileUrl);
WebResponse webRes = webReq.GetResponse();
int fileLength = webRes.ContentLength;

Stream srm = webRes.GetResponseStream();
StreamReader srmReader = new StreamReader(srm);
byte[] bufferbyte = new byte[fileLength];
int allByte = (int)bufferbyte.Length;
int startByte = 0;
while (fileLength > 0)
{
//Application.DoEvents();
int downByte = srm.Read(bufferbyte, startByte, allByte);
if (downByte == 0) { break; };
startByte += downByte;
allByte -= downByte;
}

if (!File.Exists(savePath))
{
string[] dirArray = savePath.Split('\\');
string temp = string.Empty;
for (int i = 0; i < dirArray.Length - 1; i++)
{
temp += dirArray[i].Trim() + "\\";
if (!Directory.Exists(temp))
Directory.CreateDirectory(temp);
}
}
FileStream fs = new FileStream(savePath, FileMode.OpenOrCreate, FileAccess.Write);
fs.Write(bufferbyte, 0, bufferbyte.Length);
srm.Close();
srmReader.Close();
fs.Close();
}
catch (WebException ex)
{
throw ex;
}

用这段代码试试 我自己一直用这个代码下载的 貌似我当初测试的时候是用DOC测的

今天测试了下自己的代码 可以下DOC 我怀疑你的还是编码问题