火狐浏览器下载文件中文乱码，文件名中的空格变加号("+")的问题

解决一下问题：

1、火狐浏览器下载文件，中文变乱码

2、IE浏览器下载文件，丢失文件扩展名或强制扩展名为".txt"

3、浏览器下载文件，文件名中的空格变成加号("+")，测试过程中chrome,firefox,ie均出现此问题

参考https://stackoverflow.com/questions/93551/how-to-encode-the-filename-parameter-of-content-disposition-header-in-http

string fileFullName = @"D:\新建 Microsoft Word 文档.docx"; //文件绝对路径
string fileName = Path.GetFileName(fileFullName);
using (FileStream stream = new FileStream(fileFullName, FileMode.Open, FileAccess.Read, FileShare.Read))
{
    //指定块大小  
    long chunkSize = 102400;
    //建立一个100K的缓冲区  
    byte[] buffer = new byte[chunkSize];
    //未读的字节数  
    long dataToRead = stream.Length;

    //添加Http头  
    string contentDisposition;
    if (Request.Browser.Browser == "IE" && (Request.Browser.Version == "7.0" || Request.Browser.Version == "8.0"))
    {
        contentDisposition = "attachment;filename=" + Uri.EscapeDataString(fileName);
    }
    else if (Request.Browser.Browser == "Safari")
    {
        contentDisposition = "attachment;filename=" + fileName;
    }
    else
    {
        contentDisposition = "attachment;filename*=UTF-8''" + Uri.EscapeDataString(fileName);
    }
    //Response.AddHeader("Content-Disposition", contentDisposition);

    HttpContext.Current.Response.ContentType = "application/octet-stream";
    HttpContext.Current.Response.AddHeader("Content-Disposition", contentDisposition);
    HttpContext.Current.Response.AddHeader("Content-Length", dataToRead.ToString());

    while (dataToRead > 0 && HttpContext.Current.Response.IsClientConnected)
    {
        int length = stream.Read(buffer, 0, (int)chunkSize);
        HttpContext.Current.Response.BinaryWrite(buffer);
        HttpContext.Current.Response.Flush();
        HttpContext.Current.Response.Clear();

        dataToRead -= length;
    }
    HttpContext.Current.Response.Close();
}