Asp.net实现附件下载（乱码解决）

    private void Page_Load(object sender, System.EventArgs e)
    {
        if (Request.QueryString["Recordid"] != null && Request.QueryString["Recordid"].ToString() != "")
        {
            StarTech.DBUtility.AdoHelper adoHelper = StarTech.DBUtility.AdoHelper.CreateHelper("News_Instance");
            System.Data.DataTable resourceDs = adoHelper.ExecuteSqlDataset("Select * From t_news_resource Where Recordid='" + Request.QueryString["Recordid"].ToString() + "'").Tables[0];
            if (resourceDs.Rows.Count > 0)
            {
                string filepath = this.MapPath(resourceDs.Rows[0]["path"].ToString());
                byte[] ByteFile = GetFileByte(filepath);
                if (ByteFile != null)
                {
                    string FileType = System.IO.Path.GetExtension(filepath);
                    string FileName = System.IO.Path.GetFileName(filepath);
                    Response.Clear();
                    Response.HeaderEncoding = System.Text.Encoding.Default;
                    Response.AddHeader("Content-Disposition", "attachment; filename=" + FileName);
                    Response.AddHeader("Content-Length", ByteFile.Length.ToString());
                    Response.ContentType = CheckType(FileType);
                    Response.BinaryWrite(ByteFile);
                    Response.End();
                }
                else
                {
                    Response.Write("<font color=red>找不到相关附件！【<a href='javascript:window.opener = null;window.close()'>关闭</a>】</font>");
                }
            }
        }
        else
        {
            Response.Write("<font color=red>参数错误或者权限不够  【<a href='javascript:window.close()'>关闭</a>】</font>");
        }
    }
    //获取文件二进制流
    private Byte[] GetFileByte(string path)
    {
        try
        {
            System.IO.FileStream file = new System.IO.FileStream(path, System.IO.FileMode.Open, System.IO.FileAccess.Read);
            Byte[] imgByte = new Byte[file.Length];
            file.Read(imgByte, 0, imgByte.Length);
            file.Close();
            return imgByte;
        }
        catch (Exception ex)
        {
            string str = ex.Message;
            return null;
        }
    }
    /// <summary>
    /// 根据文件的扩展名来获取对应的"输出流的HTTP MIME"类型
    /// </summary>
    /// <param name="FileType"></param>
    /// <returns></returns>
    private string CheckType(string FileType)
    {
        string ContentType;
        switch (FileType.ToLower())
        {
            case ".asf ":
                ContentType = "video/x-ms-asf ";
                break;
            case ".avi ":
                ContentType = "video/avi ";
                break;
            case ".doc ":
                ContentType = "application/msword "; break;
            case ".zip ":
                ContentType = "application/zip "; break;
            case ".xls ":
                ContentType = "application/vnd.ms-excel "; break;
            case ".gif ":
                ContentType = "image/gif "; break;
            case ".jpg ":
                ContentType = "image/jpeg "; break;
            case "jpeg ":
                ContentType = "image/jpeg "; break;
            case ".wav ":
                ContentType = "audio/wav "; break;
            case ".mp3 ":
                ContentType = "audio/mpeg3 "; break;
            case ".mpg ":
                ContentType = "video/mpeg "; break;
            case ".mepg ":
                ContentType = "video/mpeg "; break;
            case ".rtf ":
                ContentType = "application/rtf "; break;
            case ".html ":
                ContentType = "text/html "; break;
            case ".htm ":
                ContentType = "text/html "; break;
            case ".txt ":
                ContentType = "text/plain "; break;
            default:
                ContentType = "application/octet-stream ";
                break;
        }
        return ContentType;
    }