文件下载功能

代码如下：

/// <summary>
/// 附件下载
/// </summary>
/// <param name="attachId">附件ID</param>
public void DownloadAttach(int attachId)
{
    Edu_Attach edu_Attach = edu_AttachService.findById<Edu_Attach>(attachId);
    if (edu_Attach != null)
    {
        HttpContext context = (HttpContext)ctx.web.Context;
        if (context != null)
        {
            string filePathName = PathHelper.Map(sys.Path.DiskPhoto) + edu_Attach.AttachContent.Replace("/static/upload/image", "").Replace("/", "\");
            int pos = filePathName.LastIndexOf("\");
            string fileName = filePathName.Substring(pos + 1);
            string UserAgent = context.Request.ServerVariables["http_user_agent"].ToLower();
            if (UserAgent.IndexOf("firefox") == -1)
            {
                //非火狐浏览器
                context.Response.AddHeader("content-disposition", "attachment;filename=" + HttpUtility.UrlEncode(edu_Attach.AttachName));
            }
            else
            {
                context.Response.AddHeader("content-disposition", "attachment;filename=" + edu_Attach.AttachName);
            }
            FileStream fs = new FileStream(filePathName, FileMode.Open, FileAccess.Read);
            byte[] bArr = new byte[fs.Length];
            fs.Read(bArr, 0, bArr.Length);
            fs.Close();
            context.Response.ContentEncoding = Encoding.UTF8;
            context.Response.BinaryWrite(bArr);
            context.Response.Flush();
            context.Response.End();
        }
    }
}