三层架构上传图片只能到本机工程文件夹下，不能传到服务器上

如题，我的代码如下
  protected void UploadBtn_Click(object sender, EventArgs e)
        {
           
            if (this.UploadFile.PostedFile.ContentLength != 0)
            {
                if (this.UploadFile.Value != "")
                {
                    string mFullName = this.UploadFile.PostedFile.FileName;//获取图片的完整路径和文件名
                    string mFileName = mFullName.Substring(mFullName.LastIndexOf("\\") + 1);//获取图片的文件名
                    string mFileType = mFileName.Substring(mFileName.LastIndexOf(".") + 1);//获取图片的后缀
                    if (mFileType == "jpg" || mFileType == "bmp" || mFileType == "gif")
                    {
                       // this.UploadFile.PostedFile.SaveAs(Server.MapPath("~") + "NewsPublishStyle/images" + mFileName);
                        //this.UploadFile.PostedFile.SaveAs(Server.MapPath("NewsPublishStyle/images") + mFileName);
                        this.PreViewImage.ImageUrl = "NewsPublishStyle/images/" + mFileName;
                        this.PathLabel.Text = "NewsPublishStyle/images/" + mFileName;
                    }
                    else
                    {
                        Response.Write("<script>alert('上传图片格式不正确！')<script/>");
                    }
                }
                else
                { }
            }
        }