C#中的文件上传

 protected void Button1_Click(object sender, EventArgs e)
    {

        try
        {
            if (this.FileUpload1.PostedFile.FileName == null)
            {
                Response.Write("<script language=javascript>alert('请选择你要上传的文件！');</script>");
            }
            else
            {
                string filePath = FileUpload1.PostedFile.FileName;
                string fileName = filePath.Substring(filePath.LastIndexOf("\\") + 1);
                string fileType = (filePath.Substring(filePath.LastIndexOf(".") + 1)).ToLower();
                string serverPath = Server.MapPath("~/upload/")+ fileName;               
                if (fileType == "bmp" || fileType == "gif" || fileType == "jpg" || fileType == "doc" || fileType == "xls" || fileType == "rar")
                {
                    FileUpload1.PostedFile.SaveAs(serverPath);
                    this.TextBox1.Text = "/upload/" + fileName;
                    Response.Write("<script language=javascript>alert('当前文件上传成功！');</script>");
                }
                else
                {
                    Response.Write("<script language=javascript>alert('文件上传失败！只能上传以下文件格式的文件：bmp,gif,jpg,doc,xls,rar。');</script>");
                }
            }
        }
        catch (Exception ex)
        {
            Response.Write(ex.Message);
        }

    }