描述：在button事件中注册一个上传事件

代码详解：

 protected void FileUpload_Click(object sender, EventArgs e)

        {

            bool fileIsvaild = false;    //初始化一个bool型为false的fileIsvaild

            if (this.FileUpload1.HasFile)//哈希判读文件是否存在

            {

               

                string fileExtension = System.IO.Path.GetExtension(this.FileUpload1.FileName).ToLower();//获取文件名并转化为小写

                string[] restrictExtension = { ".gif", ".jpg", "png", ".doc", ".txt" };//设置文件匹配格式

                for (int i = 0; i < restrictExtension.Length; i++)

                {

                    if (fileExtension == restrictExtension[i])

                    {

                        fileIsvaild = true;

                    }

                }

                if (fileIsvaild == true)

                {

                    try

                    {

                        this.Image1.ImageUrl = "~/myfile/" + FileUpload1.FileName;  //获取上传文件名

                        this.FileUpload1.SaveAs(Server.MapPath("~/myfile/") + FileUpload1.FileName);//保存文件

                        this.Label5.Text = "上传成功";

                        this.Label5.Text += "<br/>";

                        this.Label5.Text += FileUpload1.FileName + "<br/>";

                        this.Label5.Text += FileUpload1.FileBytes + "<br/>";

                        this.Label5.Text += FileUpload1.ControlStyle + "<br/>";

                    }

                    catch (Exception ex)

                    {

                        this.Label5.Text = "无法上传" + ex.Message;

                    }

                }

            }

            else

            {

                Response.Write("<script>alert('上传的文件不存在！')</script>");

            }

        }