asp.net2.0服务器控件(图片上传的服务器控件)

一直都觉得图片上传是个比较麻烦的事,虽然在asp.net2.0中FileUpload控件已经把它变得十分简单,但还是有不太好用的地方,学了几天的服务器控件,最后试着做了一个图片上传用的控件,这个只是满足最基本的需要,还有许多不足的地方需要改进,由于第一次写服务器控件,还有许多地方也不知道是否合理,希望大家指出.

主要完成的功能是:使图片上传控件可以像textbox控件那样在detailsview控件中使用,

以下为代码:

 

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel.Design;

namespace WebControlLibrary
{
    [DefaultProperty("Text")]
    [ToolboxData("<{0}:UploadImg runat=server></{0}:UploadImg>")]
    public class UploadImg :CompositeControl
    {
        private Button _button;
        private Image _image;
        private FileUpload _fileUpload;
        private Label LabMessage1;
        private string _uploadImgImageUrl="~/img/net/not.gif";
        private static readonly object EventSubmitKey = new object();
       

        [Bindable(true)]
        [Category("Appearance")]
        [DefaultValue("")]
        [Localizable(true)]
        public string UploadImgImageUrl
        {
            get
            {
                EnsureChildControls();
                String s = (String)ViewState["UploadImgImageUrl"];
                return ((s == null) ? _uploadImgImageUrl : s);
            }

            set
            {
                EnsureChildControls();
                ViewState["UploadImgImageUrl"] = value;
               _image.ImageUrl= value;
            }
        }

 

 

        public event EventHandler Submit
        {
            add
            {
                Events.AddHandler(EventSubmitKey, value);
            }
            remove
            {
                Events.RemoveHandler(EventSubmitKey,value);
            }
        }

        protected virtual void OnSubmit(EventArgs e)
        {
            　EventHandler SubmitHandler = (EventHandler) Events[EventSubmitKey];
　　　if (SubmitHandler != null) {
　　　　SubmitHandler(this, e);
　　　}

        }
        // 实现Submit事件引发的事件处理程序
　　private void _button_Click(Object source, EventArgs e)
  {
　　　OnSubmit(EventArgs.Empty);
      bool fileOK = false;

   string path =Page.Server.MapPath("~/img/guest/");

   if (_fileUpload.HasFile)
   {
       String fileExtension = System.IO.Path.GetExtension(_fileUpload.FileName).ToLower();
       String[] allowedExtensions = { ".gif", ".png", ".bmp", ".jpg" };
       for (int i = 0; i < allowedExtensions.Length; i++)
       {
           if (fileExtension == allowedExtensions[i])
           {
               fileOK = true;
           }
       }
   }
   if (fileOK)
   {

       try
       {
           DateTime dt = DateTime.Now;
           string theFileName = dt.Second + dt.Month + dt.Day + dt.DayOfYear + _fileUpload.FileName;
           _fileUpload.SaveAs(path + theFileName);

         

         

           UploadImgImageUrl = "~/img/guest/" + theFileName;

           LabMessage1.Text = "文件上传成功.";

       }
       catch (Exception ex)
       {
           LabMessage1.Text = "文件上传不成功.";
       }
   }
   else
   {
       LabMessage1.Text = "只能够上传图片文件.";
   }
　　}
　　// 重写ICompositeControlDesignerAccessor接口的RecreateChildContrls方法
　　protected override void RecreateChildControls() {
　　　EnsureChildControls();
　　}

　　//重写CreateChildControls方法，将子控件添加到复合控件中

        protected override void CreateChildControls()
        {
            Controls.Clear();
            _button = new Button();
            _image = new Image();
            _fileUpload = new FileUpload();
            LabMessage1 = new Label();
            _button.ID = "UploadImgbtn";
            _button.Text = "上传";
            _button.Click += new EventHandler(_button_Click);
            _image.Width = 100;
            _image.Height = 80;
            _image.ImageUrl = UploadImgImageUrl;
            this.Controls.Add(_button);
            this.Controls.Add(_image);
            this.Controls.Add(_fileUpload);
            this.Controls.Add(LabMessage1);
        }

       
　　//重写Render方法，呈现控件中其他的HTML代码

　　protected override void Render(HtmlTextWriter output) {
　　　output.AddAttribute(HtmlTextWriterAttribute.Border, "0px");
　　　output.AddAttribute(HtmlTextWriterAttribute.Cellpadding, "5px"); 　
　　　output.AddAttribute(HtmlTextWriterAttribute.Cellspacing, "0px"); 　
　　　output.RenderBeginTag(HtmlTextWriterTag.Table);
　　　output.RenderBeginTag(HtmlTextWriterTag.Tr); 　　
　　　output.RenderBeginTag(HtmlTextWriterTag.Td);
　　  _image.RenderControl(output);
　　　output.RenderEndTag();
　　　output.RenderBeginTag(HtmlTextWriterTag.Td);
      _fileUpload.RenderControl(output);
　　　_button.RenderControl(output);
　　　output.RenderEndTag();
　　　output.RenderEndTag();
      output.RenderBeginTag(HtmlTextWriterTag.Tr);
      output.RenderBeginTag(HtmlTextWriterTag.Td);
      LabMessage1.RenderControl(output);
      output.RenderEndTag();
      output.RenderEndTag();
　　　output.RenderEndTag();
　　}

    }
}