mylabel.cs

asp.net经典案例资料

using System;
using System.Web;
using System.Web.UI;

namespace snowy
{
  public class MyLabel : Control, IPostBackEventHandler
  {
    // Define a Server-side event click
    public event EventHandler Click;

    string HiddenCountID
    {
      get{ return "__" + this.ClientID + "_Count"; }
    }
    string HiddenTextID
    {
      get{ return "__" + this.ClientID + "_Text"; }
    }

    public int Count
    {
      get
      {
        object obj = ViewState["Count"];
        return (obj == null) ? 0 : (int)obj;
      }
      set { ViewState["Count"] = value; }
    }

    public string Text
    {
      get
      {
        object obj = ViewState["Text"];
        return (obj == null) ? String.Empty : (string)obj;
      }
      set { ViewState["Text"] = value; }
    }

    protected override void OnPreRender(EventArgs e)
    {
      base.OnPreRender(e);

      if (Page != null)
      {
        Page.RegisterHiddenField(HiddenCountID, Count.ToString());
        Page.RegisterHiddenField(HiddenTextID, Text.ToString());
      }

      string script = "<script language=javascript>\n";
      script += "    function showcount()\n";
      script += "    {\n";
      script += "      document.all[\"" + this.ClientID + "\"].innerText = 'You have clicked ' + document.all[\"" + HiddenCountID + "\"].value + ' times';\n";
      script += "    }\n";
      script += "    function showtext()\n";
      script += "    {\n";
      script += "      document.all[\"" + this.ClientID + "\"].innerText = document.all[\"" + HiddenTextID + "\"].value;\n";
      script += "    }\n";
      script += "    </script>";

       if(!Page.IsClientScriptBlockRegistered("mylabelscript"))
         Page.RegisterClientScriptBlock("mylabelscript", script);
    }

    
    public void RaisePostBackEvent(string eventArgument)
    {
      Count++;
      OnClick(EventArgs.Empty);
    }

    protected void OnClick(EventArgs arg)
    {
      if(Click != null)
        Click(this, arg);
    }

    protected override void Render(HtmlTextWriter writer)
    {
      string postback = "";
      if (Page != null)
        postback = Page.GetPostBackEventReference(this) + ";";

          string id = "id=\"" + this.ClientID + "\"";
          string click = "onclick=\"" + postback + "\"";
          string mouseEnter = "onmouseenter=\"showcount();\"";
          string mouseLeave = "onmouseleave=\"showtext();\"";
          writer.Write("<span " + id + " " + click + " " + mouseEnter + " " + mouseLeave +  ">" + this.Text + "</span>");
    }
  }
}