自定义控件学习笔记（六）

自定义控件学习笔记（六）－－生成回发

1。要点

1）生成回发的含义－－不用用户点提交按钮，就自动提交表单

2）使用Page.ClientScript.GetPostBackEventReference(post)达到回发的目的

2。控件

 

using  System;
using  System.Web.UI;
using  System.Collections.Specialized;


namespace  TestCustomControl
... {
    public class GenerateAutoPostBack : Control, IPostBackDataHandler
    ...{
        bool autoPostBack = false;

        public string Text
        ...{
            get
            ...{
                if (ViewState["myText"] != null)
                ...{
                    string text = (string)ViewState["myText"];
                    return text;
                }
                else
                ...{
                    return "";
                }

            }
            set ...{ ViewState["myText"] = value; }
        }
        
        public bool AutoPostBack
        ...{
            get...{return autoPostBack;}
            set...{autoPostBack=value;}
        }
        
        public event EventHandler TextChanged;

        protected override void Render(HtmlTextWriter writer)
        ...{
            writer.WriteBeginTag("input");
            writer.WriteAttribute("name", UniqueID);

            if (ID != null)
            ...{
                writer.WriteAttribute("id", ClientID);
            }

            if (Text.Length > 0)
            ...{
                writer.WriteAttribute("value", Text);


            }
            
            if(autoPostBack)
            ...{
                //writer.WriteAttribute("onchange","javascript:"+Page.GetPostBackEventReference(this));
                PostBackOptions post = new PostBackOptions(this);
                writer.WriteAttribute("onchange", "javascript:" + Page.ClientScript.GetPostBackEventReference(post));
            }
            
            writer.Write(HtmlTextWriter.TagRightChar);

            writer.WriteEndTag("input");


        }

        public bool LoadPostData(string postDataKey, NameValueCollection postCollection)
        ...{

            //先用户修改文字并回传后，text被修改（Render）之前引发此事件。
            //流程：render－》显示－》用户修改－》LoadPostData－》（RaisePostDataChangedEvent）－》Render（第二次）
            string temp = Text;
            Text = postCollection[postDataKey];

            if (temp != Text)
                return true;//引发RaisePostDataChangedEvent
            else
                return false;
        }

        public void RaisePostDataChangedEvent()
        ...{
            if (TextChanged != null)//指客户端使用控件时候，写入了 （OnTextChanged="MethodName"),否则则认为用户没有处理此事件
            ...{
                TextChanged(this, new EventArgs());
            }
        }
    }
}

 

3。用法

 

<% ... @ Page Language="C#" AutoEventWireup="true" CodeFile="GeneratePostBack.aspx.cs" Inherits="TestCustomControl_First_GeneratePostBack"  %>
<% ... @ Register Assembly="GenerateAutoPostBack" Namespace="TestCustomControl" TagPrefix="Surance" %>
<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >

< html  xmlns ="http://www.w3.org/1999/xhtml"   >
< head  runat ="server" >
     < title > 无标题页 </ title >
</ head >
< body >
     < form  id ="form1"  runat ="server" >
     < div >
     < Surance:GenerateAutoPostBack  ID ="G1"  Runat ="server"  AutoPostBack ="true"  OnTextChanged ="G1_OnTextChanged"   />
     </ div >
     </ form >
</ body >
</ html >

 

后台

 

  protected   void  G1_OnTextChanged( object  sender, EventArgs e)
     ... {
        Response.Write("Generate");
    }