增强DropDownList和ListBox控件:保持客户端脚本添加的options
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导读:
DropDownList、ListBox由于Items是保存在ViewState中,回传后服务端会从ViewState恢复所有Items,所以,客户端对options的设置在回传后无法获取、保持。
一个解决思路是通过在页面Submit的时候,在客户端解码viewstate,找出相应items集合,根据客户端对该集合的处理,进行重新设置,然后再把更改过的viewstate重新编码提交。由于一个页面的viewstate可以是非常之大,所以这个操作在客户端的压力可能会较大。
另一个思路是将客户端对options的变更保存到隐藏域中提交,然后服务端根据该隐藏域的信息重建ListControl的items。相对而言,该实现效率更高。这个解决方案就是基于该思路来做的。我继承DropDownList、ListBox,让每个控件实例与一个隐藏域一起输出到客户端,在客户端Form.onsubmit事件时,通过脚本把客户对该Select控件所包含options的变更,以xml保存到隐藏域。然后在控件的处理CreateChildControls事件时,分析该隐藏域的内容,解析并创建出各ListItem。
以下是解决方案结构图:
在ClientOptionsHolder项目里,ClientOptionsHolder.js包含把options存入隐藏域的客户端脚本。代码如下:
function GetAttributes_BB49C217_C465_4163_97D6_69568B71A502(oElem)
{
var oAttribs = oElem.attributes;
var s = ""
for (var i = 0 i < oAttribs.length; i++) <br >
{
var oAttrib = oAttribs[i];
if(oAttrib.specified && oAttrib.nodeName!='selected')
s += ' ' + oAttrib.nodeName + '="' + oAttrib.nodeValue + '"';
}
if(oAttribs.getNamedItem("selected").value == 'true')
s += ' selected="true"';
return s;
}
function StoreClientOptions_BB49C217_C465_4163_97D6_69568B71A502(oSelect,oHidden)
{
oHidden.value = ""
for(i=0i
{
oOption = oSelect.options[i];
attrs = GetAttributes_BB49C217_C465_4163_97D6_69568B71A502(oOption);
oHidden.value +='
}
oHidden.value += "items>"
oHidden.value=escape(oHidden.value);
}
第一个函数是用来获取各个option的属性集合。只有明确设定了的属性(通过Attribute.specified判断)以及opton的select属性是true时,才添加到集合中。
第二个函数的作用是把指定Select的options以被escape编码的xml的格式放入对应隐藏域。
继承的DropDownList代码如下,非常简单:
using System;
using System.Collections.Generic;
using System.Text;
using System.Web.UI.WebControls;
namespace ZiffWong.Exercise.ControlLibrary
{
public class DropDownList : System.Web.UI.WebControls.DropDownList
{
ClientOptionsHolder _StateHolder;
public DropDownList()
: base()
{
_StateHolder = new ClientOptionsHolder(this);
}
protected override void CreateChildControls()
{
if (!Page.IsPostBack || !this.EnableViewState)
base.CreateChildControls();
else
_StateHolder.SetItemsForPostBack();
}
}
}
它在初始化的时候指定了一个ClientOptionsHolder,将自身作为参数传递给它;然后在CreateChildControls时,判断到当前页面状态如果是从客户端回传时,则让ClientOptionsHolder的SetItemsForPostBack()来处理Items的生成。可见,控件能够保存客户端设置的细节,是由ClientOptionsHolder来实现的。下面来看这个ClientOptionsHolder的具体实现:
ClientOptionsHolder.cs 1
using System; 2
using System.Collections.Generic; 3
using System.Text; 4
using System.Web.UI.WebControls; 5
using System.Web; 6
using System.Web.UI; 7
using System.Xml; 8
9
namespace ZiffWong.Exercise.ControlLibrary10
{11
/**////
12
/// Hodes options from client.13
///
14
public class ClientOptionsHolder15
{16
const string GUID = "BB49C217_C465_4163_97D6_69568B71A502"
17
string SETHIDDENFILED_FUNCTONNAME = "StoreClientOptions_" + GUID;18
Type myType = typeof(ClientOptionsHolder);19
ListControl controlToHold;20
21
string HIDDEN_FIELD_KEY22
{23
get
24
{25
return controlToHold.ClientID + "_MemField"
26
}
27
}
28
29
public ClientOptionsHolder(ListControl control)30
{31
this.controlToHold = control;32
controlToHold.PreRender += new EventHandler(control_PreRender);33
}
34
35
public void SetItemsForPostBack()36
{37
if (!controlToHold.Page.IsPostBack)38
return
39
40
XmlDocument doc = new XmlDocument();41
doc.LoadXml(HttpContext.Current.Server.UrlDecode(HttpContext.Current.Request.Form[HIDDEN_FIELD_KEY]));42
XmlNodeList nodes = doc.SelectNodes("/items/item");43
44
controlToHold.Items.Clear();45
foreach (XmlNode node in nodes)46
{47
// Set text and value.
48
string itemValue;49
string itemText;50
itemText = node.Attributes["text"] == null ? null : node.Attributes["text"].InnerText;51
itemValue = node.Attributes["value"] == null ? null : node.Attributes["value"].InnerText;52
ListItem li = new ListItem(itemText, itemValue);53
54
//Set selected.
55
if (node.Attributes["selected"] != null && node.Attributes["selected"].Value == "true")56
li.Selected = true
57
58
/**/////Those ListItems with "Enabled"==false will not be added to items collection because they will not render any outputs.
59
//if (node.Attributes["disabled"] != null)60
//li.Enabled = false;61
62
//Apply other attributes such as "label","isMultiLine" etc.
63
foreach (XmlAttribute attr in node.Attributes)64
{65
string attrName = attr.Name;66
if (attrName != "text" && attrName != "value" && attrName != "selected")67
{68
li.Attributes.Add(attrName, attr.Value);69
}
70
}
71
72
controlToHold.Items.Add(li);73
}
74
}
75
76
void control_PreRender(object sender, EventArgs e)77
{78
string senderClientID = ((ListControl)sender).ClientID;79
Control control = (Control)sender;80
string onSubmitScriptKey = string.Format("SetHiddenField_{0}", senderClientID);81
if (!control.Page.ClientScript.IsOnSubmitStatementRegistered(myType, onSubmitScriptKey))82
{83
control.Page.ClientScript.RegisterClientScriptResource(myType, "ZiffWong.Exercise.ControlLibrary.ClientOptionsHolders.js");84
85
string scriptBody = SETHIDDENFILED_FUNCTONNAME + string.Format("(document.all.{0},document.all.{1});", senderClientID, HIDDEN_FIELD_KEY);86
control.Page.ClientScript.RegisterOnSubmitStatement(myType, onSubmitScriptKey, scriptBody);87
control.Page.ClientScript.RegisterClientScriptBlock(myType, HIDDEN_FIELD_KEY, string.Format(""hidden/" id=/"
{0}/" name=/"
{0}/"/>", HIDDEN_FIELD_KEY));88
89
}
90
}
91
}
92
}
93
它的初始化函数中把传入的ListControl的PreRender事件挂接control_PreRender 函数,该函数首先把上面的Javascript资源链接注册到页面,然后在客户端的OnSubmit中添加对保存options到隐藏域的JS函数的调用。最后,把隐藏域输出到客户端。
SetItemsForPostBack()由挂接该ClientOptionsHolder的ListControl在CreateChildControls时调用。它解析客户端隐藏域里面的xml,据此生成所有Items集合。
为了能够使用dll内嵌的资源文件,需要在AssemblyInfo.cs中做如下设置:
[assembly: System.Web.UI.TagPrefix("ZiffWong.Exercise.ControlLibrary", "mstc")]
[assembly: System.Web.UI.WebResource("ZiffWong.Exercise.ControlLibrary.ClientOptionsHolders.js", "application/x-javascript")]
注意在资源文件ClientOptionsHolders.js前需要加上该控件所在程序集的默认命名空间。程序中对该资源的引用也需要如此处理。
对ListBox的处理和DropDownList一样:
ListBox.csCode highlighting produced by Actipro CodeHighlighter (freeware)
http://www.CodeHighlighter.com/
-->
using System;
using System.Collections.Generic;
using System.Text;
using System.Web.UI.WebControls;
namespace ZiffWong.Exercise.ControlLibrary
{
public class ListBox : System.Web.UI.WebControls.ListBox
{
ClientOptionsHolder _StateHolder;
public ListBox()
: base()
{
_StateHolder = new ClientOptionsHolder(this);
}
protected override void CreateChildControls()
{
if (!Page.IsPostBack || !this.EnableViewState)
base.CreateChildControls();
else
_StateHolder.SetItemsForPostBack();
}
}
}
本文转自
http://www.cnblogs.com/meil/archive/2006/10/19/533838.html
DropDownList、ListBox由于Items是保存在ViewState中,回传后服务端会从ViewState恢复所有Items,所以,客户端对options的设置在回传后无法获取、保持。
一个解决思路是通过在页面Submit的时候,在客户端解码viewstate,找出相应items集合,根据客户端对该集合的处理,进行重新设置,然后再把更改过的viewstate重新编码提交。由于一个页面的viewstate可以是非常之大,所以这个操作在客户端的压力可能会较大。
另一个思路是将客户端对options的变更保存到隐藏域中提交,然后服务端根据该隐藏域的信息重建ListControl的items。相对而言,该实现效率更高。这个解决方案就是基于该思路来做的。我继承DropDownList、ListBox,让每个控件实例与一个隐藏域一起输出到客户端,在客户端Form.onsubmit事件时,通过脚本把客户对该Select控件所包含options的变更,以xml保存到隐藏域。然后在控件的处理CreateChildControls事件时,分析该隐藏域的内容,解析并创建出各ListItem。
以下是解决方案结构图:
在ClientOptionsHolder项目里,ClientOptionsHolder.js包含把options存入隐藏域的客户端脚本。代码如下:
function GetAttributes_BB49C217_C465_4163_97D6_69568B71A502(oElem)
{
var oAttribs = oElem.attributes;
var s = ""
for (var i = 0 i < oAttribs.length; i++) <br >
{
var oAttrib = oAttribs[i];
if(oAttrib.specified && oAttrib.nodeName!='selected')
s += ' ' + oAttrib.nodeName + '="' + oAttrib.nodeValue + '"';
}
if(oAttribs.getNamedItem("selected").value == 'true')
s += ' selected="true"';
return s;
}
function StoreClientOptions_BB49C217_C465_4163_97D6_69568B71A502(oSelect,oHidden)
{
oHidden.value = ""
for(i=0i
{
oOption = oSelect.options[i];
attrs = GetAttributes_BB49C217_C465_4163_97D6_69568B71A502(oOption);
oHidden.value +='
}
oHidden.value += "items>"
oHidden.value=escape(oHidden.value);
}
第一个函数是用来获取各个option的属性集合。只有明确设定了的属性(通过Attribute.specified判断)以及opton的select属性是true时,才添加到集合中。
第二个函数的作用是把指定Select的options以被escape编码的xml的格式放入对应隐藏域。
继承的DropDownList代码如下,非常简单:
using System;
using System.Collections.Generic;
using System.Text;
using System.Web.UI.WebControls;
namespace ZiffWong.Exercise.ControlLibrary
{
public class DropDownList : System.Web.UI.WebControls.DropDownList
{
ClientOptionsHolder _StateHolder;
public DropDownList()
: base()
{
_StateHolder = new ClientOptionsHolder(this);
}
protected override void CreateChildControls()
{
if (!Page.IsPostBack || !this.EnableViewState)
base.CreateChildControls();
else
_StateHolder.SetItemsForPostBack();
}
}
}
它在初始化的时候指定了一个ClientOptionsHolder,将自身作为参数传递给它;然后在CreateChildControls时,判断到当前页面状态如果是从客户端回传时,则让ClientOptionsHolder的SetItemsForPostBack()来处理Items的生成。可见,控件能够保存客户端设置的细节,是由ClientOptionsHolder来实现的。下面来看这个ClientOptionsHolder的具体实现:
ClientOptionsHolder.cs 1
using System; 2
using System.Collections.Generic; 3
using System.Text; 4
using System.Web.UI.WebControls; 5
using System.Web; 6
using System.Web.UI; 7
using System.Xml; 8
9
namespace ZiffWong.Exercise.ControlLibrary10
{11
/**////
12
/// Hodes options from client.13
///
14
public class ClientOptionsHolder15
{16
const string GUID = "BB49C217_C465_4163_97D6_69568B71A502"
17
string SETHIDDENFILED_FUNCTONNAME = "StoreClientOptions_" + GUID;18
Type myType = typeof(ClientOptionsHolder);19
ListControl controlToHold;20
21
string HIDDEN_FIELD_KEY22
{23
get
24
{25
return controlToHold.ClientID + "_MemField"
26
}
27
}
28
29
public ClientOptionsHolder(ListControl control)30
{31
this.controlToHold = control;32
controlToHold.PreRender += new EventHandler(control_PreRender);33
}
34
35
public void SetItemsForPostBack()36
{37
if (!controlToHold.Page.IsPostBack)38
return
39
40
XmlDocument doc = new XmlDocument();41
doc.LoadXml(HttpContext.Current.Server.UrlDecode(HttpContext.Current.Request.Form[HIDDEN_FIELD_KEY]));42
XmlNodeList nodes = doc.SelectNodes("/items/item");43
44
controlToHold.Items.Clear();45
foreach (XmlNode node in nodes)46
{47
// Set text and value.
48
string itemValue;49
string itemText;50
itemText = node.Attributes["text"] == null ? null : node.Attributes["text"].InnerText;51
itemValue = node.Attributes["value"] == null ? null : node.Attributes["value"].InnerText;52
ListItem li = new ListItem(itemText, itemValue);53
54
//Set selected.
55
if (node.Attributes["selected"] != null && node.Attributes["selected"].Value == "true")56
li.Selected = true
57
58
/**/////Those ListItems with "Enabled"==false will not be added to items collection because they will not render any outputs.
59
//if (node.Attributes["disabled"] != null)60
//li.Enabled = false;61
62
//Apply other attributes such as "label","isMultiLine" etc.
63
foreach (XmlAttribute attr in node.Attributes)64
{65
string attrName = attr.Name;66
if (attrName != "text" && attrName != "value" && attrName != "selected")67
{68
li.Attributes.Add(attrName, attr.Value);69
}
70
}
71
72
controlToHold.Items.Add(li);73
}
74
}
75
76
void control_PreRender(object sender, EventArgs e)77
{78
string senderClientID = ((ListControl)sender).ClientID;79
Control control = (Control)sender;80
string onSubmitScriptKey = string.Format("SetHiddenField_{0}", senderClientID);81
if (!control.Page.ClientScript.IsOnSubmitStatementRegistered(myType, onSubmitScriptKey))82
{83
control.Page.ClientScript.RegisterClientScriptResource(myType, "ZiffWong.Exercise.ControlLibrary.ClientOptionsHolders.js");84
85
string scriptBody = SETHIDDENFILED_FUNCTONNAME + string.Format("(document.all.{0},document.all.{1});", senderClientID, HIDDEN_FIELD_KEY);86
control.Page.ClientScript.RegisterOnSubmitStatement(myType, onSubmitScriptKey, scriptBody);87
control.Page.ClientScript.RegisterClientScriptBlock(myType, HIDDEN_FIELD_KEY, string.Format(""hidden/" id=/"
{0}/" name=/"
{0}/"/>", HIDDEN_FIELD_KEY));88
89
}
90
}
91
}
92
}
93
它的初始化函数中把传入的ListControl的PreRender事件挂接control_PreRender 函数,该函数首先把上面的Javascript资源链接注册到页面,然后在客户端的OnSubmit中添加对保存options到隐藏域的JS函数的调用。最后,把隐藏域输出到客户端。
SetItemsForPostBack()由挂接该ClientOptionsHolder的ListControl在CreateChildControls时调用。它解析客户端隐藏域里面的xml,据此生成所有Items集合。
为了能够使用dll内嵌的资源文件,需要在AssemblyInfo.cs中做如下设置:
[assembly: System.Web.UI.TagPrefix("ZiffWong.Exercise.ControlLibrary", "mstc")]
[assembly: System.Web.UI.WebResource("ZiffWong.Exercise.ControlLibrary.ClientOptionsHolders.js", "application/x-javascript")]
注意在资源文件ClientOptionsHolders.js前需要加上该控件所在程序集的默认命名空间。程序中对该资源的引用也需要如此处理。
对ListBox的处理和DropDownList一样:
ListBox.csCode highlighting produced by Actipro CodeHighlighter (freeware)
http://www.CodeHighlighter.com/
-->
using System;
using System.Collections.Generic;
using System.Text;
using System.Web.UI.WebControls;
namespace ZiffWong.Exercise.ControlLibrary
{
public class ListBox : System.Web.UI.WebControls.ListBox
{
ClientOptionsHolder _StateHolder;
public ListBox()
: base()
{
_StateHolder = new ClientOptionsHolder(this);
}
protected override void CreateChildControls()
{
if (!Page.IsPostBack || !this.EnableViewState)
base.CreateChildControls();
else
_StateHolder.SetItemsForPostBack();
}
}
}
本文转自
http://www.cnblogs.com/meil/archive/2006/10/19/533838.html
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