ASP.NET2.0状态管理系列(5) 控件状态 Control state

A page developer can disable view state for the page or for an individual control for performance. However, control state cannot be disabled.

 

下面的例子解释控件状态和视图状态

 

1.创建自定义ASP.NET服务器控件

 

自定义控件代码
  1 // IndexButton.cs
  2 using System;
  3 using System.ComponentModel;
  4 using System.Security.Permissions;
  5 using System.Web;
  6 using System.Web.UI;
  7 using System.Web.UI.WebControls;
  8 
  9 namespace Samples.AspNet.CS.Controls
 10 {
 11     [
 12     AspNetHostingPermission(SecurityAction.Demand,
 13         Level = AspNetHostingPermissionLevel.Minimal),
 14     AspNetHostingPermission(SecurityAction.InheritanceDemand,
 15         Level = AspNetHostingPermissionLevel.Minimal),
 16     ToolboxData("<{0}:IndexButton runat=\"server\"> </{0}:IndexButton>")
 17     ]
 18     public class IndexButton : Button
 19     {
 20         private int indexValue;
 21 
 22         [
 23         Bindable(true),
 24         Category("Behavior"),
 25         DefaultValue(0),
 26         Description("The index stored in control state.")
 27         ]
 28         public int Index
 29         {
 30             get
 31             {
 32                 return indexValue;
 33             }
 34             set
 35             {
 36                 indexValue = value;
 37             }
 38         }
 39 
 40         [
 41         Bindable(true),
 42         Category("Behavior"),
 43         DefaultValue(0),
 44         Description("The index stored in view state.")
 45         ]
 46         public int IndexInViewState
 47         {
 48             get
 49             {
 50                 object obj = ViewState["IndexInViewState"];
 51                 return (obj == null) ? 0 : (int)obj;
 52             }
 53             set
 54             {
 55                 ViewState["IndexInViewState"] = value;
 56             }
 57         }
 58 
 59         protected override void OnInit(EventArgs e)
 60         {
 61             base.OnInit(e);
 62             Page.RegisterRequiresControlState(this);
 63         }
 64 
 65         protected override object SaveControlState()
 66         {
 67             // Invoke the base class's method and
 68             // get the contribution to control state
 69             // from the base class.
 70             // If the indexValue field is not zero
 71             // and the base class's control state is not null,
 72             // use Pair as a convenient data structure
 73             // to efficiently save 
 74             // (and restore in LoadControlState)
 75             // the two-part control state
 76             // and restore it in LoadControlState.
 77 
 78             object obj = base.SaveControlState();
 79 
 80             if (indexValue != 0)
 81             {
 82                 if (obj != null)
 83                 {
 84                     return new Pair(obj, indexValue);
 85                 }
 86                 else
 87                 {
 88                     return (indexValue);
 89                 }
 90             }
 91             else
 92             {
 93                 return obj;
 94             }
 95         }
 96 
 97         protected override void LoadControlState(object state)
 98         {
 99             if (state != null)
             {
                 Pair p = state as Pair;
                 if (p != null)
                 {
                     base.LoadControlState(p.First);
                     indexValue = (int)p.Second;
                 }
                 else
                 {
                     if (state is int)
                     {
                         indexValue = (int)state;
                     }
                     else
                     {
                         base.LoadControlState(state);
                     }
                 }
             }
         }
 
     }
 }

 

2.编译控件为程序集

 

csc /t:library /out:Samples.AspNet.CS.Controls.dll D:\indexbutton.cs

 

3.测试自定义控件控件状态

 

在Web.config文件中注册自定义控件，每个页面都可以使用。

 

 <pages>
       <controls>
         <add tagPrefix="aspSample" 
           namespace="Samples.AspNet.CS.Controls" 
           assembly="Samples.AspNet.CS.Controls" >
         </add>
       </controls>
     </pages>

 

4.实现控件状态的条件

控件必须重写 OnInit，SaveControlState，LoadControlState方法。