扩展DropDownList控件和ListBox控件(1) - 支持分组功能(optgroup标签)

using System; 
using System.Collections.Generic; 
using System.Text; 
 
using System.Web.UI.WebControls; 
using System.Web.UI; 
 
[assembly: System.Web.UI.WebResource( "YYControls.SmartDropDownList.Resources.Icon.bmp",  "image/bmp")] 
 
namespace YYControls 
{ 
         /// <summary> 
         /// SmartDropDownList类，继承自DropDownList 
         /// </summary> 
        [ToolboxData( @"<{0}:SmartDropDownList runat='server'></{0}:SmartDropDownList>")] 
        [System.Drawing.ToolboxBitmap( typeof(YYControls.Resources.Icon),  "SmartDropDownList.bmp")] 
         public partial  class SmartDropDownList : DropDownList 
        { 
                 /// <summary> 
                 /// 构造函数 
                 /// </summary> 
                 public SmartDropDownList() 
                { 
 
                } 
 
                 /// <summary> 
                 /// 将控件的内容呈现到指定的编写器中 
                 /// </summary> 
                 /// <param name="writer">writer</param> 
                 protected  override  void RenderContents(HtmlTextWriter writer)    
                { 
                         // 呈现Option或OptionGroup 
                        OptionGroupRenderContents(writer); 
                } 
        } 
}

using System; 
using System.Collections.Generic; 
using System.Text; 
 
using System.ComponentModel; 
using System.Web.UI; 
 
namespace YYControls 
{ 
         /// <summary> 
         /// SmartDropDownList类的属性部分 
         /// </summary> 
         public partial  class SmartDropDownList 
        { 
                 /// <summary> 
                 /// 用于添加SmartDropDownList的分组项的ListItem的Value值 
                 /// </summary> 
                [ 
                Browsable( true), 
                Description( "用于添加DropDownList的分组项的ListItem的Value值"), 
                Category( "扩展") 
                ] 
                 public  virtual  string OptionGroupValue 
                { 
                        get 
                        { 
                                 string s = ( string)ViewState[ "OptionGroupValue"]; 
 
                                 return (s ==  null) ?  "optgroup" : s; 
                        } 
                        set 
                        { 
                                ViewState[ "OptionGroupValue"] = value; 
                        } 
                } 
        } 
}

using System; 
using System.Collections.Generic; 
using System.Text; 
 
using System.Data; 
using System.Web.UI.WebControls; 
using System.Web.UI; 
using System.Web; 
 
namespace YYControls 
{ 
         /// <summary> 
         /// SmartDropDownList类的属性部分 
         /// </summary> 
         public partial  class SmartDropDownList 
        { 
                 /// <summary> 
                 /// 呈现Option或OptionGroup 
                 /// </summary> 
                 /// <param name="writer">writer</param> 
                 private  void OptionGroupRenderContents(HtmlTextWriter writer) 
                { 
                         // 是否需要呈现OptionGroup的EndTag 
                         bool writerEndTag =  false; 
 
                         foreach (ListItem li  in  this.Items) 
                        { 
                                 // 如果没有optgroup属性则呈现Option 
                                 if (li.Value !=  this.OptionGroupValue) 
                                { 
                                         // 呈现Option 
                                        RenderListItem(li, writer); 
                                } 
                                 // 如果有optgroup属性则呈现OptionGroup 
                                 else 
                                { 
                                         if (writerEndTag) 
                                                 // 呈现OptionGroup的EndTag 
                                                OptionGroupEndTag(writer); 
                                         else 
                                                writerEndTag =  true; 
 
                                         // 呈现OptionGroup的BeginTag 
                                        OptionGroupBeginTag(li, writer); 
                                } 
                        } 
 
                         if (writerEndTag) 
                                 // 呈现OptionGroup的EndTag 
                                OptionGroupEndTag(writer); 
                } 
 
                 /// <summary> 
                 /// 呈现OptionGroup的BeginTag 
                 /// </summary> 
                 /// <param name="li">OptionGroup数据项</param> 
                 /// <param name="writer">writer</param> 
                 private  void OptionGroupBeginTag(ListItem li, HtmlTextWriter writer) 
                { 
                        writer.WriteBeginTag( "optgroup"); 
                         
                         // 写入OptionGroup的label 
                        writer.WriteAttribute( "label", li.Text); 
 
                         foreach ( string key  in li.Attributes.Keys) 
                        { 
                                 // 写入OptionGroup的其它属性 
                                writer.WriteAttribute(key, li.Attributes[key]); 
                        } 
 
                        writer.Write(HtmlTextWriter.TagRightChar); 
                        writer.WriteLine(); 
                } 
 
                 /// <summary> 
                 /// 呈现OptionGroup的EndTag 
                 /// </summary> 
                 /// <param name="writer">writer</param> 
                 private  void OptionGroupEndTag(HtmlTextWriter writer) 
                { 
                        writer.WriteEndTag( "optgroup"); 
                        writer.WriteLine(); 
                } 
 
                 /// <summary> 
                 /// 呈现Option 
                 /// </summary> 
                 /// <param name="li">Option数据项</param> 
                 /// <param name="writer">writer</param> 
                 private  void RenderListItem(ListItem li, HtmlTextWriter writer) 
                { 
                        writer.WriteBeginTag( "option"); 
 
                         // 写入Option的Value 
                        writer.WriteAttribute( "value", li.Value,  true); 
 
                         if (li.Selected) 
                        { 
                                 // 如果该Option被选中则写入selected 
                                writer.WriteAttribute( "selected",  "selected",  false); 
                        } 
 
                         foreach ( string key  in li.Attributes.Keys) 
                        { 
                                 // 写入Option的其它属性 
                                writer.WriteAttribute(key, li.Attributes[key]); 
                        } 
 
                        writer.Write(HtmlTextWriter.TagRightChar); 
 
                         // 写入Option的Text 
                        HttpUtility.HtmlEncode(li.Text, writer); 
 
                        writer.WriteEndTag( "option"); 
                        writer.WriteLine(); 
                } 
        } 
}