DropDownList自定义控件，让你的分类更清晰

记得上次做论坛，一个功能就是合并2个子板块的主题，用级联的2个DropDownList也是可以完成，那样我们要合并的时候总共就有4个DropDownList控件，觉得界面友好；看到Discuz是2个下拉列表进行合并的，网上找了一些资料，然后写了这个小源码，在这里和大家分享一下！

运行效果图，如下所示（深黑的地方选不中，因为那是上一级的分类）：

项目结构图如下所示：

Controls类库SmartDropDownList.cs代码如下所示：

SmartDropDownList.cs

 1 using System;


 2 using System.Collections.Generic;


 3 using System.Linq;


 4 using System.Text;


 5 using System.Web.UI.WebControls;


 6 using System.Web.UI;


 7 using System.ComponentModel;


 8 using System.Web;


 9 


 10 namespace mydream.Controls


 11 {


 12 [ToolboxData("<{0}:SmartDropDownList runat=server></{0}:SmartDropDownList>")]


 13 public class SmartDropDownList : DropDownList


 14 {


 15 /// <summary>


 16  /// 构造函数


 17  /// </summary>


 18  public SmartDropDownList() { }


 19 


 20 /// <summary>


 21  /// 将控件的内容呈现到指定的编写器中


 22  /// </summary>


 23  /// <param name="writer"></param>


 24  protected override void RenderContents(HtmlTextWriter writer)


 25 {


 26 OptionGroupRenderContents(writer);


 27 }


 28 


 29 /// <summary>


 30  /// 呈现Option或OptionGroup


 31  /// </summary>


 32  /// <param name="writer">writer</param>


 33  private void OptionGroupRenderContents(HtmlTextWriter writer)


 34 {


 35 // 是否需要呈现OptionGroup的EndTag


 36  bool writerEndTag = false;


 37 


 38 foreach (ListItem li in this.Items)


 39 {


 40 // 如果没有optgroup属性则呈现Option


 41  if (li.Value != this.OptionGroupValue)


 42 {


 43 // 呈现Option


 44  RenderListItem(li, writer);


 45 }


 46 // 如果有optgroup属性则呈现OptionGroup


 47  else


 48 {


 49 if (writerEndTag)


 50 // 呈现OptionGroup的EndTag


 51  OptionGroupEndTag(writer);


 52 else


 53 writerEndTag = true;


 54 


 55 // 呈现OptionGroup的BeginTag


 56  OptionGroupBeginTag(li, writer);


 57 }


 58 }


 59 


 60 if (writerEndTag)


 61 // 呈现OptionGroup的EndTag


 62  OptionGroupEndTag(writer);


 63 }


 64 


 65 /// <summary>


 66  /// 呈现OptionGroup的BeginTag


 67  /// </summary>


 68  /// <param name="li">OptionGroup数据项</param>


 69  /// <param name="writer">writer</param>


 70  private void OptionGroupBeginTag(ListItem li, HtmlTextWriter writer)


 71 {


 72 writer.WriteBeginTag("optgroup");


 73 


 74 // 写入OptionGroup的label


 75  writer.WriteAttribute("label", li.Text);


 76 


 77 foreach (string key in li.Attributes.Keys)


 78 {


 79 // 写入OptionGroup的其它属性


 80  writer.WriteAttribute(key, li.Attributes[key]);


 81 }


 82 


 83 writer.Write(HtmlTextWriter.TagRightChar);


 84 writer.WriteLine();


 85 }


 86 


 87 /// <summary>


 88  /// 呈现OptionGroup的EndTag


 89  /// </summary>


 90  /// <param name="writer">writer</param>


 91  private void OptionGroupEndTag(HtmlTextWriter writer)


 92 {


 93 writer.WriteEndTag("optgroup");


 94 writer.WriteLine();


 95 }


 96 


 97 /// <summary>


 98  /// 呈现Option


 99  /// </summary>


100  /// <param name="li">Option数据项</param>


101  /// <param name="writer">writer</param>


102  private void RenderListItem(ListItem li, HtmlTextWriter writer)


103 {


104 writer.WriteBeginTag("option");


105 


106 // 写入Option的Value


107  writer.WriteAttribute("value", li.Value, true);


108 


109 if (li.Selected)


110 {


111 // 如果该Option被选中则写入selected


112  writer.WriteAttribute("selected", "selected", false);


113 }


114 


115 foreach (string key in li.Attributes.Keys)


116 {


117 // 写入Option的其它属性


118  writer.WriteAttribute(key, li.Attributes[key]);


119 }


120 


121 writer.Write(HtmlTextWriter.TagRightChar);


122 


123 // 写入Option的Text


124  HttpUtility.HtmlEncode(li.Text, writer);


125 


126 writer.WriteEndTag("option");


127 writer.WriteLine();


128 }


129 


130 /// <summary>


131  /// 用于添加SmartDropDownList的分组项的ListItem的Value值


132  /// </summary>


133  [


134 Browsable(true),


135 Description("用于添加DropDownList的分组项的ListItem的Value值"),


136 Category("扩展")


137 ]


138 public virtual string OptionGroupValue


139 {


140 get


141 {


142 string s = (string)ViewState["OptionGroupValue"];


143 


144 return (s == null) ? "optgroup" : s;


145 }


146 set


147 {


148 ViewState["OptionGroupValue"] = value;


149 }


150 }


151 }


152 }

smartDropDownList.aspx页面代码如下所示：

smartDropDownList.aspx

 1 <%@ Page Language="C#" AutoEventWireup="true" CodeFile="smartDropDownList.aspx.cs" Inherits="smartDropDownList" %>


 2 


 3 <%@ Register Assembly="Controls" Namespace="mydream.Controls" TagPrefix="cc1" %>


 4 


 5 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">


 6 


 7 <html xmlns="http://www.w3.org/1999/xhtml">


 8 <head runat="server">


 9 <title></title>


10 </head>


11 <body>


12 <form id="form1" runat="server">


13 <div>


14 <cc1:SmartDropDownList ID="SmartDropDownList1" runat="server">


15 </cc1:SmartDropDownList>


16 </div>


17 </form>


18 </body>


19 </html>

smartDropDownList.aspx页面smartDropDownList.cs如下所示：

smartDropDownList.cs

 1 using System;


 2 using System.Collections.Generic;


 3 using System.Linq;


 4 using System.Web;


 5 using System.Web.UI;


 6 using System.Web.UI.WebControls;


 7 using System.Data;


 8 


 9 public partial class smartDropDownList : System.Web.UI.Page


10 {


11 protected void Page_Load(object sender, EventArgs e)


12 {


13 if (!IsPostBack)


14 {


15 this.Bindddlist(this.SmartDropDownList1);


16 }


17 }


18 


19 /// <summary>


20  /// 板块ListItem


21  /// </summary>


22  /// <returns></returns>


23  private List<ListItem> GetBoardList()


24 {


25 List<ListItem> list = new List<ListItem>();


26 for (int i = 1; i < 6; i++)


27 {


28 ListItem li = new ListItem("这里是板块"+i,i.ToString());


29 list.Add(li);


30 }


31 return list;


32 }


33 


34 /// <summary>


35  /// 子板块ListItem


36  /// </summary>


37  /// <returns></returns>


38  private List<ListItem> GetSubBoardList()


39 {


40 List<ListItem> list=this.GetBoardList();


41 List<ListItem> list_sub = new List<ListItem>();


42 foreach (ListItem li in list)


43 {


44 ListItem li_sub = new ListItem("这一项是上一级的子板块", "这里是你像传递参数的值");


45 list_sub.Add(li_sub);


46 }


47 return list_sub;


48 }


49 


50 /// <summary>


51  /// 绑定下拉控件数据


52  /// </summary>


53  private void Bindddlist(mydream.Controls.SmartDropDownList smartddlist)


54 {


55 smartddlist.Items.Clear();


56 List<ListItem> list = this.GetBoardList();


57 foreach (ListItem li in list)


58 {


59 ListItem item = new ListItem("--" + li.Text, "optgroup");


60 smartddlist.Items.Add(item);


61 List<ListItem> list_sub = this.GetSubBoardList();


62 foreach (ListItem li_sub in list_sub)


63 {


64 smartddlist.Items.Add(li_sub);


65 }


66 }


67 smartddlist.DataBind();


68 }


69 }

你可以根据你数据库的设计来绑定值，这里没用数据库，只是说明思路！

源码下载，点击这里！

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