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扩展DropDownList控件和ListBox控件(1) - 支持分组功能(optgroup标签)
作者： webabcd
介绍
扩展DropDownList控件和ListBox控件：
通过 DropDownList控件和ListBox控件的.Items.Add(ListItem item)方法，来为其添加optgroup标签，从而实现分组功能
使用方法
1、设置属性：
OptionGroupValue - 用于添加DropDownList(ListBox)控件的分组项的ListItem的Value值（默认为optgroup）
2、使用DropDownList(ListBox)控件的.Items.Add(ListItem item)方法：
OptionGroupValue为默认值时：SmartDropDownList.Items.Add(new ListItem("中国", "optgroup"));
图示
关键代码（以DropDownList为例）
SmartDropDownList.cs
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); } }
}
Property.cs
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; } } }}
OptionGroup.cs
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(); } }}
OK
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