可输入的DropDownList扩展控件(C#)
首先,建立一个名字为ExtendWebControls的C#用户自定义Web控件的工程
然后,添加一个DropDownList.cs文件,类型为Web自定义控件
添加如下代码到文件中即可,需要注意的是在引用中要添加System.Design和System.Drawing
然后,添加一个DropDownList.cs文件,类型为Web自定义控件
添加如下代码到文件中即可,需要注意的是在引用中要添加System.Design和System.Drawing
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using System;
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using System.Web.UI;
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using System.Web.UI.WebControls;
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using System.ComponentModel;
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using System.Web.UI.Design;
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using System.Collections;
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namespace ExtendWebControls
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{
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/// <summary>
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/// DropDownList 的摘要说明。
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/// </summary>
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[ToolboxData("<{0}:DropDownListExtend runat=\"server\" />")]
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public class DropDownListExtend : System.Web.UI.WebControls.TextBox
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{
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private Hashtable _values;
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public DropDownList _DropDownList;
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public DropDownListExtend()
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{
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_values = new Hashtable();
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_DropDownList = new DropDownList();
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}
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public Hashtable Values
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{
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get
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{
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return _values;
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}
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set
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{
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_values = value;
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}
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}
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/// <summary>
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/// 将此控件呈现给指定的输出参数。
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/// </summary>
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/// <param name="output"> 要写出到的 HTML 编写器 </param>
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protected override void Render(HtmlTextWriter output)
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{
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int iWidth = Convert.ToInt32(base.Width.Value);
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if(iWidth == 0)
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{
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iWidth = 102;
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base.Width = Unit.Parse("102px");
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}
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int sWidth = iWidth + 16;
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int spanWidth = sWidth - 18;
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output.Write("<div style=\"POSITION:relative\">");
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output.Write("<span style=\"MARGIN-LEFT:" + spanWidth.ToString() + "px;OVERFLOW:hidden;WIDTH:18px\">");
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_DropDownList.Width = Unit.Parse(sWidth.ToString() + "px");
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_DropDownList.Style.Add("MARGIN-LEFT", "-" + spanWidth.ToString() + "px");
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_DropDownList.Attributes.Add("onchange", "this.parentNode.nextSibling.value=this.value");
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if(_values.Count > 0)
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{
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foreach(string key in _values.Keys)
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{
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ListItem item = new ListItem();
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item.Value = key;
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item.Text = _values[key].ToString();
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_DropDownList.Items.Add(item);
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}
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}
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if(_DropDownList.Items.Count == 1)
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{
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ListItem item = new ListItem();
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item.Value = "";
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item.Text = " ";
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_DropDownList.Items.Add(item);
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_DropDownList.SelectedIndex = 1;
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}
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_DropDownList.RenderControl(output);
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output.Write("</span>");
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base.Style.Clear();
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base.Width = Unit.Parse(iWidth.ToString() + "px");
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base.Style.Add("left", "0px");
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base.Style.Add("POSITION", "absolute");
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base.Render(output);
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output.Write("</div>");
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}
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}
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}
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