.net复合控件之 可输入的下拉控件

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Collections;

namespace QC_Control
{
/// <summary>
/// 自定义可输入下拉框类
/// </summary>
[ToolboxData("<{0}:CustomInputDropdownControl runat=server></{0}:CustomInputDropdownControl>")]
public class CustomInputDropdownControl : TextBox
{

private DropDownList ddlListItem = new DropDownList(); //下拉框
private TextBox TxtBox = new TextBox();
private Hashtable _values = new Hashtable(); //用于绑定下拉框框的值

/// <summary>
/// 键值引用变量set/get封装方法
/// </summary>
public Hashtable Item
{
get {
if (ViewState["Values"] == null)
{

ViewState["Values"] = new Hashtable();

}
else { }

Hashtable s = (Hashtable)ViewState["Values"];
return s;
}
set { ViewState["Values"] = value; }
}


/// <summary>
/// default constructor
/// initialization DropDownList and Hashtable instance variable
/// </summary>
public CustomInputDropdownControl()
{
// this._values = new Hashtable();
// this.ddlListItem = new DropDownList();
}

/// <summary>
/// 重写控件类Render方法体
/// </summary>
/// <param name="output"></param>
protected override void Render(HtmlTextWriter output)
{ ddlListItem.ID ="Ddl"+ base.ID;
TxtBox.ID ="Txt"+ base.ID;
// 框架的开始
output.Write("<table cellspacing='0' cellpadding='0' border='0'><tr><td align='left'><span style='position:absolute;border:1pt solid #c1c1c1;overflow:hidden;width:188px;height:19px;clip:rect(-1px 190px 190px 170px);'>");

//此处之所以用clientID是因为当在卡片选项时,.net程序会将base.ID自动命名名字
ddlListItem.Attributes.Add("onChange", getFocusValue(TxtBox.ID, ddlListItem.ID));
ddlListItem.Attributes.Add("style", "width:190px;height:23px;margin-top:-2px;");
TxtBox.Attributes.Add("style", "width:170px;height:15px;border:0pt;");
//遍历数据到下拉框对象中
if (this.Item.Count > 0)
{
foreach (string key in Item.Keys)
{
ListItem item = new ListItem();
item.Value = key;
item.Text = Item[key].ToString();
ddlListItem.Items.Add(item);
}
}
ddlListItem.RenderControl(output);
output.Write("</span><span style='position:absolute;border-top:1pt solid #c1c1c1;border-left:1pt solid #c1c1c1;border-bottom:1pt solid #c1c1c1;width:170px;height:19px;'>");
TxtBox.RenderControl(output);
// 框架的结尾
output.Write("</span> </td></t></table>");
}

//响应事件方法
public string getFocusValue(string TxtId,string ddlId)
{
return "javas"+"cript:"+"document.getElementById('" + TxtId + "').value=document.getElementById('" + ddlId + "').options[document.getElementById('" + ddlId + "').selectedIndex].value;".ToString();

}
}
}