既能输入又能选择的DropDownList控件

早就想做一个这样的控件了，最近在一个项目中遇到了这样的问题，所以就写了一个。

我遇到的需求是既能输入又能选择的DropDownList，其中输入的是课程成绩，选择的是补考、缓考、缺考。

此控件支持取值和赋值。支持IE6、IE7，其他的没测。

SelectTextBox.ascx

<style type="text/css">
.cls{
POSITION:absolute;
}
</style>
<div class="cls" style="WIDTH: 85px;z-index:100" align="center">
<iframe style="position:absolute;z-index:-1;width:expression(this.nextSibling.offsetWidth);height:expression(this.nextSibling.offsetHeight);top:expression(this.nextSibling.offsetTop);left:expression(this.nextSibling.offsetLeft);" frameborder="0" ></iframe>
<asp:TextBox ID="TextBox1" runat="server" Width="85px" Height="15px" OnTextChanged="TextBox1_TextChanged"></asp:TextBox>
</div>
<asp:DropDownList ID="DropDownList1" runat ="server" Width="107px" Height="20px" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" AutoPostBack="True" ></asp:DropDownList>

SelectTextBox.ascx.cs

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

namespace JKCollegeManage.WebPage.Score
{
public partial class SelectTextBox : System.Web.UI.UserControl
{
private string _text;
protected void Page_Load(object sender, EventArgs e)
{
}
// Text 重写了TextBox的Text属性
public String Text
{
get
{
_text = this.TextBox1.Text;
return _text;
}
set
{
this.TextBox1.Text = value;
_text = this.TextBox1.Text;
}
}

//为控件增加一个可选择的项
public void AddItem(String item)
{
this.DropDownList1.Items.Add(item);
}

//为控件增加一个可选择的项
public void AddItem(ListItem item)
{
this.DropDownList1.Items.Add(item);
}

//为控件增删除一个可选择的项
public void RemoveItem(ListItem item)
{
this.DropDownList1.Items.Remove(item);
}
//为控件增删除一个可选择的项
public void RemoveItem(String item)
{
this.DropDownList1.Items.Remove(item);
}

//清除控件数据
public void Clear()
{
this.DropDownList1.Items.Clear();
this.TextBox1.Text = "";
}
//返回选项数量
public int Count
{

get
{
return this.DropDownList1.Items.Count;
}

}

protected void TextBox1_TextChanged(object sender, EventArgs e)
{

}

//选择某项
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
this.TextBox1.Text = this.DropDownList1.SelectedItem.Text;
}

}
}