使用自定义控件创建可编辑下拉框

aaronbai

于 2007-10-13 16:49:00 发布

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分类专栏： ASP.NET(C#) 文章标签： string server output module system class

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本文介绍如何在ASP.NET中创建一个可编辑的下拉框控件，通过自定义控件实现文本框与下拉列表的结合，允许用户直接输入或选择列表项。

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目的：创建可编辑（可输入）下拉框

步骤一：在VS2005中新建WEB 控件库 WebControlLibrary1

步骤二：建立自定义控件类DropDownListExtend

using System;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.ComponentModel;

using System.Collections;

namespace WebControlLibrary1

{

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

public class DropDownListExtend : System.Web.UI.WebControls.TextBox

{

private Hashtable _values;

private DropDownList _DropDownList;

public Hashtable Values

{

get { return _values; }

set { _values = value; }

}

public DropDownListExtend()

{

_values = new Hashtable();

_DropDownList = new DropDownList();

}

protected override void Render(HtmlTextWriter output)

{

int iWidth = Convert.ToInt32(base.Width.Value);

if (iWidth == 0)

{

iWidth = 102;

base.Width = Unit.Parse("102px");

}

int sWidth = iWidth + 16;

int spanWidth = sWidth - 18;

output.Write("<div style="POSITION:relative">");

output.Write("<span style="MARGIN-LEFT:" + spanWidth.ToString() + "px;OVERFLOW:hidden;WIDTH:18px">");

_DropDownList.Width = Unit.Parse(sWidth.ToString() + "px");

_DropDownList.Style.Add("MARGIN-LEFT", "-" + spanWidth.ToString() + "px");

_DropDownList.ID = base.ID + "_Select";

_DropDownList.Attributes.Add("onchange", "this.parentNode.nextSibling.value=this.value");

_DropDownList.Attributes.Add("onfocus", "" + this.getFocusScript() + "");

if (_values.Count > 0)

{

foreach (string key in _values.Keys)

{

ListItem item = new ListItem();

item.Value = _values[key].ToString();

item.Text = key;

_DropDownList.Items.Add(item);

}

}

_DropDownList.RenderControl(output);

output.Write("</span>");

base.Style.Clear();

base.Width = Unit.Parse(iWidth.ToString() + "px");

base.Style.Add("left", "0px");

base.Style.Add("POSITION", "absolute");

base.Render(output);

output.Write("</div>");

}

private string getFocusScript()

{

string strScript = " ";

strScript += "var isExist = -2; ";

strScript += "var obj = event.srcElement; ";

strScript += "var str = this.parentNode.nextSibling.value; ";

strScript += "var ary = obj.options; ";

strScript += "for(var i=0;i<ary.length;i++){ ";

strScript += " if(str == ary[i].text){ ";

strScript += " isExist = i; ";

strScript += " break; ";

strScript += " } ";

strScript += "} ";

strScript += "if(isExist != -2){ ";

strScript += " obj.selectedIndex = isExist; ";

strScript += "} ";

strScript += "else{ ";

strScript += " obj.selectedIndex = -1; ";

strScript += "} ";

return strScript;

}

}

}

步骤三：编译工程，生成跟WEB控件库工程名字一样的DLL，如WebControlLibrary1.dll

步骤四：在需要使用下拉框的工程添加应用（就是在其BIN目录里添加WebControlLibrary1.dll）

步骤五：具体应用：

页面代码如下：

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

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" >

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

<head runat="server">

<title>无标题页</title>

</head>

<body>

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

<div>

<EditDDLPreFix:DropDownListExtend ID="EditableDDL" runat="server" Text="text" Width="93px"></EditDDLPreFix:DropDownListExtend>

</form>

</body>

</html>

CS文件如下：

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;

public partial class Module_DataManage_MasterPage : System.Web.UI.Page

{

public Hashtable values;

protected void Page_Load(object sender, EventArgs e)

{

values = new Hashtable();

values.Add("a", "a");

values.Add("b", "b");

values.Add("c", "c");

this.EditableDDL.Values=values;

}

public Hashtable Values {

get { return values; }

set { values = value; }

}

}

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