需求：要求DropDownList控件支持文本输入方式快速定位选择项。输入文本后按Tab键或Enter键触发SelectedIndexChanged事件。

Code：

using System;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Configuration;

namespace Com.Elong.Commission.WebControl
{
///

/// DropDownListExtend 的摘要说明。
///

[DefaultProperty("Text"),
ToolboxData("<{0}:DropDownListExtend runat=server>")]
public class DropDownListExtend : System.Web.UI.WebControls.DropDownList,INamingContainer
{
private string NEWLINE = System.Environment.NewLine;

public TextBox _TextBox;

public DropDownListExtend()
{
_TextBox = new TextBox();
}

[Bindable(true),
Category("Appearance"),
DefaultValue("")]
public string Text
{
get
{
return _TextBox.Text;
}

set
{
_TextBox.Text = value;
}
}

///

/// 将此控件呈现给指定的输出参数。
///

/// 要写出到的 HTML 编写器
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 + 0;
int spanWidth = sWidth - 18;

output.Write("

");

WriteJSFunc(output);
}

private void WriteJSFunc(HtmlTextWriter output)
{
string jsFileURL = System.Configuration.ConfigurationSettings.AppSettings["WebControlJS"];
output.Write("");
}

////////////////采用外部javascript 文件连接，以增强可用性和维护性////////
///
// private void WriteJSFunc(HtmlTextWriter output)
// {
// output.Write("");
// }

// private void WriteKeyDownFunc(HtmlTextWriter output)
// {
// output.Write("function document.onkeydown() " + NEWLINE);
// output.Write("{" + NEWLINE);
// output.Write("if (event.keyCode == 13) " + NEWLINE);
// output.Write("{" + NEWLINE);
// output.Write("var e = event.srcElement; " + NEWLINE);
// output.Write(" if (e.tagName == "INPUT" && e.type == "text") " + NEWLINE);
// output.Write("event.keyCode = 9; " + NEWLINE);
// output.Write("} " + NEWLINE);
// output.Write("}" + NEWLINE);
// }

// private void WriteDoSelect(HtmlTextWriter output)
// {
// output.Write("function doSelect() " + NEWLINE);
// output.Write("{ " + NEWLINE);
// output.Write("var ddl = document.getElementById("" + base.UniqueID + "");" + NEWLINE);
// output.Write("var count = ddl.options.length;" + NEWLINE);
// output.Write("var selValue = document.all('" + this._TextBox.UniqueID +"').value;" + NEWLINE);
// output.Write("for (var i=0;i// output.Write(" {" + NEWLINE);
// output.Write("if (ddl.options[i].text == selValue) " + NEWLINE);
// output.Write(" {" + NEWLINE);
// output.Write("ddl.options[i].selected = true;" + NEWLINE);
// output.Write("return;" + NEWLINE);
// output.Write(" }" + NEWLINE);
// output.Write(" }" + NEWLINE);
// output.Write(" alert('没找到查找项');" + NEWLINE);
// output.Write(" document.all('" + this._TextBox.UniqueID +"').value = ddl.options[0].text;" + NEWLINE);
// output.Write("}" + NEWLINE);
// }

}
}

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