private const string scp_number_only_script_id="{29fd7a41-49fd-4fc4-afa9-6a0b875a1a51}";
private const string scp_number_only_hook="return virty(this);";
private const string scp_number_only_script=
"<script language=\"javascript1.2\">\nfunction virty (ctrl)\n{{\n"+
"if (event.keycode == 13)\n return true;\n if (event.keycode < 48 || event.keycode > 57)\n return false;\n else\n return true;\n}}"+
"</script>"; 

     下面的方法用于验证代码的生成：

private void renderjavascript()
...{
if(!page.isclientscriptblockregistered(scp_number_only_script_id)) page.registerclientscriptblock(scp_number_only_script_id,string.format(scp_number_only_script,base.id));
}

    为什么会有page.isclientscriptblockregistered(scp_number_only_script_id)呢？我们想象一下，如果在web页中有十个该控件，那是不是就要输出十个这样的脚本？显然，这是画蛇添足了，所以，我们要用isclientscriptblockregistered（）判断该脚本是否在客户端输出，如果脚本在客户端已注册，则不再输出了。

    接下来就是重写onprerender()方法了，该方法负责向客户端绘制脚本。

    大家应该注意到，该脚本需要事件触发才会执行，当用户从浏览器输入数据时，如果是非数字，则忽略该动作，否则才接受输入。这就需要onkeypress="javascript:return virty(this);"这段代码了。那么，这段代码怎么向客户端输出呢？重写addattributestorender（）方法吧，该方法负责绘制组件的属性。于是，我们写了下面一段代码：

protected override void addattributestorender(htmltextwriter writer)
...{
base.addattributestorender(writer);
writer.addattribute("onkeypress",scp_number_only_hook);
}

    最后的源码如下：

最后代码#region 最后代码
using system;

using system.text;

using system.drawing;

using system.web;

using system.web.ui;

using system.web.ui.webcontrols;

namespace powerasp.net.controls

...{

[toolboxbitmap(typeof(numbereditor),"powerasp.net.controls.numbereditor.bmp")]

public class numbereditor:baseeditor

...{

private const string scp_number_only_script_id="{29fd7a41-49fd-4fc4-afa9-6a0b875a1a51}";

private const string scp_number_only_hook="return numbereditor_keypress_handle(this);";

private const string scp_number_only_script=

"<script language=\"javascript1.2\">\nfunction numbereditor_keypress_handle(ctrl)\n{{\n"+

"if (event.keycode == 13)\n return true;\n if (event.keycode < 48 || event.keycode > 57)\n return false;\n else\n return true;\n}}"+

"</script>";

//rending number-limit javascript. 

private void renderjavascript()

...{

if(!page.isclientscriptblockregistered(scp_number_only_script_id)) page.registerclientscriptblock(scp_number_only_script_id,string.format(scp_number_only_script,base.id));

}

protected override void addattributestorender(htmltextwriter writer)

...{

base.addattributestorender(writer);

writer.addattribute("onkeypress",scp_number_only_hook);

}

protected override void onprerender(eventargs e)

...{

base.onprerender (e);

renderjavascript();

}

public numbereditor():base()

...{

}

}

}
#endregion