label==<span>
textbox==<input type=text >
button==<input type=submit >
linkbutton==<a>
imagebutton==<input type=image >
hyperlink==<a>
dropdownlist==<select>
listbox==<select>
datagrid==<table>
datalist==<table>
repeater 什么都不生成
checkbox==<input type=checkbox >
checkboxlist==<input type=checkbox>
radiobutton==<input type=radio >
radiobuttonlist==<input type=radio>
image==<img>
panel==<div>