asp.net 前台调用后台方法

帮忙看看,为什么调用不成功?应该怎样调用后台的方法,不想用ajax.
后台方法:
C# code:
[System.Web.Services.WebMethod]
public static string aa(string name)
{
if (name == "aa")
{
return "11";
}
else
{
return name;
}
}

前台代码:
HTML code:
<script language="JavaScript">
function myCallBack(result) {
alert(result);
}
function show()
{
PageMethods.aa("aa",myCallBack);
}
</script>

HTML code:
<input name="" onClick="javascript:show()" type="button" value="aa" />

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HTML code:

<input name="" onClick="javascript:alert('<%=aa() %>')"type="button" value="aa" />
试试这个看看

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后台是webservice啊，项目中添加引用webservice，调用就可以了啊

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ASPX
C# code

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