asp.net - 我如何摆脱未声明的 __o ？

Question

我的母版页中有一些代码，用于设置包含一些上下文敏感信息的超链接

<%If Not IsNothing(Profile.ClientID) Then%>
<span class="menu-nav"> 
<a  target="_blank" 
    href=
"http://b/x.aspx?ClientID=<%=Profile.ClientID.ToString()%>&Initials=<%=Session("Initials")%>"       
    >
    Send
    <br />
    SMS
    <br />
</a>

</span>
<%End If %>

<span class="menu-nav"> <!-- Name __o is not declared Error is flagged here-->

现在问题似乎出在 href 部分。如果我删除动态代码，错误就会消失。谁能告诉我如何解决这个问题？

Answer 1

我找到了 answer在 .net 论坛上。它很好地解释了 ASP.Net 为什么会这样:

We have finally obtained reliable repro and identified the underlying issue. A trivial repro looks like this:

  <% if (true) { %>

  <%=1%>
  <% } %>
  <%=2%>   

In order to provide intellisense in <%= %> blocks at design time, ASP.NET generates assignment to a temporary __o variable and language (VB or C#) then provide the intellisense for the variable. That is done when page compiler sees the first <%= ... %> block. But here, the block is inside the if, so after the if closes, the variable goes out of scope. We end up generating something like this:

   if (true) { 
        object @__o;
        @__o = 1;
   }
   @__o = 2;

The workaround is to add a dummy expression early in the page. E.g. <%="" %>. This will not render anything, and it will make sure that __o is declared top level in the Render method, before any potential ‘if’ (or other scoping) statement.

另一种解决方案是简单地使用

<% response.write(var) %>

而不是

<%= var %>