I have been working in a .NET Framework 4 project using server tags like &lt;%=whatever %&gt; to set the visibility of runat=&quot;server&quot; controls, like the following:

      &lt;div id=&quot;MyId&quot; runat=&quot;server&quot; visible=&quot;&lt;%=MyVisiblePropertyOnCodeBehind %&gt;&quot; &gt;
        Content
      &lt;/div&gt;

This works on framework 4, but now trying to use this on a Framework 3.5 project it doesn&#39;t seems to work. Is this a Framework 4 only feature? Is there a coolest (and .aspx side) alternative to setting the visibility from codebehind? I&#39;m using the ugly:

        MiId.Visible = MyVisiblePropertyOnCodeBehind

Thanks in advance,

Tom


**[EDITED] SOLUTION:**

Thanks for your comments that makes me understand my problem and the solution!

It was my fault in more than one thing. 

In the VS2010 project we were using &lt;%# instead of &lt;%=  

Also, I didn’t notice that in the VS2010 project we were using pages inherited not from “Page”, but from a CustomPage class, that was making the binding automatically, without me noticing it, and that makes me think that was a Framework 4.0 only feature.

As you told here, if you have the following markup:

      &lt;div id=&quot;MyId&quot; runat=&quot;server&quot; visible=&quot;&lt;%# MyVisiblePropertyOnCodeBehind %&gt;&quot; &gt;
        Content
      &lt;/div&gt;

you can make it work, adding the following to the codebehind:

        public bool  MyVisiblePropertyOnCodeBehind = true;
        protected void Page_Load(object sender, EventArgs e) {
            DataBind();
            // Or if you want only for one control, MyId.DataBind();             
        }


As I read, this DataBind() can reduce performance of the application. Do you have idea of how much? Could this be understood as a “professional” technique to be used on big projects, or do you think it should be avoided?

I love the way it makes markup  readable and  easy to understand in a single view, but I wouldn’t like to be guilty of slow code because that.

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Set Visible property with server tag <%= %> in Framework 3.5