title: Cross Postback from Masterpage
body: <p>I have a textbox used to search for products. This textbox is placed in the site's masterpage.
  However, I'm getting a null error for the frmSearch value once posted back.</p>
  
  <p>masterpage search:</p>
  
  <pre><code>&lt;asp:TextBox ID="frmSearch" runat="server" CssClass="searchbox"&gt;&lt;/asp:TextBox&gt;
  &lt;asp:LinkButton ID="searchGo" CssClass="searchbutton" PostBackUrl="search.aspx"  runat="server"&gt;GO&lt;/asp:LinkButton&gt;
  </code></pre>
  
  <p>search.aspx pageload:</p>
  
  <pre><code>if (PreviousPage != null &amp;&amp; PreviousPage.IsCrossPagePostBack)
          {
              Page previousPage = PreviousPage;
              TextBox tbSearch = (TextBox)PreviousPage.FindControl("frmSearch");
              searchValue.Text = for tbSearch.Text;
          }
  </code></pre>
  
  <p>Where am I going wrong?</p>