TextArea value in C#

Hi,
 
I have an HTML element defined as :
 

<textareaid="txtOrdersNotResult"runat="server"rows="5"cols="15"visible="false"></textarea>

 
when certain condition hold true, it triggers the textarea to be visible. Then it should set a value in this area, like
 

txtOrdersNotResult.Value = "this is a test"

 
I have also tried,

txtOrdersNotResult.InnerText = doesnotexist.ToString();

 
this area is empty.
 
any ideas?