iis - IIS Script Time-out not reading the value programmatically

Question

the ASP (classic) page is reading huge number of records from a SQL Server Table which takes a while so we need to set the Script time-out to at least 300 seconds or 5 minutes.

the issue is when I set the Script time-out value from IIS Manager it works fine, but when I try to set the value programmatically it is NOT working , here is the code I am using :

     <% Server.ScriptTimeout = 300 %> 

Environment : ASP.Net 2.0 | Windows 7 | SQL Server 2008 R2

Note : issue is not about sql server query.

is there any file or other setting that is causing the IIS not to read the ScriptTimeout value ?