how to connect to a same local database used in domain database, when domain database is offline.(C# asp.net)

I am new to C#. I am doing an application for an institute registration,fees Payment etc. In my project i am using both windows and web application of C#.When i click a button from my windows form an asp page is opened in a browser. The rest of project is done as website. My question is,I am using a domain server as my database but when there is no current(offline) i want to use the same database in local system.Is there any option to do this? Please help me.........Thanks in advance. I am using C# version 2008 and MS SQL 2005.