How to Save datasource to be accessed after PostBack

Yes, you can save DataTable in Session Just Try

DataTable dt = new DataTable(); //Or What Ever Datatable you want

Session["tblData"] = dt;

// To retrieve it from session
DataTable dt = (DataTable)Session["tblData"];

I am storing session in database and not in memory. Having said that is storing in session ok?

Currently there may be 100 users in a day. But the plan is too increase and support. I want to write a website that will be scalable and not have to worry about this in the future. Please suggest. Thanks

IS there any disadvantage of caching? Like memory?

Of course, caching uses memory, so overusing it can affect memory. If you describe your scenario more, I can help you with the design better.

I am developing an eCommerce website. ASP.NET/VB.NET 2010/SQL Server 2008.

The users can search for products. The search in some cases may return about 5000 records or more. The viewstate increases > 4MB in that case. One option for me would be to limit the records resultset to <1000. If I dont want to do that then I want to know what would be the best way to handle the records that are returned from the db.

Currently I have disabled the Viewsource in the page so the page does not crash after >5000 records.
Then how do I do paging sorting etc. Should I save the results in Session/Cache or do SQL paging (return only records that are displyed) and fetch the records everytime from the db.

Please help. Thanks