This is the database structure you should to use: http://www.telerik.com/help/aspnet-ajax/gantt-data-binding-database-structure.html
You will have to create two tables - one for the tasks and one for the dependencies. Be sure that your database is compatible with the gantt. The official demo which uses SqlDataSources can be seen here: http://demos.telerik.com/aspnet-ajax/gantt/examples/overview/defaultcs.aspx#qsf-demo-source
Sample project with Database is can be downloaded from here
I hope this helps.
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