Performing complex grid operations such as Inserting, Deleting, Updating, Hierarchy relations, Grouping, Exporting, Paging, Sorting, Filtering, etc. require accommodating appropriate database operations. Therefore, we suggest you to avoid Simple Databinding and strongly recommend the use of more advanced databinding methods, which automatically handle the aforementioned functions:
Declarative DataSource (DataSourceID property)
Programmatic Data Binding (NeedDataSource event, + DetailTableDataBind for hierarchy). You should set the DataSource property ONLY within these event handler.
In your case passing the raw database within the NeedDataSource event should be enough. RadGrid will apply the filter and sorting expressions accordingly and extract the necessary items automatically.