How do I save data with Infragistics grid ?

[ando]

Hi,
I've just got started with Infragistics, and encountered some problem on using Ultrawebgrid.
I only need data edited in the grid to be saved to its datasource.
Notice that I have taken care about setting some properties like : allowUpdate, allowAddNew ... on true.
But when I add, update or remove a row in the grid, it doesn't take effect to its datasource !
I use a collection object as datasource for the grid.

Thanks and regards.
Ando.