Hi, 

I'm not exactly sure what you're asking. Assuming you have AutoGenerateColumns set to true (which it is by default) the xamgrid will find your IEnumerable properties and automatically make ColumnLayouts for them which will result in a hierarchy for you. 

You can also manually define the hierachy though if you don't want it to be generated in which case you need to add ColumnLayout objects to your Column's collection, where the key of the columnlayout corresponds to the property in you underlying data that is your ObservableCollection. 

We have a sample in our Samples browser that shows this: 

http://samples.infragistics.com/sllob/RunSamples.aspx?cn=grid#/grid/hierarchical-data

-SteveZ