WPF: DataGrid with a tree-column in an MVVM Windows application -

here rephrased version of issue:

here screenshot of result i'm looking (from older, non c#/wpf version of application):

looks other grid-tree-views , objectlistview provides. unfortunately have rules have follow:

• wpf
• mvvm
• just datagrid , components must used (no treeview, listview, etc.)
• the items hold in observablecollection<t> t.property1, t.property2 etc hold data columns of datagrid.
• the lower levels of item hold in t.propertychilds of type observablecollection<t> , not known/filled beforehand. must loaded on first exand of item.

here screenshot of similar data , i've got far in wpf/c#:

it looks standard datagrid. columns can hold, property of t columns showing, columns visible, etc defined own framework around datagrid adds columns public observablecollection<datagridcolumn> columns collection of system.windows.controls.datagrid.

my task new class derived datagridcolumn can display , load hierarchical data structure of viewmodel described above.

the main problems i'm facing far can tell: - how visibly display levels treeview in datagrid column - how process loaded data childs shown in first screenshot above. have flat observablecollection<t> add loaded childdata , properties level , parent - or possible define kindo of hierarchical data template datagrid?

thanks lot soko