My webservice is returning an array of data like so (obviously there's much more data)

[
  {
    "children": null,
    "id": "95813",
    "parent": "-1",
    "orgName": "ABC",
    "total": 224422,
    "bad": 4898
  },
  {
    "children": null,
    "id": "55728",
    "parent": "95813",
    "orgName": "DEF",
    "total": 1146,
    "bad": 7
  }
]

You can see that the parent of the second item identified the ID of the first item.  In the HTML I used this code to represent that data:

<igx-tree-grid #treeGrid [data]="data" childDataKey="children" [autoGenerate]="false" [allowFiltering]="true">
  <igx-column field="orgName" title="Org Name" dataType="string"></igx-column>
  <igx-column field="total" title="Total" dataType="number" [filterable]="false"></igx-column>
  <igx-column field="bad" title="Not Compliant" dataType="number" [filterable]="false"></igx-column>
  <igx-column field="percent" title="Percent" datatype="number" [filterable]="false"></igx-column>
</igx-tree-grid>

When the grid displays though, both those items are toplevel, one isn't inserted under the other.