With COM API, you could setup an InwOpSelection and add the paths which is the result of the find. And call State.CurrentSelection = your InwOpSelection. While in .NET API, current selection is exposed as a document part CurrentSelection. The highlighting objects is to change the selected items of CurrentSelection.
The code below shows the ways to highlight in COM and .NET.
using Autodesk.Navisworks.Api;
using ComApi = Autodesk.Navisworks.Api.Interop.ComApi;
using ComApiBridge = Autodesk.Navisworks.Api.ComApi;
// highlight objects
private void highlight()
{
Document oDoc =
Autodesk.Navisworks.Api.Application.ActiveDocument;
// assume we get two model items
ModelItem oItem1 =
oDoc.Models[0].RootItem.DescendantsAndSelf.
ElementAt<ModelItem>(1);
ModelItem oItem2 =
oDoc.Models[0].RootItem.DescendantsAndSelf.
ElementAt<ModelItem>(2);
// create ModelItemCollection
ModelItemCollection oSel_Net =
new ModelItemCollection();
oSel_Net.Add(oItem1);
oSel_Net.Add(oItem2);
// highlight by .NET API
oDoc.CurrentSelection.SelectedItems.CopyFrom(oSel_Net);
//highlight by COM API
ComApi.InwOpState10 state =
ComApiBridge.ComApiBridge.State;
ComApi.InwOpSelection comSelectionOut =
ComApiBridge.ComApiBridge.ToInwOpSelection(oSel_Net);
state.CurrentSelection = comSelectionOut;
}