In COM, you need to create a Find condition InwOpFindSpec and assign it to the new selectionset by InwOpSelectionSet2.ImplicitFindSpec. Following is a demo code:
void AddSearchSelectionSet()
{
// get state object
ComApi.InwOpState oState =
ComBridge.State;
// new a selection set
ComApi.InwOpSelectionSet2 oNewSelSet =
(ComApi.InwOpSelectionSet2)(object)
oState.ObjectFactory(
ComApi.nwEObjectType.eObjectType_nwOpSelectionSet);
oNewSelSet.name = "MySet";
// create the find condition
ComApi.InwOpFindSpec nwFindSpec =
(ComApi.InwOpFindSpec)(object)
oState.ObjectFactory(
ComApi.nwEObjectType.eObjectType_nwOpFindSpec);
ComApi.InwOpFindCondition nwFindCondition =
(ComApi.InwOpFindCondition)(object)
oState.ObjectFactory(
ComApi.nwEObjectType.eObjectType_nwOpFindCondition);
nwFindCondition.SetAttributeNames("",
"Entity Handle");
nwFindCondition.SetPropertyNames("",
"Value");
nwFindCondition.Condition =
ComApi.nwEFindCondition.eFind_EQUAL;
nwFindCondition.value = "187E2";
nwFindSpec.selection = null;
nwFindSpec.SearchMode =
ComApi.nwESearchMode.eSearchMode_ALL_PATHS;
nwFindSpec.Conditions().Add(nwFindCondition);
// set the find condition to the selectionset
oNewSelSet.ImplicitFindSpec = nwFindSpec;
// add the selectionset to the collection
oState.SelectionSets().Add(oNewSelSet);
}