How to get a surface normal in the assembly context ? - user selected surface.

I am making a journal that orients a modeling view in an assembly when a user clicks on a planar surface - just one click operation -, but I'm stuck.
I used the following code to get a surface, which was on this site in VB and I converted to c#.
Although I can get a surface, it is NOT an occurrence but a prototype since its IsOccurrence property is "false" and, when I get the normal of the surface, it's not in the assembly context.
How can I get a surface occurrence without any additional user's operations ?
Any advice will be appreciated.

public static Selection.Response SelectPlanarFace(string prompt, out Face myPlanarFace,out Point3d cursor)
{
UI theUI = UI.GetUI();
string title = "Select a planar face";
Selection.SelectionScope scope = Selection.SelectionScope.WorkPartAndOccurrence;
Selection.SelectionAction selAction = Selection.SelectionAction.ClearAndEnableSpecific;
bool includeFeatures = false;
bool keepHighlighted = false;
Selection.MaskTriple[] selectionMask_array=new Selection.MaskTriple[1];
selectionMask_array[0].Type = UFConstants.UF_solid_type;
selectionMask_array[0].SolidBodySubtype = UFConstants.UF_UI_SEL_FEATURE_PLANAR_FACE;
TaggedObject selObj;
Selection.Response resp = theUI.SelectionManager.SelectTaggedObject
(prompt, title, scope, selAction,includeFeatures, keepHighlighted, selectionMask_array, out selObj, out cursor);
if (resp == Selection.Response.ObjectSelected || resp == Selection.Response.ObjectSelectedByName)
{
myPlanarFace = (Face)selObj;
return Selection.Response.Ok;
}
else
{
myPlanarFace=null;
return Selection.Response.Cancel;
}
}