Have you tried this:
if (primaryViewId != ElementId.InvalidElementId)
Question
if (ElementId.op_Inequality(primaryViewId, ElementId.InvalidElementId))
Error: 'Autodesk.Revit.DB.ElementId.operator !=(Autodesk.Revit.DB.ElementId, Autodesk.Revit.DB.ElementId)': cannot explicitly call operator or accessor
Solution
Have you tried this:
if (primaryViewId != ElementId.InvalidElementId)