public class ClassFlag 

//Must be called on the MCT
//var pcsl = ...;
var filters = pcsl.GetFilters();
PointCloudFilterDefinition fdef = null;
if (filters.Count() == 0)
{
  fdef = new PointCloudFilterDefinition()
  {
    //7 is "edge of flight line" - exclude
    ClassFlags = new List<ClassFlag> { 
       new ClassFlag(7, ClassFlagOption.Exclude) }
  };
}
else
{
  fdef = PointCloudFilterDefinition.FromCIM(filters);
  //keep any include or ignore class flags
  var keep = fdef.ClassFlags.Where(
         cf => cf.ClassFlagOption != ClassFlagOption.Exclude).ToList();
  //7 is "edge of flight line" - exclude
  keep.Add(new ClassFlag(7, ClassFlagOption.Exclude));
  fdef.ClassFlags = keep;
}
//apply
pcsl.SetFilters(fdef.ToCIM());