Creating and Deleting Hidden Fields in SPList

Creating :
id = sourceList.Fields.Add("SourceRefId", SPFieldType.Guid, false);
SPField field = sourceList.Fields[id];
field.Hidden = true;
field.ReadOnlyField = true;
field.Update();
sourceList.Update();





Deleting
SPField field = sourceList.Fields["SourceRefId"];
field.Hidden = false;
field.ReadOnlyField = false;

field.Update();
sourceList.Fields.Delete("SourceRefId");