How to get properties by category

hi~

I want to get properties by category. Just like the title in the picture below to classify and export. But only the customized ones that I export can not be exported by clicking here. The circles in the picture are uniformly assigned to "BREP cells". How to classify each class?

Here is my code. Thank you very much.

code：

 
            IEnumerator<Element> iEe = dgnModel.GetGraphicElements().GetEnumerator();
            iEe.Reset();
            while (iEe.MoveNext())
            {
                Element elTmp = iEe.Current;
                LogLine = string.Format("ElementId : {0}  ClassType : {1}  ElemenType : {2}  ElemenTypeName : {3}", elTmp.ElementId.ToString(), elTmp.GetType().ToString(), elTmp.ElementType, elTmp.TypeName);
                WriteLogLine(LogLine);
                Element myElem = dgnModel.FindElementById((ElementId)elTmp.ElementId);
                if(myElem ==null)
                {
                    
                }
                DgnECManager ecManager = DgnECManager.Manager;
                int count = 0;
                DgnECInstanceCollection instCol = ecManager.GetElementProperties(myElem, ECQueryProcessFlags.SearchAllClasses);
                foreach (IDgnECInstance inst in instCol)
                {
                    count++;
                    
                    LogLine = "----ECInstance" + count.ToString() + "[" + inst.ClassDefinition.DisplayLabel + "]";
                    WriteLogLine(LogLine);
                    IEnumerator<IECProperty> propertyEnum = inst.ClassDefinition.GetEnumerator();
                    while (propertyEnum.MoveNext())
                    {
                        IECPropertyValue propertyValue = inst.GetPropertyValue(propertyEnum.Current.Name);
                        if (propertyValue.IsArray)
                        {
                            IECArrayValue arrayVal = propertyValue as IECArrayValue;
                            if (arrayVal.Count >= 1)
                                propertyValue = arrayVal[0];
                        }
                        string strVal;
                        double dblVal;
                        int intVal;
                        var a = propertyValue.Type;
                        if (propertyValue.TryGetStringValue(out strVal))
                        {
                            LogLine = "\tProperty=" + propertyEnum.Current.DisplayLabel + ", stringValue=" + strVal;
                            WriteLogLine(LogLine);
                            //LogLine = UnicodeToString("u53c2");
                            //WriteLogLine(LogLine);
                        }
                        else if (propertyValue.TryGetDoubleValue(out dblVal))
                        {
                            LogLine = "\tProperty=" + propertyEnum.Current.DisplayLabel + ", doubleValue=" + dblVal.ToString();
                            WriteLogLine(LogLine);
                        }

                        else if (propertyValue.TryGetIntValue(out intVal))
                        {
                            LogLine = "\tProperty=" + propertyEnum.Current.DisplayLabel + ", intValue=" + intVal.ToString();
                            WriteLogLine(LogLine);
                        }
                            
                    }
                }