engiGetAggrTypex

public const string ifcenginedll = @"ifcengine.dll";

[DllImport(IFCEngineDLL, EntryPoint = "engiGetAggrTypex")]
public static extern void engiGetAggrTypex(int_t aggregate, out int_t aggregateType);    

using RDF;      //  include at least engine.cs within your solution

void WriteAttribute(Int64 ifcInstance, string attributeName, Int64 attributeType)
{
    switch  (attributeType) {
        case  ifcengine.sdaiAGGR:
            Int64 aggregate = 0;
            ifcengine.sdaiGetAttrBN(ifcInstance, attributeName, ifcengine.sdaiAGGR, out aggregate);
            if (aggregate != 0)
            {
                Int64 cnt = ifcengine.sdaiGetMemberCount(aggregate);
                for (Int64 i = 0; i < cnt; i++)
                {
                    Int64 aggregateType = 0;
                    ifcengine.engiGetAggrType(aggregate, out aggregateType);
                    switch (aggregateType) {
                        case  ifcengine.sdaiSTRING:
                            {
                                string value;
                                ifcengine.sdaiGetAggrByIndex(aggregate, i, ifcengine.sdaiUNICODE, out value);
                                ...
                            }
                            break;

                        ...

                        default:
                            break;
                    }
                }
            }
            break;

        ...

        default:
            break;
    }
}

void WriteAttributes(Int64 ifcInstance)
{
    Int64 ifcEntity = ifcengine.sdaiGetInstanceType(ifcInstance),
          attributeCnt = ifcengine.engiGetEntityNoArguments(ifcEntity);

    for (Int64 i = 0; i < attributeCnt; i++)
    {
        string attributeName = ifcengine.engiGetEntityArgumentName(ifcEntity, i);
        Int64 attributeType = 0;
        ifcengine.engiGetEntityArgumentType(ifcEntity, i, out attributeType);
        WriteAttribute(ifcInstance, attributeName, attributeType);
    }
}