[MS C#] 关于ScanCriteria的使用问题

我想请问一下，我写了个方法，想得到一个范围内的元素， 

public static void GetElementsByRange(DgnModelRef refmodel, DRange3d range, ScanDelegate callback)
{
ScanCriteria scan = new ScanCriteria();
scan.SetModelRef(refmodel);
//scan.SetModelSections(DgnModelSections.GraphicElements);
ScanRange scanRange = new ScanRange((long)range.Low.X, (long)range.Low.Y, (long)range.Low.Z, (long)range.High.X, (long)range.High.Y, (long)range.High.Z);
scan.SetRangeTest(scanRange);
StatusInt status= scan.Scan(callback);

}

然后回调并没有被执行，是C# 里面有问题吗？
status我得到的是10，没有找到具体含义