# 如何选择 OdDbBlockReference 中的特定实体（而非整个块引用）？

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选择子实体及更低层级元素的示例代码：

```plaintext
var opt = new tlib.OdTvSelectionOptions();
opt.setLevel(tlib.SelectionLevel.kSubentity);
opt.setMode(tlib.SelectionMode.kCrossing);

var selectionSet = viewer.activeView.select([0, 0, 1920, 1080], opt, viewer.getActiveModel());
var itr = selectionSet.getIterator();
```

for (; ! itr.done(); itr.step()) { var subEntity = itr.getSubEntity(); console.log('sub entity'); }