[MSCE C#]请问没有textstyle的Dimension怎么通过代码去使用?

 如图,请问怎样通过代码去使用该DimensionStyle,

DimensionStyle dimStyle = DimensionStyle.GetByName(styleName, dgnFile);

CreateDimensionCallbacks callbacks = new CreateDimensionCallbacks(dimStyle,null, new Symbology(), lvlId, null);

DimensionElement oDim = new DimensionElement(dgnModel, callbacks, dimtype);

textstyle传入null会new异常