给图层添加新字段

arcengine二次开发如何给图层添加字段？
我自己的写法如下：
IField pField = new FieldClass();
IFieldEdit pFieldEdit = pField as IFieldEdit;
pFieldEdit.AliasName_2 = "与此要素重叠要素个数";
pFieldEdit.Name_2 = "Overlaps_count";
pFieldEdit.Type_2 = esriFieldType.esriFieldTypeDouble;
IClass pClass = pFeatureLayer.FeatureClass as IClass;
pClass.AddField(pField);
这样写最后一行代码会报错，说是com组件调用出错。