属性的读取应该先查询对应属性是否存在，否则会出错

body.HasUserAttribute("DB_PART_NO", NXObject.AttributeType.String, -1) 

获取体的属性的示范

/// <summary>
/// 获取体的编号
/// </summary>
protected string AskBodyName(Body body)
{
    string partNo = body.HasUserAttribute("DB_PART_NO", NXObject.AttributeType.String, -1) ? body.GetStringAttribute("DB_PART_NO"):"";
    string name = body.IsOccurrence ? body.OwningComponent.DisplayName : partNo;
    return name;
}