private void ExplodeBlock()
    {
        // 与用户交在图面上选择要打碎的块引对象
        MxDrawUtility mxUtility = new MxDrawUtility();
        object getPt;
        MxDrawEntity ent = mxUtility.GetEntity(out getPt,"n 选择图块:");

        if (ent == null)
        {
            MessageBox.Show("没有选择实体..");
            return;
        }

        if (ent is MxDrawBlockReference)
        {
            // 选择的是一个块对象，就调用打碎函数碎
            MxDrawBlockReference blkRef = (MxDrawBlockReference)ent;
            MxDrawResbuf rb = (MxDrawResbuf)(blkRef.Explode() );

            // 得到打碎后新生成的实体的id
            for(Int32  i = 1; i < rb.Count;i++)
            {
                long entId = rb.AtLong(i);
            }
        }
    }