private void timer1_Tick(object sender, EventArgs e)        {            DianGe dg = new DianGe();            dg.diange[i] = new ShuXing();            if (axWindowsMediaPlayer1.Ctlcontrols.currentPositionString.Equals(axWindowsMediaPlayer1.currentMedia.durationString))            {                dg.diange[i].zhuangTai = -1;                i++;                BoFang(dg.diange[i].geMing, dg.diange[i].geShou);                dg.diange[i].zhuangTai = 1;            }        }IF条件这里说未将对象引用设置到对象的实例。
该怎么破