Crystal report clear memory

Class System.GC   use,Report Big size

GC.Collect(); //clear memory this.cryRptCard.ReportSource = null; //clear crystal report viewer this.cryRptCard.RefreshReport(); this._rptPrintCardLabel.SetDataSource(dt); this.cryRptCard.ReportSource = this._rptPrintCardLabel; GC.Collect();//clear memory