private void simpleButton1_Click(object sender, EventArgs e) { DataRow drv = gridviewGrvList.GetFocusedDataRow(); if (drv["ReceiptID"]!= DBNull.Value) { int ReceiptID = Convert.ToInt32(drv["ReceiptID"]); MovingAverage movingAverage = new MovingAverage(); movingAverage.DataSource = MovingAverageHistory.GetMovingAverageByReceiptID(ReceiptID); movingAverage.ShowPreview(); } }