private void PurchaseProductComboBox_SelectedIndexChanged(object sender, EventArgs e) { ModelPurchase _modelPurchase = new ModelPurchase(); _modelPurchase.purchaseProduct = purchaseProductComboBox.Text; PurchaseManager _purchaseManager = new PurchaseManager(); availableQtyTextBox.Text = _purchaseManager.AvaiablePurchaseQuantity(_modelPurchase); totalMrpTextBox.Text = _purchaseManager.TotalMrp(_modelPurchase); }