Question

我是xaml和c＃的新手，如果ProductID已经存在，如何阻止我的按钮点击事件向Listview添加新行

private void btnAddToOrder_Click(object sender, RoutedEventArgs e)
{
    //addtoorders
    if (listStocks.SelectedIndex >= 0)
    {
        DataRowView row = (DataRowView)listStocks.SelectedItems[0];

        List<Orders> orders = new List<Orders>();
        orders.Add(new Orders()
        {
            ProductID = row["productID"].ToString(),
            ProductName = row["productName"].ToString(),
            Price = Convert.ToDouble(row["sellingPrice"]),
            Quantity = Convert.ToInt32(row["quantity"])

        });
        listOrders.Items.Add(orders);
      }
 }

Answer 1

首先为什么要创建Orders的新对象？

您可以使用需要

的LINQ

  using System.Linq;

然后使用

 var found = ordersobject.FirstOrDefault(x => x.Contains(row["productID"].ToString())); //Replace ordersobject with the Orders object that you have created

最后，如果var found返回null，则添加产品，即

private void btnAddToOrder_Click(object sender, RoutedEventArgs e)
{
    //addtoorders
    if (listStocks.SelectedIndex >= 0)
    {

    DataRowView row = (DataRowView)listStocks.SelectedItems[0];

    var found = ordersobject.FirstOrDefault(x=>x.Contains(row["productID"].ToString()));


        if(found == null)
        {
            //According to my knowledge a new object i.e., 
            //List<Orders> orders = new List<Orders>(); doesn't have to be defined below 
            //provided that you have defined an object of class Orders before, 
            //unless you want to create various objects of Orders. 
            //Which will cause a lot of trouble in future.
            List<Orders> orders = new List<Orders>();
            orders.Add(new Orders()
            {
                 ProductID = row["productID"].ToString(),
                 ProductName = row["productName"].ToString(),
                 Price = Convert.ToDouble(row["sellingPrice"]),
                 Quantity = Convert.ToInt32(row["quantity"])

            });
            listOrders.Items.Add(orders);
            }
        }
    }
 }

Answer 2

我认为本准则可以帮助您：

 private void btnAddToOrder_Click(object sender, RoutedEventArgs e)
 {
   //addtoorders
  if (listStocks.SelectedIndex >= 0)
  {
      DataRowView row = (DataRowView)listStocks.SelectedItems[0];
      Orders o=(Orders)row;
      List<Orders> orderlist=( List<Orders>)listOrders.ItemsSource;
      if(orderlist.Find(x=>x.PRoductID==c1.PRoductID)!=null)
        {
           MessageBox.Show("This Product already exists!");
        }
      else
       {
          listOrders.Items.Add(orders);
       }   

  }

}

Answer 3

private void btnAddToOrder_Click(object sender, RoutedEventArgs e)
    {


        //addtoorders
        if (listStocks.SelectedIndex >= 0)
        {
            DataRowView row = (DataRowView)listStocks.SelectedItems[0];

            Orders newOrder = new Orders()
            {
                ProductID = row["productID"].ToString(),
                ProductName = row["productName"].ToString(),
                Price = Convert.ToDouble(row["sellingPrice"]),
                Quantity = Convert.ToInt32(row["quantity"])

            };
            List<Orders> orders = new List<Orders>();
            //
            bool found = false;
            foreach(Orders order in orders)
            {
                if (order.Equals(newOrder))
                {
                    //if Found Order Equal NewOrder
                    found = true;
                    break;
                }
            }
            if(found == true)
            {
                Console.WriteLine("We are Found Order = NewOrder");
                return; //Exit From Method
            }
            //If Found == false
            orders.Add(newOrder);
            listOrders.Items.Add(orders);
        }
    }

阻止按钮单击事件，在条件下向Listview添加行

3 个答案: