將C#物件序列化為包含串列的JSON

我要做的是從我的資料庫中獲取一些資料（客戶訂購了他訂購的所有物品）將其轉換為包含所述物品串列的 JSON，以便我可以通過 POST 請求發送它。我想創建一個 JSON 物件，其中包含客戶訂單的詳細資訊以及該訂單中包含的產品串列。這就是我希望我的 JSON 的樣子：

{
  "account_code": "00000",       
  "advance_payment": false,       
  "date": [today's date],
  "order_items": 
   [
     {
       "item_id": 0, 
       "product_Price ": "105.00",  
       "order_Item_Rebate: "",     
       "product_code": "000001",   
       "quantity": 1
     },
     {
       "item_id": 1, 
       "product_Price ": "55.00",  
       "price": "",     
       "product_code": "000002",   
       "quantity": 5
     },
     {
       "item_id": 2, 
       "product_Price ": "15.00",  
       "price": "",     
       "product_code": "000003",   
       "quantity": 3
     }
   ]
}

但我得到的是：

{
  "account_code": "00000",       
  "advance_payment": false,       
  "date": [today's date],
  "order_items": 
   [
     {
       "item_id": 0, 
       "roduct_Price ": "105.00",  
       "order_Item_Rebate: "",     
       "product_code": "000001",   
       "quantity": 1
     }
   ]
},
{
  "account_code": "00000",       
  "advance_payment": false,       
  "date": [today's date],
  "order_items": 
   [
     {
       "item_id": 1, 
       "roduct_Price ": "55.00",  
       "price": "",     
       "product_code": "000002",   
       "quantity": 5
     }
   ]
},
{
  "account_code": "00000",       
  "advance_payment": false,       
  "date": [today's date],
  "order_items": 
   [
     {
       "item_id": 2, 
       "product_Price ": "15.00",  
       "price": "",     
       "product_code": "000003",   
       "quantity": 3
     }
   ]
}

我為同一個客戶（account_code）獲得了多個 JSON 物件，而不是一個帶有專案串列的 JSON 物件。

I'm getting this data from database using ADO.NET and I read this data with SqlDataReader. Inside SqlDataReader I created a new object and filled it with details about my order. It all works, but problem is order_items which should be a list of all items from the order. I want one order with multiple items in it, not a different order for every item. Using code below I am able to get data from my database, but I don't know how to group order_items with the order they should be in.

List<OrderModel> orderList = new List<OrderModel>();
using (SqlDataReader rdr = await cmd.ExecuteReaderAsync())
                    {
                        while (rdr.Read())
                        {
                            OrderModel order = new OrderModel()
                            {
                                Account_code = rdr[0].ToString(),
                                Advance_payment = false,
                                Date = DateTime.Now.Date,
                                Order_Items = new List<Order_items>()
                                    {
                                     //Here is where I should do something instead of creating new
                                     //Order_items, but I don't know what
                                        new Order_items()
                                        {
                                            Order_Item_Rebate = rdr[1].ToString(),
                                            Product_Price = rdr[2].ToString(),
                                            Product_Code = rdr[3].ToString(),
                                            Quantity = rdr[4].ToString()
                                        }
                                    }

                            };
                            orderList.Add(order);
                        }
                        var jsonString = JsonConvert.SerializeObject(orderList);
                        return jsonString;
                    }

My OrderModel class looks like this:

public class OrderModel
    {
        public string Account_code { get; set; } 
        public bool Advance_payment { get; set; } 
        public DateTime Date { get; set; }
        public List<Order_items> Order_Items { get; set; } 
    }

    public class Order_items
    {
        public string Order_Item_Rebate { get; set; } 
        public string Product_Price { get; set; } 
        public string Product_Code { get; set; }
        public string Quantity { get; set; }
    }
  

And table from my database looks like this:

我看到過類似的問題，人們建議使用一系列字典，但我不確定我是否理解它們將如何提供幫助。我是新手，所以如果問題不是很聰明，我很抱歉。

uj5u.com熱心網友回復：

SQL查詢會產生“扁平化”的資料，所以需要自己分組。沿著這條線的東西：

var orderDict = new Dictionary<string, OrderModel>(); // mapping from account code to order object
while (rdr.Read())
{
   var accCode = rdr[0].ToString();
   
   // if no object previously added - add a new one 
   if(!orderDict.TryGetValue(accCode, out var order))
   {
       order = new OrderModel()
       {
           Account_code = accCode ,
           Advance_payment = false,
           Date = DateTime.Now.Date,
           Order_Items = new List<Order_items>()
       };
       orderDict[accCode] = order;
   }

   // add details from current result line to order 
   order.Order_Items.Add(new Order_items() {...});
}

var jsonString = JsonConvert.SerializeObject(orderDict.Values); // serialize only values, not the whole dictionary

uj5u.com熱心網友回復：

所以，問題是你在回圈OrderModel的每次迭代中都創建了一個新的while (rdr.Read())。解決此問題的最直接方法是簡單地檢查基于 的現有in OrderModel，并僅在找不到時創建一個新實體。例如...orderListAccount_codeOrderModel

List<OrderModel> orderList = new List<OrderModel>();
using (SqlDataReader rdr = await cmd.ExecuteReaderAsync())
{
    while (rdr.Read())
    {
        // Check to see if there is already an instance of OrderModel with the
        // account code in the list.
        OrderModel order = orderList.FirstOrDefault(om => om.Account_code == rdr[0].ToString());
        if (order == null)
        {
            // If there isn't create a new instance of OrderModel and add it to
            // the list.
            order = new OrderModel
            {
                Account_code = rdr[0].ToString(),
                Advance_payment = false,
                Date = DateTime.Now.Date,
                Order_Items = new List<Order_items>()
            };
            orderList.Add(order);
        }
        
        // Now, just add the new item to Order_Items.
        order.Order_Items.Add(new Order_item
        {
            Order_Item_Rebate = rdr[1].ToString(),
            Product_Price = rdr[2].ToString(),
            Product_Code = rdr[3].ToString(),
            Quantity = rdr[4].ToString()
        });
    }
    var jsonString = JsonConvert.SerializeObject(orderList);
    return jsonString;
}

性能可能會很差，尤其是在orderList變大時，因為orderList每次回圈迭代都會迭代一次while。但是，這種基本方法應該有效。您需要確保只在結果集中創建一個，而不是OrderModel在回圈的每次迭代中創建一個。whileAccount_code

如果您可以控制查詢本身，則可以對結果進行排序Account_code以解決性能問題。

List<OrderModel> orderList = new List<OrderModel>();
using (SqlDataReader rdr = await cmd.ExecuteReaderAsync())
{
    OrderModel order = null;
    while (rdr.Read())
    {
        if (order == null || order.Account_code != rdr[0].ToString())
        {
            // The order is null, meaning that this is the first order model to be processed.
            // Or, the order's account code is different than the current account code on the result set, meaning we have begun processing a new order.
            // In either case, you need to add a new order to the list so
            // you can start filling in its items.
            order = new OrderModel
            {
                Account_code = rdr[0].ToString(),
                Advance_payment = false,
                Date = DateTime.Now.Date,
                Order_Items = new List<Order_items>()
            };
            orderList.Add(order);
        }        
        
        // Now, just add the new item to Order_Items.
        order.Order_Items.Add(new Order_item
        {
            Order_Item_Rebate = rdr[1].ToString(),
            Product_Price = rdr[2].ToString(),
            Product_Code = rdr[3].ToString(),
            Quantity = rdr[4].ToString()
        });
    }
    var jsonString = JsonConvert.SerializeObject(orderList);
    return jsonString;
}

僅當您可以按帳戶代碼對查詢結果進行排序時，上述方法才有效。

uj5u.com熱心網友回復：

1. 在回圈外定義order變數。while

var order = new OrderModel()
{
    Account_code = rdr[0].ToString(),
    Advance_payment = false,
    Date = DateTime.Now.Date,
    Order_Items = new List<Order_items>()
};        

2. 決議while回圈內的訂單項

using (SqlDataReader rdr = await cmd.ExecuteReaderAsync())
{
    while (rdr.Read())
    {
        var item = new Order_items()
        {
            Order_Item_Rebate = rdr[1].ToString(),
            Product_Price = rdr[2].ToString(),
            Product_Code = rdr[3].ToString(),
            Quantity = rdr[4].ToString()
        };
        order.Order_Items.Add(item);
    }
}

3. 僅OrderModel在回圈之后序列化

var jsonString = JsonConvert.SerializeObject(order);
return jsonString;

標籤：C＃ 数据库 ado.net

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