如何添加列表<B>到对象A，其中List&lt;B&gt;是 A 类的一部分 [英] How to add List&lt;B&gt; to Object A, where List&lt;B&gt; is part of class A

问题描述

我有两类客户和产品，如下所示.我正在从数据库获取数据并将其读入 SqlDataReader.从那我必须将它读到客户对象.我们将为每个客户提供多种产品.在这里，我必须将 Product 对象添加到 Customer Object(我们可能为每个客户提供多个产品.请提供任何建议......这样做的最佳方法是什么?

I have two classes of Customer and Products like below. I am getting data from DataBase and reading it into SqlDataReader. From that I have to read it to Customer Object. we will have multiple Products for each Customer. Here I have to add Product object to Customer Object(we may have multiple products for each customer. Any suggestions please.. what is the best way to do this?

public class Customer
{
    public int CustomerId {get;set;}
    public string Name {get;set;}
    public List<Products> _products {get;set;}      
}

public class Products
{
    public int CustomerId {get;set;}
    public int ProductId {get;set;}
    public string Name {get;set;}
    public int Quantity {get;set;} 
}


While(dataReader.Read())
{
    var _customer = new Customer{
        CustomerId = (int)rdr["CustomerId"];
        Name = (string)rdr["CustomerName"];
        City    = (string)rdr["City"];
    };

    var _product = new Products
    {
        CustomerId = (int)rdr["CustomerId"];
        ProductId = (int)rdr["ProductId"];
        Name = (string)rdr["ProductName"];
        Quantity = (int)["Quantity"];
    };
}

推荐答案

public List<Customer> GetCustomers(SqlConnection conn) {
  using (conn);
  conn.Open();
  SqlCommand command = new SqlCommand("your_query;",conn);
  // your query must return in order
  // customerId, customerName, city, productId, productName, quantity
  SqlDataReader reader = command.ExecuteReader();

  var customers = new List<Customer>();
  var products = new List<Product>();

  while (reader.Read()) {  
    var customerId = reader.GetInt32(0);
    var customer = new Customer() {
      CustomerId = customerId,
      Name = reader.GetString(1),
      City    = reader.GetString(2)
    };

    var existing = customers.Where(x => x.CustomerId == customerId).FirstOrDefault();
    if (existing == null) {
       customers.Add(customer);
    }

    var product = new Products
    {
      CustomerId = customerId,
      ProductId = reader.GetInt32(3),
      Name = reader.GetString(4),
      Quantity = reader.GetInt32(5)
    };
    products.Add(product);
  }
  reader.Close();

  return customers.ForEach(item => {
     item.Products = products.Where(x => x.customerId == item.CustomerId).ToList();
    });
  }
}

如何使用数据读取器

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