1、使用ADO.NET來連接SQL Server數據庫
創建一個SqlConnection對象，在它的ConnectionString屬性中指定要使用的數據庫，然后調用它的Open方法
1SqlConnection dataConnection = new SqlConnection();
2            string userID = "sa";
3            string password = "test";
4            try
5            {
6                dataConnection.ConnectionString = String.Format("User ID={0};Password={1};Persist Security Info=True;Initial Catalog=Northwind;Data Source=TXC-NOTEBOOK", userID, password);
7                dataConnection.Open();

2、使用ADO.NET來創建并執行查詢
創建一個SqlCommand對象，將它的Connection屬性設為一個有效的SqlConnection對象，將它的CommandText設為一個有效的SQL SELECT語句。調用ExecuteReader方法來運行查詢并創建一個SqlDataReader對象
 1Console.Write("please enter a customer ID(5 characters):");
 2                string customerId = Console.ReadLine();
 3
 4                SqlCommand dataCommand = new SqlCommand();
 5                dataCommand.Connection = dataConnection;
 6                dataCommand.CommandText = "select OrderID,OrderDate,ShippedDate,ShipName,ShipAddress,ShipCity,ShipCountry " +
 7                    "from Orders where CustomerID='" + customerId + "'";
 8                Console.WriteLine("About to execute:{0}\n\n", dataCommand.CommandText);
 9
10                SqlDataReader dataReader = dataCommand.ExecuteReader();

3、使用ADO.NET的SqlDataReader對象來獲取數據
使用IsDBNull方法確保數據不是null。如果數據不是null,就用恰當的GetXXX方法（例如GetString和GetInt32等）來獲取數據
 1while (dataReader.Read())
 2                {
 3                    int orderId = dataReader.GetInt32(0);
 4                    if (dataReader.IsDBNull(2))
 5                    {
 6                        Console.WriteLine("Order {0} not yet shipped\n\n", orderId);
 7                    }
 8                    else
 9                    {
10
11                        DateTime orderDate = dataReader.GetDateTime(1);
12                        DateTime shipDate = dataReader.GetDateTime(2);
13                        string shipName = dataReader.GetString(3);
14                        string shipAddress = dataReader.GetString(4);
15                        string shipCity = dataReader.GetString(5);
16                        string shipCountry = dataReader.GetString(6);
17
18                        Console.WriteLine("order:{0}\nPlaced:{1}\nShipped:{2}\n" +
19                            "To Address:{3}\n{4}\n{5}\n{6}\n\n", orderId, orderDate, shipDate, shipName, shipAddress, shipCity, shipCountry);
20
21                    }
22
23                }
24                dataReader.Close();

4、定義實體類
定義一個類，在類中為每個列都定義一個public property。在類定義的前一行，附加一個Table attribute。在Table attribute中，指定底層數據庫中的表名。在每個public property定義的前一行，都附加一個Column attribute。在Column attribute中，用參數來指定數據庫中對應的列的名稱、類型以及是否允許為空
 1    [Table(Name="Orders")]
 2   public  class Order
 3    {
 4        [Column(IsPrimaryKey=true,CanBeNull=false)]
 5        public int OrderID { get; set; }
 6
 7        [Column]
 8        public string CustomerID { get; set; }
 9
10        [Column]
11        public DateTime? OrderDate { get; set; }
12
13        [Column]
14        public DateTime? ShippedDate { get; set; }
15
16        [Column]
17        public string ShipName { get; set; }
18
19        [Column]
20        public string ShipAddress { get; set; }
21
22        [Column]
23        public string ShipCity { get; set; }
24
25        [Column]
26        public string ShipCountry { get; set; }
27    }

5、使用DLINQ創建并執行查詢
創建一個新的DataContext變量，指定一個連接字符串來連接數據庫。創建一個Table集合變量，它所基于的實體類必須和你要查詢的表對應。定義一個DLINQ查詢，它標識要從數據庫中獲取的數據，并返回實體的一個可枚舉的集合。遍歷可枚舉的集合，即可獲取每一行的數據，并對結果進行處理。
 1using System;
 2using System.Collections.Generic;
 3using System.Linq;
 4using System.Text;
 5using System.Data.Linq;
 6using DLINQOrders.model;
 7
 8namespace DLINQOrders.dao
 9{
10    public class Northwind:DataContext
11    {
12        public Table<Order> Orders;
13        public Northwind(string connectionInfo)
14            : base(connectionInfo)
15        {
16
17        }
18    }
19}
20


 1using System;
 2using System.Collections.Generic;
 3using System.Linq;
 4using System.Text;
 5
 6using System.Data.Linq;
 7using System.Data.Linq.Mapping;
 8using System.Data.SqlClient;
 9
10namespace DLINQOrders.model
11{
12    [Table(Name="Orders")]
13   public  class Order
14    {
15        [Column(IsPrimaryKey=true,CanBeNull=false)]
16        public int OrderID { get; set; }
17
18        [Column]
19        public string CustomerID { get; set; }
20
21        [Column]
22        public DateTime? OrderDate { get; set; }
23
24        [Column]
25        public DateTime? ShippedDate { get; set; }
26
27        [Column]
28        public string ShipName { get; set; }
29
30        [Column]
31        public string ShipAddress { get; set; }
32
33        [Column]
34        public string ShipCity { get; set; }
35
36        [Column]
37        public string ShipCountry { get; set; }
38    }
39}
40


 1using System;
 2using System.Collections.Generic;
 3using System.Linq;
 4using System.Text;
 5using DLINQOrders.dao;
 6using System.Data.SqlClient;
 7
 8namespace DLINQOrders
 9{
10    class DLINQReport
11    {
12        static void Main(string[] args)
13        {
14            Northwind northwindDB = new Northwind("Data Source=TXC-NOTEBOOK;Initial Catalog=Northwind;Persist Security Info=True;User ID=sa;Password=test");
15            try
16            {
17                Console.WriteLine("Please enter a customer ID(5 characters):");
18                string customerId = Console.ReadLine();
19
20                var ordersQuery = from o in northwindDB.Orders
21                                  where String.Equals(o.CustomerID, customerId)
22                                  select o;
23                foreach (var order in ordersQuery)
24                {
25                    if (order.ShippedDate == null)
26                    {
27                        Console.WriteLine("Order {0} not yet shipped\n\n", order.OrderID);
28                    }
29                    else
30                    {
31                        Console.WriteLine("Order:{0}\nPlaced:{1}\nShipped:{2}\n" +
32                            "To Address:{3}\n{4}\n{5}\n{6}\n\n", order.OrderID,
33                            order.OrderDate, order.ShippedDate, order.ShipName, order.ShipAddress, order.ShipCity,
34                            order.ShipCountry);
35                    }
36
37                }
38            }
39            catch (SqlException e)
40            {
41                Console.WriteLine("Error accessing the database:{0}", e.Message);
42            }
43        }
44    }
45}
46