ADO.NET中的多数据表操作之读取

Select orderID,OrderDate,CustomerID FROM orders Where CustomerID IN

(Select CustomerID FROM Customers Where CustomerID LIKE 'A%')

Select orderID,ProductID,UnitPrice,Quantity,Discount FROM [Order Details] Where orderID IN

(Select orderID FROM orders Where CustomerID IN

(Select CustomerID FROM Customers Where CustomerID LIKE 'A%'))

GO

为了减少数据量，这里只取了CustomerID以’A’开头的数据。建立DataAccess类来管理窗体同数据层的交互：

using System;

using System.Data;

using System.Data.SqlClient;

using Microsoft.ApplicationBlocks.Data;

namespace WinformTest

{

public class DataAccess

{

private string _connstring = "data source=(local);initial catalog=Northwind;uid=csharp;pwd=c#.net2004;";

private SqlConnection _conn;

///构造函数

public DataAccess()

{

_conn = new SqlConnection(_connstring);