数据库管理软件是MS SQL，数据库是微软的NorthWind。

主体代码,完整的解决方案见最下方

1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Text; 5  6 namespace TestCodeFirst 7 { 8     class Program 9     {10         static void Main(string[] args)11         {12             ValidaProduct();13             UpdateProduct();14             GetSpecialProduct();15         }16 17         private static void ValidaProduct()18         {19             using (Northwind northwind = new Northwind())20             {21                 var product = northwind.Products.Find(1);22                 Console.WriteLine(string.Format("product.Name{0} product.UnitPrice:{1}", product.ProductName, product.UnitPrice));23                 product.ProductName = null;24                 product.UnitPrice = 2.33M;25                 product.Discontinued = false;26                 northwind.SaveChanges();27             }28         }29 30         private static void UpdateProduct()31         {32             using (Northwind northwind = new Northwind())33             {34                 var product = northwind.Products.Find(1);35                 Console.WriteLine(string.Format("product.Name{0} product.UnitPrice:{1}",product.ProductName, product.UnitPrice));36                 product.UnitPrice = 2.33M;37                 product.Discontinued = false;38                 northwind.SaveChanges();39 40                 var product2 = northwind.Products.Find(1);41                 Console.WriteLine(string.Format("product.Name{0} product.UnitPrice:{1}", product.ProductName, product2.UnitPrice));42             }43         }44 45         private static void GetSpecialProduct()46         {47             using (Northwind northwind = new Northwind())48             {49                 var product = from p in northwind.Products50                               where p.Category.CategoryName == "Beverages"51                               select p;52                 foreach (var item in product)53                 {54                     Console.WriteLine(string.Format("ProductName:{0}", item.ProductName));55                 }56                 Console.WriteLine(string.Format("执行结果：{0}", product == null));57             }58         }59     }60 }