Entity Framework 4.0 ObjectContext下的各种方法实践

1. AddObject

 1         private static void AddObjectDemo1()
 2         {
 3             Console.WriteLine("--------Begin AddObjectDemo1");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 Customers addCustomer = edm.Customers.FirstOrDefault(c => c.CustomerID == "001");
 7                 if (addCustomer == null)
 8                 {
 9                     Customers customer = new Customers { CustomerID = "001", CompanyName = "HongFan" };
10                     edm.AddObject("Customers", customer);
11                     int result = edm.SaveChanges();
12                 }
13                 Console.WriteLine("CustomerID={0}, CompanyName={1}", addCustomer.CustomerID, addCustomer.CompanyName);
14             }
15             Console.WriteLine("--------End AddObjectDemo1");
16         }

 

2. AddObject 带映射关系

 1         private static void AddObjectDemo2()
 2         {
 3             Console.WriteLine("--------Begin AddObjectDemo2");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 Categories cate1 = new Categories { CategoryName = "Category1" };
 7                 Categories cate2 = new Categories { CategoryName = "Category2" };
 8                 Products product1 = new Products { ProductName = "Category1--Product1", Discontinued = true };
 9                 Products product2 = new Products { ProductName = "Category2--Product2", Discontinued = false };
10 
11                 cate1.Products.Add(product1);
12                 cate2.Products.Add(product2);
13 
14                 edm.Categories.AddObject(cate1);
15                 edm.Categories.AddObject(cate2);
16 
17                 edm.SaveChanges();
18 
19                 Console.WriteLine("Linq2Entities...");
20 
21                 var categories = from category in edm.Categories
22                                  where category.CategoryName == "Category1" || category.CategoryName == "Category2"
23                                  select category;
24 
25                 foreach (var category in categories)
26                 {
27                     Console.WriteLine("分类：{0}", category.CategoryName);
28                     foreach (var product in category.Products)
29                     {
30                         Console.WriteLine("产品：{0}", product.ProductName);
31                     }
32                 }
33 
34                 Console.WriteLine("EntitySQL...");
35 
36                 var esql = @"select value c from Categories as c where c.CategoryName='Category2' or c.CategoryName='Category2'";
37                 var categoriesESQL = edm.CreateQuery<Categories>(esql);
38 
39                 foreach (var category in categories)
40                 {
41                     Console.WriteLine("分类：{0}", category.CategoryName);
42                     foreach (var product in category.Products)
43                     {
44                         Console.WriteLine("产品：{0}", product.ProductName);
45                     }
46                 }
47             }
48             Console.WriteLine("--------End AddObjectDemo2");
49         }

3. DeleteObject

 1         private static void DeleteObjectDemo()
 2         {
 3             Console.WriteLine("--------Begin DeleteObjectDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 Customers customer = edm.Customers.FirstOrDefault(c => c.CustomerID == "001");
 7                 if (customer != null)
 8                 {
 9                     edm.DeleteObject(customer);
10                     int result = edm.SaveChanges();
11                 }
12 
13                 customer = edm.Customers.FirstOrDefault(c => c.CustomerID == "001");
14                 if (customer == null)
15                 {
16                     Console.WriteLine("CustomerID为001的客户已被删除成功。");
17                 }
18                 else
19                 {
20                     Console.WriteLine("CustomerID={0}，CompanyName={1}", customer.CustomerID, customer.CompanyName);
21                 }
22             }
23             Console.WriteLine("--------End DeleteObjectDemo");
24         }

4. SaveChanges

 1         private static void SaveChangesDemo()
 2         {
 3             Console.WriteLine("--------Begin SaveChangesDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 Customers customer = edm.Customers.FirstOrDefault(c => c.CustomerID == "001");
 7                 if (customer != null)
 8                 {
 9                     customer.CompanyName = "HongFanKeJi";
10                     int result = edm.SaveChanges();
11                     Customers updateC = edm.Customers.FirstOrDefault(c => c.CustomerID == "001");
12                     Console.WriteLine("CustomerID={0}, CompanyName={1}", updateC.CustomerID, updateC.CompanyName);
13                 }
14             }
15             Console.WriteLine("--------End SaveChangesDemo");
16         }

5. ExecuteStoreCommand

 1         private static void ExecuteStoreCommandDemo()
 2         {
 3             Console.WriteLine("--------Begin ExecuteStoreCommandDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 string strSql = @"insert into Customers(CustomerID, CompanyName) values(@CustomerID, @CompanyName)";
 7                 var parm = new DbParameter[] {
 8                     new SqlParameter { ParameterName = "CustomerID", Value = "002" },
 9                     new SqlParameter { ParameterName = "CompanyName", Value = "GuangzhouHongFan" }
10                 };
11 
12                 Customers customer = edm.Customers.FirstOrDefault(c => c.CustomerID == "002");
13                 if (customer != null)
14                 {
15                     edm.Customers.DeleteObject(customer);
16                     edm.SaveChanges();
17                 }
18                 int rowCount = edm.ExecuteStoreCommand(strSql, parm);
19                 Console.WriteLine("{0} rows inserted", rowCount.ToString());
20 
21                 Customers customerInserted = edm.Customers.FirstOrDefault(c => c.CustomerID == "002");
22                 Console.WriteLine("CustomerID={0}, CompanyName={1}", customerInserted.CustomerID, customerInserted.CompanyName);
23             }
24             Console.WriteLine("--------End ExecuteStoreCommandDemo");
25         }

6.ExecuteStoreQuery

 1         private static void ExecuteStoreQueryDemo()
 2         {
 3             Console.WriteLine("--------Begin ExecuteStoreQueryDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 string strSql = "select * from Customers where CompanyName=@CompanyName";
 7                 var parm = new DbParameter[] {
 8                     new SqlParameter { ParameterName = "CompanyName", Value = "GuangzhouHongfan"}
 9                 };
10                 var customers = edm.ExecuteStoreQuery<Customers>(strSql, parm);
11 
12                 foreach (var customer in customers)
13                 {
14                     Console.WriteLine("CustomerID={0}, CompanyName={1}", customer.CustomerID, customer.CompanyName);
15                 }
16             }
17             Console.WriteLine("--------End ExecuteStoreQueryDemo");
18         }

7. Execute

 1         private static void ExecuteDemo()
 2         {
 3             Console.WriteLine("--------Begin ExecuteDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 string strSql = "select value c from NorthwindEntities.Customers as c order by c.CustomerID limit 10";
 7 
 8                 ObjectQuery<Customers> query = edm.CreateQuery<Customers>(strSql);
 9                 ObjectResult<Customers> results = query.Execute(MergeOption.NoTracking);
10                 foreach (Customers c in query)
11                 {
12                     Console.WriteLine("CustomerID={0}, CompanyName={1}", c.CustomerID, c.CompanyName);
13                 }
14 
15                 Console.WriteLine(Environment.NewLine);
16 
17                 foreach (Customers c in results)
18                 {
19                     Console.WriteLine("CustomerID={0}, CompanyName={1}", c.CustomerID, c.CompanyName);
20                 }
21             }
22             Console.WriteLine("--------End ExecuteDemo");
23         }

8. ToTraceString

 1         private static void ToTraceStringDemo()
 2         {
 3             Console.WriteLine("--------Begin ToTraceStringDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 string strSql = "select value c from NorthwindEntities.Customers as c order by c.CustomerID limit 10";
 7 
 8                 ObjectQuery<Customers> query = edm.CreateQuery<Customers>(strSql);
 9                 Console.WriteLine("The sql for this statement: select value c from NorthwindEntities.Customers as c order by c.CustomerID limit 10\r\n");
10                 Console.WriteLine(query.ToTraceString());
11             }
12             Console.WriteLine("--------End ToTraceStringDemo");
13         }

9. Where

 1         private static void WhereDemo()
 2         {
 3             Console.WriteLine("--------Begin WhereDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 string strSql = "select value c from NorthwindEntities.Customers as c order by c.CustomerID limit 10";
 7 
 8                 ObjectQuery<Customers> query = edm.CreateQuery<Customers>(strSql);
 9                 query.Name = "a";
10                 query = query.Where("a.CustomerID=@customerID", new ObjectParameter("customerID", "001"));
11 
12                 foreach (Customers c in query)
13                 {
14                     Console.WriteLine("CustomerID={0}, CompanyName={1}", c.CustomerID, c.CompanyName);
15                 }
16             }
17             Console.WriteLine("--------End WhereDemo");
18         }

10. FirstOrDefault

 1         private static void FirstOrDefaultDemo()
 2         {
 3             Console.WriteLine("--------Begin FirstOrDefaultDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 string strSql = "select value c from NorthwindEntities.Customers as c order by c.CustomerID limit 10";
 7 
 8                 ObjectQuery<Customers> query = edm.CreateQuery<Customers>(strSql);
 9                 
10                 //如果没有符合条件的数据，那么将会抛出异常。
11                 Customers c1 = query.First();
12 
13                 //如果没有符合条件的数据，那么将返回null。
14                 Customers c2 = query.FirstOrDefault();
15 
16                 Console.WriteLine("CustomerID={0}, CompanyName={1}", c1.CustomerID, c1.CompanyName);
17                 Console.WriteLine("CustomerID={0}, CompanyName={1}", c2.CustomerID, c2.CompanyName);
18             }
19             Console.WriteLine("--------End FirstOrDefaultDemo");
20         }

11. Distinct

 1         private static void DistinctDemo()
 2         {
 3             Console.WriteLine("--------Begin DistinctDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 string strSql = "select value c.City from NorthwindEntities.Customers as c order by c.CustomerID limit 10";
 7 
 8                 ObjectQuery<string> query = edm.CreateQuery<string>(strSql);
 9                 query = query.Distinct();
10 
11                 foreach (string city in query)
12                 {
13                     Console.WriteLine("City：{0}", city);
14                 }
15             }
16             Console.WriteLine("--------End DistinctDemo");
17         }

12. Include

 1         private static void IncludeDemo()
 2         {
 3             Console.WriteLine("--------Begin IncludeDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 string strSql = "select value c from NorthwindEntities.Customers as c where c.CustomerID='001'";
 7 
 8                 ObjectQuery<Customers> query = edm.CreateQuery<Customers>(strSql);
 9                 query = query.Include("Orders");
10 
11                 foreach (Customers customer in query)
12                 {
13                     Console.WriteLine("CustomerID={0}, OrderCount={1}", customer.CustomerID, customer.Orders.Count);
14                 }
15 
16                 Console.WriteLine(query.ToTraceString());
17             }
18             Console.WriteLine("--------End IncludeDemo");
19         }

13. OrderBy

 1         private static void OrderByDemo()
 2         {
 3             Console.WriteLine("--------Begin OrderByDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 string strSql = "select value c from NorthwindEntities.Customers as c order by c.CustomerID limit 10";
 7 
 8                 ObjectQuery<Customers> query = edm.CreateQuery<Customers>(strSql);
 9                 query.OrderBy("it.country asc, it.city asc");
10 
11                 // 也可以这样写
12                 //query.OrderBy("it.country asc");
13                 //query.OrderBy("it.city asc");
14 
15                 foreach (Customers c in query)
16                 {
17                     Console.WriteLine("CustomerID={0}, CompanyName={1}", c.CustomerID, c.CompanyName);
18                 }
19             }
20             Console.WriteLine("--------End OrderByDemo");
21         }

14. Select

 1         private static void SelectDemo()
 2         {
 3             Console.WriteLine("--------Begin SelectDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 string strSql = "select value c from NorthwindEntities.Customers as c order by c.CustomerID limit 10";
 7 
 8                 ObjectQuery<Customers> query = edm.CreateQuery<Customers>(strSql);
 9                 ObjectQuery<DbDataRecord> records = query.Select("it.customerid, it.country");
10 
11                 foreach (DbDataRecord c in records)
12                 {
13                     Console.WriteLine("CustomerID={0}, Country={1}", c["customerid"], c["country"]);
14                 }
15                 Console.WriteLine(records.ToTraceString());
16             }
17             Console.WriteLine("--------End SelectDemo");
18         }

15. SelectValue

 1         private static void SelectValueDemo()
 2         {
 3             Console.WriteLine("--------Begin SelectValueDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 string strSql = "select value c from NorthwindEntities.Customers as c order by c.CustomerID limit 10";
 7 
 8                 ObjectQuery<Customers> query = edm.CreateQuery<Customers>(strSql);
 9                 ObjectQuery<string> records = query.SelectValue<string>("it.customerid");
10 
11                 foreach (string c in records)
12                 {
13                     Console.WriteLine("CustomerID={0}", c);
14                 }
15                 Console.WriteLine(records.ToTraceString());
16             }
17             Console.WriteLine("--------End SelectValueDemo");
18         }

16. Skip、Top

 1         private static void SkipTopDemo()
 2         {
 3             Console.WriteLine("--------Begin SkipTopDemo");
 4             using (var edm = new NorthwindEntities())
 5             {
 6                 string strSql = "select value c from NorthwindEntities.Customers as c order by c.CustomerID";
 7 
 8                 ObjectQuery<Customers> query = edm.CreateQuery<Customers>(strSql);
 9                 query = query.Skip("it.customerid asc", "10"); // 排序，跳过条数
10                 query = query.Top("10");
11 
12                 foreach (Customers c in query)
13                 {
14                     Console.WriteLine("CustomerID={0}", c.CustomerID);
15                 }
16                 Console.WriteLine(query.ToTraceString());
17             }
18             Console.WriteLine("--------End SkipTopDemo");
19         }