Entity Framework 4.0 ObjectContext下的各种方法实践

View Code

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         }

View Code

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         }

View Code

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         }

View Code

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         }

View Code

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         }

View Code

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         }

View Code

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         }

View Code

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         }

View Code

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         }

View Code

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         }

View Code

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         }

View Code

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         }

View Code

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         }

View Code

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         }

View Code

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         }

View Code

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         }

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Entity Framework 4.0 ObjectContext下的各种方法实践

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