Entity Framework细节追踪

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为了加深对EF特性的了解，so，写了一些测试代码。测试结果也许对实际项目没什么用处，但是对理解EF的相关机制还是有一定帮助的。本文可能会不定期更新（加入新的测试用例=。=）。

一、事务

---

直接看代码。

1、所有SaveChange包裹在一个TransactionScope里面。

 1 [TestMethod]
 2 public void TestMethod1()
 3 {
 4     using (var entities = new SysProcessEntities())
 5     {
 6         using (TransactionScope scope = new TransactionScope())
 7         {
 8             try
 9             {
10                 var test = entities.SysUser.Where(o => o.OrganizationID == 1).ToList();
11                 var test2 = entities.SysRole.ToList();
12
13                 test[0].Code = "admin1";
14                 test2[0].Name = "dddd";
15                 entities.SaveChanges();
16
17                 test[0].Code = "admin";
18                 test2[0].Name = "全功能";
19                 entities.SaveChanges();
20
21                 scope.Complete();
22             }
23             catch (Exception e)
24             {
25
26             }
27         }
28     }
29 }

结果：

2、在1的基础上去掉TransactionScope

 1 [TestMethod]
 2 public void TestMethod1()
 3 {
 4     using (var entities = new SysProcessEntities())
 5     {
 6         var test = entities.SysUser.Where(o => o.OrganizationID == 1).ToList();
 7         var test2 = entities.SysRole.ToList();
 8
 9         test[0].Code = "admin1";
10         test2[0].Name = "dddd";
11         entities.SaveChanges();
12
13         test[0].Code = "admin";
14         test2[0].Name = "全功能";
15         entities.SaveChanges();
16     }
17 }

结果：

3、注释掉2的第9行和第13行，检查单独的一条语句是否自带事务。

 1 [TestMethod]
 2 public void TestMethod1()
 3 {
 4     using (var entities = new SysProcessEntities())
 5     {
 6         var test = entities.SysUser.Where(o => o.OrganizationID == 1).ToList();
 7         var test2 = entities.SysRole.ToList();
 8
 9         //test[0].Code = "admin1";
10         test2[0].Name = "dddd";
11         entities.SaveChanges();
12
13         //test[0].Code = "admin";
14         test2[0].Name = "全功能";
15         entities.SaveChanges();
16     }
17 }

结果：

4、直接写Sql-"update [SysProcess].[dbo].[SysRole] set [name]='全功能' where ID=1"，在查询分析器中执行，结果：

5、将1改为跨数据库

 1 [TestMethod]
 2 public void TestMethod1()
 3 {
 4     using (TransactionScope scope = new TransactionScope())
 5     {
 6         try
 7         {
 8             using (var entities = new SysProcessEntities())
 9             {
10                 var test = entities.SysUser.Where(o => o.OrganizationID == 1).ToList();
11                 var test2 = entities.SysRole.ToList();
12
13                 test[0].Code = "admin1";
14                 test2[0].Name = "dddd";
15                 entities.SaveChanges();
16
17                 test[0].Code = "admin";
18                 test2[0].Name = "全功能";
19                 entities.SaveChanges();
20             }
21             using (var entities = new DistributionEntities())
22             {
23                 var test = entities.VIPCard.ToList();
24                 test[0].Sex = true;
25                 entities.SaveChanges();
26             }
27
28             scope.Complete();
29         }
30         catch (Exception e)
31         {
32             string msg = e.Message;
33         }
34     }
35 }

结果：

于是整个世界美好了……

二、AsNoTracking

---

注意AsNoTracking要写在最终返回数据的那行代码中才有用，看代码：

 [TestMethod]
 public void TestMethod9()
 {
     using (var entities = new SysProcessEntities())
     {
         var ubs = entities.UserBrand.AsNoTracking();
         ).AsNoTracking();
         var brands = from ub in ubs
                         from ob in obs
                         where ub.BrandID == ob.BrandID
                         select ub.BrandID;
         var test = entities.ProBrand.Where(b => brands.Contains(b.ID)).ToList();
         Assert.AreEqual(EntityState.Detached, entities.Entry(test[]).State);
     }
 }

结果：

so，using之中应该这么写：

var ubs = entities.UserBrand;
);
var brands = from ub in ubs
                from ob in obs
                where ub.BrandID == ob.BrandID
                select ub.BrandID;
var test = entities.ProBrand.Where(b => brands.Contains(b.ID)).AsNoTracking().ToList();
Assert.AreEqual(EntityState.Detached, entities.Entry(test[]).State);

三、DbSet.Local

---

继续看代码：

1、

 public void TestMethod10()
 {
     var entities = new SysProcessEntities();
     var t1 = entities.ProBoduan.ToList();
     var t2 = entities.ProBoduan.ToList();
     Assert.AreEqual(t1[],t2[]);
 }

大家以为t1[0]是否等于t2[0]？答案是true。可是作为引用类型，我并没有重载它的Equals方法，照理应该为false才对呀。修改下测试代码：

 public void TestMethod10()
 {
     var entities = new SysProcessEntities();
     var t1 = entities.ProBoduan.ToList();
     var t2 = entities.ProBoduan.ToList();
     ].Name;
     t1[].Name = "随便取个名用来测试";
     Assert.AreEqual(name, t2[].Name);
 }

结果：。可知，t1[0]和t2[0]指向的是同一个对象，即t1和t2指向同一个数组地址，也就是entities.ProBoduan.Local指向的地址。不过数据库中，仍执行了两次取数操作。

2、then，加入AsNoTracking试试看：

public void TestMethod10()
{
    var entities = new SysProcessEntities();
    var t1 = entities.ProBoduan.AsNoTracking().ToList();
    var t2 = entities.ProBoduan.AsNoTracking().ToList();
    ].Name;
    t1[].Name = "随便取个名用来测试";
    Assert.AreEqual(name, t2[].Name); //true,t1的更改不影响t2，表明t1和t2指向不同地址
}

此时entities.ProBoduan.Local.Count为0。

3、

 public void TestMethod10()
 {
     var entities = new SysProcessEntities();
     var t2 = entities.ProBoduan.FirstOrDefault();

     var t1 = entities.ProBoduan.ToList();

 }

将第4行和第6行换下位置。

 public void TestMethod10()
 {
     var entities = new SysProcessEntities();
     var t1 = entities.ProBoduan.ToList();
     var count1 = entities.ProBoduan.Local.Count;//3
     var t2 = entities.ProBoduan.FirstOrDefault();

 }

四、AutoDetectChangesEnabled & ValidateOnSaveEnabled

---

 public void TestMethod9()
 {
     using (var entities = new SysProcessEntities())
     {
         entities.Configuration.AutoDetectChangesEnabled = false;
         var ubs = entities.UserBrand;
         );
         var brands = from ub in ubs
                         from ob in obs
                         where ub.BrandID == ob.BrandID
                         select ub.BrandID;
         var test = entities.ProBrand.Where(b => brands.Contains(b.ID)).ToList();
         ]).State;
         test[].Description = "ggggg";
         ]).State;
         entities.ProBrand.Remove(test[]);
     }
 }

t1、t2皆为EntityState.Unchanged，原因是entities.Configuration.AutoDetectChangesEnabled = false;若设为true，那么t2将为EntityState.Modified。注意此项设置对Added和Deleted没影响。当我们循环Add大批量数据到上下文中时，设为false将对性能有非常大的提升;该属性设置对循环修改已跟踪实体的属性(entity.Property = XXXX)关系不大，大批量修改已跟踪实体的属性的效率我测试过，非常快（不管是true还是false；当然设为false，然后修改实体属性，没什么意义）。

猜测：ValidateOnSaveEnabled表示在SaveChanges()时是否根据映射文件等判断实体是否符合规则（如Key是否被改变，默认已跟踪实体是不能手动改变Key值的等），以后测试！

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