entity-framework - EF Core-在保存之前设置时间戳仍然使用旧值

Question

我有一个带有时间戳(并发 token )列的模型。我正在尝试编写一个集成测试，在其中检查它是否按预期工作，但没有成功。我的测试如下

获取应通过HttpClient调用从Web api更新的实体。

直接向上下文发出请求，并获得相同的实体

从步骤2开始更改实体的属性。

保存在步骤3中更新的实体。

从步骤1更改实体的属性。

将带有HttpClient的新实体的放置请求发送到Web Api。

在我的Web API中，我首先从数据库中获取实体，并从我从客户端获得的实体和时间戳值中进行设置。现在，我在api Controller 中的实体对象具有与数据库中不同的Timestamp值。现在，我希望savechanges会失败，但是不会。而是将实体保存到数据库并生成新的时间戳值。我使用Sql Server Profiler进行了检查，以查看生成的查询，结果发现该查询仍在使用旧的Timestamp值，而不是我在api Controller 中分配给实体的值。

这是什么原因呢？与Timestamp是数据库生成的值有关，它使EF忽略了业务层对其所做的更改是否与之相关？

完整的测试应用程序可以在这里找到: https://github.com/Abrissirba/EfTimestampBug

    public class BaseModel
    {
        [Timestamp]
        public byte[] Timestamp { get; set; }
    }

    public class Person : BaseModel
    {
        public int Id { get; set; }

        public String Title { get; set; }
    }

    public class Context : DbContext
    {
        public Context()
        {}

        public Context(DbContextOptions options) : base(options)
        {}

        public DbSet<Person> Persons{ get; set; }
    }

    protected override void BuildModel(ModelBuilder modelBuilder)
    {
        modelBuilder
            .HasAnnotation("ProductVersion", "7.0.0-rc1-16348")
            .HasAnnotation("SqlServer:ValueGenerationStrategy", SqlServerValueGenerationStrategy.IdentityColumn);

        modelBuilder.Entity("EFTimestampBug.Models.Person", b =>
            {
                b.Property<int>("Id")
                    .ValueGeneratedOnAdd();

                b.Property<byte[]>("Timestamp")
                    .IsConcurrencyToken()
                    .ValueGeneratedOnAddOrUpdate();

                b.Property<string>("Title");

                b.HasKey("Id");
            });
    }

    // PUT api/values/5
    [HttpPut("{id}")]
    public Person Put(int id, [FromBody]Person personDTO)
    {
        // 7
        var person = db.Persons.SingleOrDefault(x => x.Id == id);
        person.Title = personDTO.Title;
        person.Timestamp = personDTO.Timestamp;
        db.SaveChanges();
        return person;
    }

    [Fact]
    public async Task Fail_When_Timestamp_Differs()
    {
        using (var client = server.CreateClient().AcceptJson())
        {
            await client.PostAsJsonAsync(ApiEndpoint, Persons[0]);
            // 1
            var getResponse = await client.GetAsync(ApiEndpoint);
            var fetched = await getResponse.Content.ReadAsJsonAsync<List<Person>>();

            Assert.True(getResponse.IsSuccessStatusCode);
            Assert.NotEmpty(fetched);

            var person = fetched.First();
            // 2
            var fromDb = await db.Persons.SingleOrDefaultAsync(x => x.Id == person.Id);
            // 3
            fromDb.Title = "In between";
            // 4
            await db.SaveChangesAsync();


            // 5
            person.Title = "After - should fail";
            // 6
            var postResponse = await client.PutAsJsonAsync(ApiEndpoint + person.Id, person);
            var created = await postResponse.Content.ReadAsJsonAsync<Person>();

            Assert.False(postResponse.IsSuccessStatusCode);
        }
    }


    // generated sql - @p1 has the original timestamp from the entity and not the assigned and therefore the save succeed which was not intended
    exec sp_executesql N'SET NOCOUNT OFF;
    UPDATE[Person] SET[Title] = @p2
    OUTPUT INSERTED.[Timestamp]
    WHERE [Id] = @p0 AND[Timestamp] = @p1;
    ',N'@p0 int,@p1 varbinary(8),@p2 nvarchar(4000)',@p0=21,@p1=0x00000000000007F4,@p2=N'After - should fail'

Answer 1

编辑4-修复

我从GitHub repo 网站issue 4512的成员那里收到回音。您必须更新实体上的原始值。可以这样做。

var passedInTimestamp = new byte[] { 0, 0, 0, 0, 0, 0, 0, 120 };  // a hard coded value but normally included in a postback
var entryProp = db.Entry(person).Property(u => u.Timestamp);
entryProp.OriginalValue = passedInTimestamp;

我已经更新了原始单元测试，该单元测试在您和我无法引发 DbUpdateConcurrencyException的地方失败，现在可以按预期运行了。

我将更新GitHub票证，询问他们是否可以进行更改，以便在将该列标记为 Timestamp或 IsConcurrencyToken时，生成的基础sql使用新值而不是原始值，以使其行为类似于的先前版本。 Entity Framework 。

就目前而言，这似乎是使用分离的实体执行此操作的方法。

编辑＃3

谢谢，我错过了。经过更多的调试后，我完全理解了这个问题，尽管不是为什么会发生。不过，我们可能应该从中删除Web API，减少事件部分，并且我认为EF Core和Web API之间没有直接的依赖关系。我用以下说明问题的测试重现了该问题。我不愿意将其称为错误，因为自EF6以来，强制EF Core使用传入的 timestamp值的约定已发生更改。

我已经在该项目的GitHub网站上创建了一套完整的工作最小代码和 created an issue/question。我将在下面再次包含该测试以供引用。收到回复后，我会立即回覆此答案，并告诉您。

依存关系

SQL Server 2012年

EF核心

EntityFramework.Commands 7.0.0-rc1-final

EntityFramework.MicrosoftSqlServer 7.0.0-rc1-final

DDL

CREATE TABLE [dbo].[Person](
    [Id] [int] IDENTITY NOT NULL,
    [Title] [varchar](50) NOT NULL,
    [Timestamp] [rowversion] NOT NULL,
 CONSTRAINT [PK_Person] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
))
INSERT INTO Person (title) values('user number 1')

实体

public class Person
{
    public int Id { get; set; }

    public String Title { get; set; }

    // [Timestamp], tried both with & without annotation
    public byte[] Timestamp { get; set; }
}

Db上下文

public class Context : DbContext
{
    public Context(DbContextOptions options)
        : base(options)
    {
    }

    public DbSet<Person> Persons { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Person>().HasKey(x => x.Id);

        modelBuilder.Entity<Person>().Property(x => x.Id)
            .UseSqlServerIdentityColumn()
            .ValueGeneratedOnAdd()
            .ForSqlServerHasColumnName("Id");

        modelBuilder.Entity<Person>().Property(x => x.Title)
            .ForSqlServerHasColumnName("Title");

        modelBuilder.Entity<Person>().Property(x => x.Timestamp)
            .IsConcurrencyToken(true)
            .ValueGeneratedOnAddOrUpdate()
            .ForSqlServerHasColumnName("Timestamp");

        base.OnModelCreating(modelBuilder);
    }
}

单元测试

public class UnitTest
{
    private string dbConnectionString = "DbConnectionStringOrConnectionName";
    public EFTimestampBug.Models.Context CreateContext()
    {
        var options = new DbContextOptionsBuilder();
        options.UseSqlServer(dbConnectionString);
        return new EFTimestampBug.Models.Context(options.Options);
    }

    [Fact] // this test passes
    public async Task TimestampChangedExternally()
    {
        using (var db = CreateContext())
        {
            var person = await db.Persons.SingleAsync(x => x.Id == 1);
            person.Title = "Update 2 - should fail";

            // update the database manually after we have a person instance
            using (var connection = new System.Data.SqlClient.SqlConnection(dbConnectionString))
            {
                var command = connection.CreateCommand();
                command.CommandText = "update person set title = 'changed title' where id = 1";
                connection.Open();
                await command.ExecuteNonQueryAsync();
                command.Dispose();
            }

            // should throw exception
            try
            {
                await db.SaveChangesAsync();
                throw new Exception("should have thrown exception");
            }
            catch (DbUpdateConcurrencyException)
            {
            }
        }
    }

    [Fact]
    public async Task EmulateAspPostbackWhereTimestampHadBeenChanged()
    {
        using (var db = CreateContext())
        {
            var person = await db.Persons.SingleAsync(x => x.Id == 1);
            person.Title = "Update 2 - should fail " + DateTime.Now.Second.ToString();

            // This emulates post back where the timestamp is passed in from the web page
            // the Person entity attached dbcontext does have the latest timestamp value but
            // it needs to be changed to what was posted
            // this way the user would see that something has changed between the time that their screen initially loaded and the time they posted the form back
            var passedInTimestamp = new byte[] { 0, 0, 0, 0, 0, 0, 0, 120 };  // a hard coded value but normally included in a postback
            //person.Timestamp = passedInTimestamp;
            var entry = db.Entry(person).Property(u => u.Timestamp);
            entry.OriginalValue = passedInTimestamp;
            try
            {
                await db.SaveChangesAsync(); // EF ignores the set Timestamp value and uses its own value in the outputed sql
                throw new Exception("should have thrown DbUpdateConcurrencyException");
            }
            catch (DbUpdateConcurrencyException)
            {
            }
        }
    }
}