更改跟踪器调试

项目
10/05/2023

Entity Framework Core (EF Core) 更改跟踪器会生成两种类型的输出以帮助进行调试：

ChangeTracker.DebugView 提供了有关要跟踪的所有实体的直观易懂的视图
更改跟踪器检测到状态并修复关系时，将生成调试级别日志消息

提示

本文档假设你已了解实体状态和 EF Core 更改跟踪的基础知识。有关这些主题的详细信息，请参阅 EF Core 中的更改跟踪。

提示

通过从 GitHub 下载示例代码，你可运行并调试到本文档中的所有代码。

更改跟踪器调试视图

可以在 IDE 的调试器中访问更改跟踪器调试视图。例如，在 Visual Studio 中：

从 Visual Studio 调试程序访问更改跟踪器视图

也可以直接通过代码访问它，例如，将调试视图发送到控制台：

Console.WriteLine(context.ChangeTracker.DebugView.ShortView);

调试视图具有短视图形式和长视图形式。短视图形式显示跟踪的实体、它们的状态和键值。长视图形式还包括所有属性以及导航值和状态。

短视图

我们来查看使用本文档末尾所示的模型进行的一个调试视图示例。首先，我们将跟踪一些实体，并使它们处于不同的状态，以便可以查看良好的更改跟踪数据：

using var context = new BlogsContext();

var blogs = context.Blogs
    .Include(e => e.Posts).ThenInclude(e => e.Tags)
    .Include(e => e.Assets)
    .ToList();

// Mark something Added
blogs[0].Posts.Add(
    new Post
    {
        Title = "What’s next for System.Text.Json?",
        Content = ".NET 5.0 was released recently and has come with many new features and..."
    });

// Mark something Deleted
blogs[1].Posts.Remove(blogs[1].Posts[1]);

// Make something Modified
blogs[0].Name = ".NET Blog (All new!)";

context.ChangeTracker.DetectChanges();

如上所示，此时打印短视图将产生以下输出：

Blog {Id: 1} Modified AK {AssetsId: ed727978-1ffe-4709-baee-73913e8e44a0}
Blog {Id: 2} Unchanged AK {AssetsId: 3a54b880-2b9d-486b-9403-dc2e52d36d65}
BlogAssets {Id: 3a54b880-2b9d-486b-9403-dc2e52d36d65} Unchanged FK {Id: 3a54b880-2b9d-486b-9403-dc2e52d36d65}
BlogAssets {Id: ed727978-1ffe-4709-baee-73913e8e44a0} Unchanged FK {Id: ed727978-1ffe-4709-baee-73913e8e44a0}
Post {Id: -2147482643} Added FK {BlogId: 1}
Post {Id: 1} Unchanged FK {BlogId: 1}
Post {Id: 2} Unchanged FK {BlogId: 1}
Post {Id: 3} Unchanged FK {BlogId: 2}
Post {Id: 4} Deleted FK {BlogId: 2}
PostTag (Dictionary<string, object>) {PostsId: 1, TagsId: 1} Unchanged FK {PostsId: 1} FK {TagsId: 1}
PostTag (Dictionary<string, object>) {PostsId: 1, TagsId: 3} Unchanged FK {PostsId: 1} FK {TagsId: 3}
PostTag (Dictionary<string, object>) {PostsId: 2, TagsId: 1} Unchanged FK {PostsId: 2} FK {TagsId: 1}
PostTag (Dictionary<string, object>) {PostsId: 3, TagsId: 2} Unchanged FK {PostsId: 3} FK {TagsId: 2}
PostTag (Dictionary<string, object>) {PostsId: 4, TagsId: 2} Deleted FK {PostsId: 4} FK {TagsId: 2}
Tag {Id: 1} Unchanged
Tag {Id: 2} Unchanged
Tag {Id: 3} Unchanged

注意：

每个跟踪实体都列出了其主键 (PK) 值。例如 Blog {Id: 1}。
如果实体是共享类型实体类型，则还会显示其 CLR 类型。例如 PostTag (Dictionary<string, object>)。
接下来会显示 EntityState。这将是以下状态之一：Unchanged、Added、Modified 或 Deleted。
接下来将显示任何替代键 (AK) 的值。例如 AK {AssetsId: ed727978-1ffe-4709-baee-73913e8e44a0}。
最后，将显示任何外键 (FK) 的值。例如 FK {PostsId: 4} FK {TagsId: 2}。

长视图

可以通过与短视图相同的方式，将长视图发送到控制台：

Console.WriteLine(context.ChangeTracker.DebugView.LongView);

与上文中短视图相同的状态的输出为：

Blog {Id: 1} Modified
  Id: 1 PK
  AssetsId: 'ed727978-1ffe-4709-baee-73913e8e44a0' AK
  Name: '.NET Blog (All new!)' Modified Originally '.NET Blog'
  Assets: {Id: ed727978-1ffe-4709-baee-73913e8e44a0}
  Posts: [{Id: 1}, {Id: 2}, {Id: -2147482643}]
Blog {Id: 2} Unchanged
  Id: 2 PK
  AssetsId: '3a54b880-2b9d-486b-9403-dc2e52d36d65' AK
  Name: 'Visual Studio Blog'
  Assets: {Id: 3a54b880-2b9d-486b-9403-dc2e52d36d65}
  Posts: [{Id: 3}]
BlogAssets {Id: 3a54b880-2b9d-486b-9403-dc2e52d36d65} Unchanged
  Id: '3a54b880-2b9d-486b-9403-dc2e52d36d65' PK FK
  Banner: <null>
  Blog: {Id: 2}
BlogAssets {Id: ed727978-1ffe-4709-baee-73913e8e44a0} Unchanged
  Id: 'ed727978-1ffe-4709-baee-73913e8e44a0' PK FK
  Banner: <null>
  Blog: {Id: 1}
Post {Id: -2147482643} Added
  Id: -2147482643 PK Temporary
  BlogId: 1 FK
  Content: '.NET 5.0 was released recently and has come with many new fe...'
  Title: 'What's next for System.Text.Json?'
  Blog: {Id: 1}
  Tags: []
Post {Id: 1} Unchanged
  Id: 1 PK
  BlogId: 1 FK
  Content: 'Announcing the release of EF Core 5.0, a full featured cross...'
  Title: 'Announcing the Release of EF Core 5.0'
  Blog: {Id: 1}
  Tags: [{Id: 1}, {Id: 3}]
Post {Id: 2} Unchanged
  Id: 2 PK
  BlogId: 1 FK
  Content: 'F# 5 is the latest version of F#, the functional programming...'
  Title: 'Announcing F# 5'
  Blog: {Id: 1}
  Tags: [{Id: 1}]
Post {Id: 3} Unchanged
  Id: 3 PK
  BlogId: 2 FK
  Content: 'If you are focused on squeezing out the last bits of perform...'
  Title: 'Disassembly improvements for optimized managed debugging'
  Blog: {Id: 2}
  Tags: [{Id: 2}]
Post {Id: 4} Deleted
  Id: 4 PK
  BlogId: 2 FK
  Content: 'Examine when database queries were executed and measure how ...'
  Title: 'Database Profiling with Visual Studio'
  Blog: <null>
  Tags: [{Id: 2}]
PostTag (Dictionary<string, object>) {PostsId: 1, TagsId: 1} Unchanged
  PostsId: 1 PK FK
  TagsId: 1 PK FK
PostTag (Dictionary<string, object>) {PostsId: 1, TagsId: 3} Unchanged
  PostsId: 1 PK FK
  TagsId: 3 PK FK
PostTag (Dictionary<string, object>) {PostsId: 2, TagsId: 1} Unchanged
  PostsId: 2 PK FK
  TagsId: 1 PK FK
PostTag (Dictionary<string, object>) {PostsId: 3, TagsId: 2} Unchanged
  PostsId: 3 PK FK
  TagsId: 2 PK FK
PostTag (Dictionary<string, object>) {PostsId: 4, TagsId: 2} Deleted
  PostsId: 4 PK FK
  TagsId: 2 PK FK
Tag {Id: 1} Unchanged
  Id: 1 PK
  Text: '.NET'
  Posts: [{Id: 1}, {Id: 2}]
Tag {Id: 2} Unchanged
  Id: 2 PK
  Text: 'Visual Studio'
  Posts: [{Id: 3}, {Id: 4}]
Tag {Id: 3} Unchanged
  Id: 3 PK
  Text: 'EF Core'
  Posts: [{Id: 1}]

每个跟踪的实体及其状态都将按原来的方式显示。但是，长视图还会显示属性和导航值。

属性值

对于每个属性，长视图会显示属性是否是主键 (PK)、替代键 (AK) 或外键 (FK) 的一部分。例如：

Blog.Id 是主键属性：Id: 1 PK
Blog.AssetsId 是替代键属性：AssetsId: 'ed727978-1ffe-4709-baee-73913e8e44a0' AK
Post.BlogId 是外键属性：BlogId: 2 FK
BlogAssets.Id 既是主键又是外键属性：Id: '3a54b880-2b9d-486b-9403-dc2e52d36d65' PK FK

修改过的属性值都将以此方式进行标记，并且还会显示属性的原始值。例如 Name: '.NET Blog (All new!)' Modified Originally '.NET Blog'。

最后，具有临时键值的 Added 实体将表明该值是临时值。例如 Id: -2147482643 PK Temporary。

导航值是使用导航引用的实体的主键值显示的。例如，在上面的输出中，post 3 与 blog 2 相关。这意味着 Post.Blog 导航指向 ID 为 2 的 Blog 实例。这可以表示为 Blog: {Id: 2}。

集合导航也发生相同的情况，只是在这种情况下，可能有多个相关实体。例如，集合导航 Blog.Posts 包含三个实体，它们的键值分别为 1、2 和 -2147482643。这可以表示为 [{Id: 1}, {Id: 2}, {Id: -2147482643}]。

更改跟踪器日志记录

每当检测到属性或导航更改时，更改跟踪器会在 Debug LogLevel 记录消息。例如，在本文档顶部的代码中调用 ChangeTracker.DetectChanges() 并启用调试日志记录时，将生成以下日志：

dbug: 12/30/2020 13:52:44.815 CoreEventId.DetectChangesStarting[10800] (Microsoft.EntityFrameworkCore.ChangeTracking)
      DetectChanges starting for 'BlogsContext'.
dbug: 12/30/2020 13:52:44.818 CoreEventId.PropertyChangeDetected[10802] (Microsoft.EntityFrameworkCore.ChangeTracking)
      The unchanged property 'Blog.Name' was detected as changed from '.NET Blog' to '.NET Blog (All new!)' and will be marked as modified for entity with key '{Id: 1}'.
dbug: 12/30/2020 13:52:44.820 CoreEventId.StateChanged[10807] (Microsoft.EntityFrameworkCore.ChangeTracking)
      The 'Blog' entity with key '{Id: 1}' tracked by 'BlogsContext' changed state from 'Unchanged' to 'Modified'.
dbug: 12/30/2020 13:52:44.821 CoreEventId.CollectionChangeDetected[10804] (Microsoft.EntityFrameworkCore.ChangeTracking)
      1 entities were added and 0 entities were removed from navigation 'Blog.Posts' on entity with key '{Id: 1}'.
dbug: 12/30/2020 13:52:44.822 CoreEventId.ValueGenerated[10808] (Microsoft.EntityFrameworkCore.ChangeTracking)
      'BlogsContext' generated temporary value '-2147482638' for the property 'Id.Post'.
dbug: 12/30/2020 13:52:44.822 CoreEventId.StartedTracking[10806] (Microsoft.EntityFrameworkCore.ChangeTracking)
      Context 'BlogsContext' started tracking 'Post' entity with key '{Id: -2147482638}'.
dbug: 12/30/2020 13:52:44.827 CoreEventId.CollectionChangeDetected[10804] (Microsoft.EntityFrameworkCore.ChangeTracking)
      0 entities were added and 1 entities were removed from navigation 'Blog.Posts' on entity with key '{Id: 2}'.
dbug: 12/30/2020 13:52:44.827 CoreEventId.StateChanged[10807] (Microsoft.EntityFrameworkCore.ChangeTracking)
      The 'Post' entity with key '{Id: 4}' tracked by 'BlogsContext' changed state from 'Unchanged' to 'Modified'.
dbug: 12/30/2020 13:52:44.829 CoreEventId.CascadeDeleteOrphan[10003] (Microsoft.EntityFrameworkCore.Update)
      An entity of type 'Post' with key '{Id: 4}' changed to 'Deleted' state due to severed required relationship to its parent entity of type 'Blog'.
dbug: 12/30/2020 13:52:44.829 CoreEventId.StateChanged[10807] (Microsoft.EntityFrameworkCore.ChangeTracking)
      The 'Post' entity with key '{Id: 4}' tracked by 'BlogsContext' changed state from 'Modified' to 'Deleted'.
dbug: 12/30/2020 13:52:44.829 CoreEventId.CollectionChangeDetected[10804] (Microsoft.EntityFrameworkCore.ChangeTracking)
      0 entities were added and 1 entities were removed from navigation 'Blog.Posts' on entity with key '{Id: 2}'.
dbug: 12/30/2020 13:52:44.831 CoreEventId.CascadeDelete[10002] (Microsoft.EntityFrameworkCore.Update)
      A cascade state change of an entity of type 'PostTag' with key '{PostsId: 4, TagsId: 2}' to 'Deleted' occurred due to the deletion of its parent entity of type 'Post' with key '{Id: 4}'.
dbug: 12/30/2020 13:52:44.831 CoreEventId.StateChanged[10807] (Microsoft.EntityFrameworkCore.ChangeTracking)
      The 'PostTag' entity with key '{PostsId: 4, TagsId: 2}' tracked by 'BlogsContext' changed state from 'Unchanged' to 'Deleted'.
dbug: 12/30/2020 13:52:44.831 CoreEventId.DetectChangesCompleted[10801] (Microsoft.EntityFrameworkCore.ChangeTracking)
      DetectChanges completed for 'BlogsContext'.

下表汇总了更改跟踪器日志记录消息：

事件 ID	说明
CoreEventId.DetectChangesStarting	DetectChanges() 正在启动
CoreEventId.DetectChangesCompleted	DetectChanges() 已完成
CoreEventId.PropertyChangeDetected	常规属性值已更改
CoreEventId.ForeignKeyChangeDetected	外键属性值已更改
CoreEventId.CollectionChangeDetected	非跳过集合导航已添加或删除相关实体。
CoreEventId.ReferenceChangeDetected	引用导航已更改为指向另一个实体，或设置为 null
CoreEventId.StartedTracking	EF Core 已开始跟踪实体
CoreEventId.StateChanged	实体的 EntityState 已更改
CoreEventId.ValueGenerated	已为属性生成了值
CoreEventId.SkipCollectionChangeDetected	跳过集合导航已添加或删除相关实体

模型

用于上述示例的模型包含以下实体类型：

public class Blog
{
    public int Id { get; set; } // Primary key
    public Guid AssetsId { get; set; } // Alternate key
    public string Name { get; set; }

    public IList<Post> Posts { get; } = new List<Post>(); // Collection navigation
    public BlogAssets Assets { get; set; } // Reference navigation
}

public class BlogAssets
{
    public Guid Id { get; set; } // Primary key and foreign key
    public byte[] Banner { get; set; }

    public Blog Blog { get; set; } // Reference navigation
}

public class Post
{
    public int Id { get; set; } // Primary key
    public string Title { get; set; }
    public string Content { get; set; }

    public int BlogId { get; set; } // Foreign key
    public Blog Blog { get; set; } // Reference navigation

    public IList<Tag> Tags { get; } = new List<Tag>(); // Skip collection navigation
}

public class Tag
{
    public int Id { get; set; } // Primary key
    public string Text { get; set; }

    public IList<Post> Posts { get; } = new List<Post>(); // Skip collection navigation
}

模型主要通过约定配置，在 OnModelCreating 中只有几行：

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder
        .Entity<Blog>()
        .Property(e => e.AssetsId)
        .ValueGeneratedOnAdd();

    modelBuilder
        .Entity<BlogAssets>()
        .HasOne(e => e.Blog)
        .WithOne(e => e.Assets)
        .HasForeignKey<BlogAssets>(e => e.Id)
        .HasPrincipalKey<Blog>(e => e.AssetsId);
}

通过

更改跟踪器调试

更改跟踪器调试视图

短视图

长视图

属性值

导航值

更改跟踪器日志记录

模型

其他资源