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變更追蹤器偵錯

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Entity Framework Core （EF Core） 變更追蹤器會產生兩種輸出，以協助偵錯：

  • ChangeTracker.DebugView提供所追蹤之所有實體的人類可讀取檢視
  • 當變更追蹤器偵測到狀態並修正關聯性時，會產生偵錯層級記錄訊息

提示

本檔假設瞭解實體狀態和 EF Core 變更追蹤的基本概念。 如需這些主題的詳細資訊，請參閱 EF Core 中的變更追蹤。

提示

您可以從 GitHub 下載範例程式碼，以執行並偵錯此文件中的所有程式碼。

變更追蹤器偵錯檢視

您可以在 IDE 的偵錯工具中存取變更追蹤器偵錯檢視。 例如，使用 Visual Studio：

Accessing the change tracker debug view from the Visual Studio debugger

它也可以直接從程式碼存取，例如將偵錯檢視傳送至主控台：

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

偵錯檢視有簡短表單和長表單。 簡短表單會顯示追蹤的實體、其狀態和索引鍵值。 長表單也包含所有屬性和導覽值和狀態。

簡短檢視

讓我們看看使用本檔結尾所顯示模型的偵錯檢視範例。 首先，我們將追蹤某些實體，並將其置於一些不同的狀態，因此我們有良好的變更追蹤資料來檢視：

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();

此時列印簡短檢視，如上所示，會產生下列輸出：

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：

  • 每個追蹤實體都會以其主鍵 （PK） 值列出。 例如： Blog {Id: 1} 。
  • 如果實體是共用類型實體類型，也會顯示其 CLR 類型。 例如： PostTag (Dictionary<string, object>) 。
  • 接下來 EntityState 會顯示 。 這會是 、 Added 、 Modified 或 Deleted 的 Unchanged 其中一個。
  • 接下來會顯示任何替代索引鍵 （AKs） 的值。 例如： AK {AssetsId: ed727978-1ffe-4709-baee-73913e8e44a0} 。
  • 最後，會顯示任何外鍵 （FK） 的值。 例如： FK {PostsId: 4} FK {TagsId: 2} 。

長檢視

長檢視可以與簡短檢視相同的方式傳送至主控台：

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

與上述簡短檢視相同狀態的輸出為：

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}]

每個追蹤實體及其狀態都會如先前所示。 不過，長檢視也會顯示內容和導覽值。

屬性值

對於每個屬性，長檢視會顯示 屬性是否為主鍵 （PK）、 替代索引鍵 （AK） 或外鍵 （FK） 的一部分。 例如：

  • Blog.Id 是主鍵屬性： Id: 1 PK
  • Blog.AssetsId 是替代索引鍵屬性： AssetsId: 'ed727978-1ffe-4709-baee-73913e8e44a0' AK
  • Post.BlogId 是外鍵屬性： BlogId: 2 FK
  • BlogAssets.Id 是主鍵和外鍵屬性： Id: '3a54b880-2b9d-486b-9403-dc2e52d36d65' PK FK

已修改的屬性值會標示為這類值，也會顯示內容的原始值。 例如： Name: '.NET Blog (All new!)' Modified Originally '.NET Blog' 。

最後， Added 具有暫存索引鍵值的實體表示值是暫時的。 例如： Id: -2147482643 PK Temporary 。

導覽值是使用導覽參考之實體的主鍵值來顯示。 例如，在上述輸出中，文章 3 與部落格 2 相關。 這表示導覽 Post.Blog 會指向識別碼為 2 的 Blog 實例。 這會顯示為 Blog: {Id: 2} 。

集合導覽會發生相同的情況，不同之處在于在此情況下，可能會有多個相關的實體。 例如，集合導覽 Blog.Posts 包含三個實體，索引鍵值分別為 1、2 和 -2147482643。 這會顯示為 [{Id: 1}, {Id: 2}, {Id: -2147482643}] 。

變更追蹤器記錄

每當變更追蹤器偵測到屬性或流覽變更時， 就會在 記錄訊息。 DebugLogLevel 例如，當 ChangeTracker.DetectChanges() 在此檔頂端的程式碼中呼叫 ，並 啟用 偵錯記錄時，會產生下列記錄：

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'.

下表摘要變更追蹤器記錄訊息：

事件識別碼 描述
CoreEventId.DetectChangesStarting DetectChanges() 正在啟動
CoreEventId.DetectChangesCompleted DetectChanges() 已完成
CoreEventId.PropertyChangeDetected 一般屬性值已變更
CoreEventId.ForeignKeyChangeDetected 外鍵屬性值已變更
CoreEventId.CollectionChangeDetected 非略過集合導覽已新增或移除相關的實體。
CoreEventId.ReferenceChangeDetected 參考導覽已變更為指向另一個實體，或設定為 null
CoreEventId.StartedTracking EF Core 已開始追蹤實體
CoreEventId.StateChanged EntityState實體的 已變更
CoreEventId.ValueGenerated 已為屬性產生值
CoreEventId.SkipCollectionChangeDetected 略過集合導覽已新增或移除相關的實體

模型

上述範例所使用的模型包含下列實體類型：

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
}

此模型大部分是依照慣例來設定，OnModelCreating 中只有幾行：

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);
}