我覆盖了 SaveChanges 方法来审核 EntityFramework 中的更改。在我尝试更新关联对象之前，它工作正常。当我尝试更新关联对象时，我得到 ArgumentException。我发现从 ChangeTracker 读取实体后会引发异常。如果我在覆盖的 SaveChanges 方法中对 ChangeTracker 不执行任何操作，则对象将成功更新。我使用 EntityFramework 5.0。
你不知道这是一个错误还是我做错了什么？
抛出异常：
System.ArgumentException 被捕获 HResult=-2147024809
Message=定义 EntityKey 的键值对不能为 null 或空。参数名称：记录 Source=System.Data.Entity
ParamName=record StackTrace：在 System.Data.EntityKey.GetKeyValues(EntitySet entitySet, IExtendedDataRecord record, String[]& keyNames, Object& singletonKeyValue, Object[]&compositeKeyValues) at System.Data .EntityKey..ctor(EntitySet entitySet, IExtendedDataRecord 记录) 在 System.Data.Objects.ObjectStateManager.PerformDelete(IList1 entries) at System.Data.Objects.ObjectStateManager.DetectChanges() at System.Data.Objects.ObjectContext.DetectChanges() at System.Data.Entity.Internal.InternalContext.DetectChanges(Boolean force) at System.Data.Entity.Internal.InternalContext.GetStateEntries(Func2 谓词）在 System.Data.Entity.Infrastructure.DbChangeTracker.Entries() 的 System.Data.Entity.Internal.InternalContext.GetStateEntries() 在 System.Data.Entity.DbContext.GetValidationErrors() 在 System.Data.Entity。 Internal.InternalContext.SaveChanges() 在 System.Data.Entity.Internal.LazyInternalContext.SaveChanges() 在 System.Data.Entity.DbContext.SaveChanges() 在 EFTest2.BlogContext.SaveChanges() 在 c:\Projects\EF22\EFTest2Solution \EFTest2\Context.cs：EFTest2.Program.Main(String[] args) 中的第 37 行：\Projects\EF22\EFTest2Solution\EFTest2\Program.cs:第 42 行
我的代码是这样的：Program.cs
class Program
{
static void Main(string[] args)
{
var configuration = new Configuration();
configuration.TargetDatabase = new DbConnectionInfo("Data Source=server;Initial Catalog=EntityFramework;Integrated Security=True", "System.Data.SqlClient");
var migrator = new DbMigrator(configuration);
var scriptor = new MigratorScriptingDecorator(migrator);
var script = scriptor.ScriptUpdate(sourceMigration: null, targetMigration: null);
Console.WriteLine(script);
var pending = migrator.GetPendingMigrations();
migrator.Update();
using (var ctx = new BlogContext())
{
Post post = new Post { Content = "Content", SpecialBlog = new Blog() { Title = "SpecialBlog" } };
ctx.Posts.Add(post);
ctx.SaveChanges();
post.SpecialBlog = new Blog() { Title = "Update SpecialBlog" };
ctx.SaveChanges(); // ArgumentException is thrown when using ChangeTracker
}
}
}
模型
public class Blog
{
public int? BlogId { get; set; }
public string Title { get; set; }
public ICollection<Post> Posts { get; set; }
}
public partial class BlogMap : EntityTypeConfiguration<Blog>
{
public BlogMap()
: base()
{
HasKey(c => c.BlogId);
Property(c => c.Title).IsRequired().HasMaxLength(40);
ToTable("Blog");
}
}
public class Post
{
public int? PostId { get; set; }
public string Content { get; set; }
public int? BlogId { get; set; }
public Blog Blog { get; set; }
public int? SpecialBlogId { get; set; }
public Blog SpecialBlog { get; set; }
}
public partial class PostMap : EntityTypeConfiguration<Post>
{
public PostMap()
: base()
{
HasKey(c => c.PostId);
Property(c => c.Content);
HasOptional(m => m.Blog)
.WithMany(t => t.Posts)
.HasForeignKey(m => m.BlogId)
.WillCascadeOnDelete(false);
HasOptional(m => m.SpecialBlog)
.WithMany()
.HasForeignKey(m => m.SpecialBlogId)
.WillCascadeOnDelete(false);
ToTable("Post");
}
}
语境：
public class BlogContext : DbContext
{
public DbSet<Blog> Blogs { get; set; }
public DbSet<Post> Posts { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
Database.SetInitializer(new DropCreateDatabaseAlways<BlogContext>());
modelBuilder.Configurations.Add(new PostMap());
modelBuilder.Configurations.Add(new BlogMap());
}
public override int SaveChanges()
{
var entries = ChangeTracker.Entries(); // causes ArgumentNullException after calling base.SaveChanges();
return base.SaveChanges();
}
}
配置
public class Configuration : DbMigrationsConfiguration<BlogContext>
{
public Configuration()
{
AutomaticMigrationsEnabled = true;
AutomaticMigrationDataLossAllowed = true;
}
}