c#

我正在使用 .net 5 实现一个 api。我有一个学生类，它有一个地址类型的属性（根据 ddd 的值对象）。

public class Student 
{
        public long Id{ get; private set; }
        public string FirstName { get; private set; }
        public string LastName { get; private set; }
        public Address Address { get; private set; }
}

public class Address
{
    public string City { get; private set; }
    public string Road { get; private set; }
}

我正在使用 fluent api 使用 ef core 5 配置数据库。

 class StudentConfiguration : IEntityTypeConfiguration<Student>
    {

        public void Configure(EntityTypeBuilder<Student> builder)
        {
            builder.ToTable("Students");
            builder.HasKey(x => x.Id);

            builder.Property(x => x.Id).ValueGeneratedNever().IsRequired();
            builder.Property(x => x.FirstName).HasMaxLength(25).IsRequired();
            builder.Property(x => x.LastName).HasMaxLength(50).IsRequired();           


            builder.OwnsOne(x => x.Address, x =>
            {
                x.Property(pp => pp.City)
                    .IsRequired()
                    .HasColumnName("City")
                    .HasMaxLength(20);
                x.Property(pp => pp.Road)
                    .IsRequired()
                    .HasColumnName("Road")
                    .HasMaxLength(40);
            });

        }
    }

因此，我有一张表，其中包含 Id、Fistname、lastname、city、road 列。

现在我试图只更新城市和道路（例如学生更衣室），但我有不同的例外，我不知道如何只更新这两列

public async Task UpdateAddress(Student student)
{
//Firts try 
            //var studentEntry = context.Entry(student);
            //studentEntry.Property(x => x.Address.City).IsModified = true;
            //studentEntry.Property(x => x.Address.Road).IsModified = true;
            //**Exception** 'The expression 'x => x.Address.City' is not a valid member access expression. The expression should represent a simple property or field access: 't => t.MyProperty'. (Parameter 'memberAccessExpression')'

//Second try 
             //var studentEntry = context.Entry(student.Address);
            //studentEntry.Property(x => x.City).IsModified = true;
            //studentEntry.Property(x => x.Road).IsModified = true;
            //**Exception** 'Database operation expected to affect 1 row(s) but actually affected 0 row(s). Data may have been modified or deleted since entities were loaded. 

//the only method that works is Update but this update the whole object
     context.Update(student);
     await context.SaveChangesAsync();
}

编辑

public class StudentDbContext : DbContext
    {
        public DbSet<Student> Students { get; set; }

        public StudentDbContext(DbContextOptions<StudentDbContext> options) : base(options)
        {
            ChangeTracker.QueryTrackingBehavior = QueryTrackingBehavior.NoTracking;
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.ApplyConfigurationsFromAssembly(Assembly.GetExecutingAssembly());
            base.OnModelCreating(modelBuilder);
        }
    }

如何仅更新拥有实体的这两个属性？

回答

var studentEntry = context.Attach(student);

var addressEntry = studentEntry.Reference(e => e.Address);
addressEntry.TargetEntry.Property(e => e.City).IsModified = true;
addressEntry.TargetEntry.Property(e => e.Road).IsModified = true;