EF Core First 预加载继承筛选器

Question

我定义了以下实体：

public class Computer
{
    [Key]
    public int Id { get; set; }

    [Required]
    [StringLength(15)]
    public string Name { get; set; } = null!;

    [Required]
    public List<ComputerAction> Actions { get; set; } = new();
}

public abstract class ComputerAction
{
    [Key]
    public int Id { get; set; }

    public List<HistoryEntry> History { get; set; } = new();

    public Computer Computer { get; set; } = null!;

    [NotMapped]
    public Status Status => History.LastOrDefault()?.Status ?? Status.Unknown;

    public abstract Task<HistoryEntry> ExecuteAsync();
}

public class RenewCertificateAction : ComputerAction
{
    public override Task<HistoryEntry> ExecuteAsync() 
    {
        // Whatever
    }
}

public class PingAction : ComputerAction
{
    private readonly Ping _ping = new();

    public override async Task<HistoryEntry> ExecuteAsync()
    {
        // Whatever
    }
}

public class HistoryEntry
{
    [Key]
    public int Id { get; set; }

    [Required]
    public Status Status { get; set; }

    [Required]
    public DateTime WhenExecuted { get; set; }
}

而我的 DbContext 如下：

public class ComputerContext : DbContext
{
    public ComputerContext(DbContextOptions<ComputerContext> options)
        : base(options)
    {
    }

    public static readonly string ComputerDb = nameof(ComputerDb);

    public DbSet<Computer> Computers { get; set; } = null!;

    public DbSet<RenewCertificateAction> RenewCertificateActions { get; set; } = null!;

    public DbSet<PingAction> PingActions { get; set; } = null!;

    public DbSet<HistoryEntry> History { get; set; } = null!;

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Computer>().HasMany(x => x.Actions).WithOne(x => x.Computer).OnDelete(DeleteBehavior.Cascade);
        modelBuilder.Entity<ComputerAction>().ToTable("ComputerActions").HasMany(x => x.History).WithOne().OnDelete(DeleteBehavior.Cascade);
        modelBuilder.Entity<HistoryEntry>().ToTable("ComputerActionEntries");
    }
}

我想获取所有计算机的列表，但如果它们碰巧有类型为 PingAction 的操作，则也加载该操作（并且仅加载该操作，而不是所有操作）。

对我来说合乎逻辑的是 dbContext.Computers.Include(x => x.Actions.OfType<PingAction>()) 之类的东西，但显然不能将其转换为查询。我怎样才能只对特定类型的 Actions 执行 Include？

Answer 1

你可以使用where里面的include:

dbContext.Computers.Include(x => x.Actions.Where(action => action is PingAction))

更多解释：：

EF Core First 预加载继承筛选器

EF Core First Eager Loading Inheritance Filter

.net

c#

entity-framework