Question

我试图设置一个相当复杂的数据模型，并且尽管sql方面非常直接，但是我在我的数据库中的流畅配置中遇到了一个奇怪的问题上下文。

我所拥有的是3个表，其中2个表共享一个名为tasks的公用表，如下所示：

[PK][Id]
[UserId]
[TaskType]
[CreatedDate]
[CompletedDate]

其他三个表格如下：

打印：

[PK][Id]
[TaskId]
[TaskItemId]
[Scnumber]
[Address]
[City]
[Province]
[PostalCode]
[Country]

取消：

[PK][Id]
[TaskId]
[TaskItemId]
[Scnumber]

如果我在SQL中做任何事情都不会有任何问题，但在EntityFramework中，当我尝试添加一个与之关联的打印项目的任务时，我的数据库上下文出现了问题。

public partial class Tasks
{
   public Tasks()
   {
      Items = new HashSet<ITaskItem>();
   }

   public long Id { get; set; }
   public string UserId { get; set; }
   public byte TaskType { get; set; }
   public DateTime CreatedDate { get; set; }
   public DateTime? CompletedDate { get; set; }

   public ICollection<ITaskItem> Items { get; set; }
}

public interface ITaskItem { }

public partial class Cancelations : ITaskItem
{
   public long Id { get; set; }
   public long TaskId { get; set; }
   public string TaskItemId { get; set; }
   public long Scnumber { get; set; }

   public Tasks Task { get; set; }
}

public partial class Print : ITaskItem
{
   public long Id { get; set; }
   public long TaskId { get; set; }
   public string TaskItemId { get; set; }
   public long Scnumber { get; set; }
   public string Address { get; set; }
   public string City { get; set; }
   public string Province { get; set; }
   public string PostalCode { get; set; }
   public string Country { get; set; }

   public Tasks Task { get; set; }
}

所以在我的数据库上下文中，当我构建取消和打印时，当我指定关系时我明确地转换为正确的类型，但是我似乎没有工作和而是转换为错误的类型。在我尝试使用打印项创建任务的情况下，我收到了一个转换错误，但是当我添加取消项时，没有问题。我无法弄清楚为什么会这样。

public partial class DemoDbContext : DbContext
{
   public virtual DbSet<Cancelations> Cancelations { get; set; }
   public virtual DbSet<Print> Print { get; set; }
   public virtual DbSet<Tasks> Tasks { get; set; }

   protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
   {
      if (!optionsBuilder.IsConfigured)
      {
            optionsBuilder.UseSqlServer(@"connection string here");
      }
   }

   protected override void OnModelCreating(ModelBuilder modelBuilder)
   {

      modelBuilder.Entity<Print>(entity =>
      {
            entity.ToTable("Print", "cdi");

            entity.HasIndex(e => e.TaskItemId)
               .HasName("UQ_Print_TaskItemId")
               .IsUnique();

            entity.Property(e => e.Address).HasMaxLength(150);

            entity.Property(e => e.City).HasMaxLength(75);

            entity.Property(e => e.Country).HasColumnType("char(2)");

            entity.Property(e => e.PostalCode).HasMaxLength(15);

            entity.Property(e => e.ProcessedDate)
               .HasColumnType("datetime")
               .HasDefaultValueSql("(getdate())");

            entity.Property(e => e.Province).HasMaxLength(5);

            entity.Property(e => e.TaskItemId)
               .IsRequired()
               .HasColumnType("nchar(39)")
               .HasDefaultValueSql("(concat('P-',newid()))");

            entity.HasOne(d => d.Task)
               .WithMany(p => ((ICollection<Print>)p.Items))
               .HasForeignKey(d => d.TaskId)
               .HasConstraintName("FK_Print_Tasks");
      });

      modelBuilder.Entity<Cancelations>(entity =>
      {
            entity.ToTable("Cancelations", "cdi");

            entity.HasIndex(e => e.TaskItemId)
               .HasName("UQ_Cancelations_TaskItemId")
               .IsUnique();

            entity.Property(e => e.ProcessedDate)
               .HasColumnType("datetime")
               .HasDefaultValueSql("(getdate())");

            entity.Property(e => e.TaskItemId)
               .IsRequired()
               .HasColumnType("nchar(39)")
               .HasDefaultValueSql("(concat('C-',newid()))");

            entity.HasOne(d => d.Task)
               .WithMany(p => ((ICollection<Cancelations>)p.Items))
               .HasForeignKey(d => d.TaskId)
               .HasConstraintName("FK_Cancelations_Tasks");
      });

      modelBuilder.Entity<Tasks>(entity =>
      {
            entity.ToTable("Tasks", "cdi");

            entity.Property(e => e.CompletedDate).HasColumnType("datetime");

            entity.Property(e => e.CreatedDate).HasColumnType("datetime");

            entity.Property(e => e.UserId)
               .IsRequired()
               .HasMaxLength(36);
      });
   }
}

当我尝试执行以下操作时出现此错误：

var context = new DemoDbContext（）;

var task = new Tasks
{
   CreatedDate = DateTime.Now
};

var items = new List<ITaskItem>
{
   new Print
   {
   Scnumber = 0000000001,
   Address = "123 Demo St",
   City = "Toronto",
   Province = "ON",
   PostalCode = "H0H0H0",
   Country = "CA",
   ProcessedDate = DateTime.Now

   },
   new Print
   {
   Scnumber = 0000000001,
   Address = "123 Demo St",
   City = "Toronto",
   Province = "ON",
   PostalCode = "H0H0H0",
   Country = "CA",
   ProcessedDate = DateTime.Now

   },
};

task.Items = items; //cancellations;
task.UserId = "moo cow";
task.TaskType = 1;

try
{
      context.Tasks.Add(task);
      context.SaveChanges();
} catch(Exception ex)
{
      Console.WriteLine(ex);
}

Unable to cast object of type 'temp.Models.Print' to type 'temp.Models.Cancelations'.

Fluent绑定无法使用EntityFramework Core转换为模型

0 个答案: