Question

我正在使用这样的枚举类：

public class BillTransactionState
{
    public static readonly BillTransactionState Initialized = new BillTransactionState(1, "Initialized");
    public static readonly BillTransactionState Invoiceable = new BillTransactionState(2, "Invoiceable");
    public static readonly BillTransactionState NoSow = new BillTransactionState(3, "NoSow");
    public static readonly BillTransactionState Invoiced = new BillTransactionState(4, "Invoiced");

    public virtual int Id { get; set; }
    public virtual string Name { get; set; }
}

我还有另一个引用BillTransactionState的类：

public class BillTransactionStateHistory : IEntity<long>
{
    public long Id { get; set; }
    public DateTime EffectiveDate { get; set; }
    public BillTransactionState BillTransactionState { get; set; }
}

在我的webapi中，当我执行以下操作时：

var billTransactionStateHistory = new BillTransactionStateHistory ({
        BillTransaction = BillTransaction .Initialized,
        EffectiveDate = DateTime.Now
      });
_dbContext.BillTransactionStateHistories.AddAsync(billTransactionStateHistory)

我得到一个错误：

BillTransactionState的身份插入无效。

我意识到EF Core试图在BillTransactionState表中插入值为1（对于Id）和'Initliazed'的行。如何阻止EF Core尝试在此枚举类中插入一行。任何对此的帮助将不胜感激。谢谢。

Answer 1

编写您的BillTransactionStateHistory模型类，如下所示：

public class BillTransactionStateHistory : IEntity<long>
{
    public long Id { get; set; }
    public DateTime EffectiveDate { get; set; }
    public int BillTransactionState { get; set; }
}

注意：之后，别忘了相应地更新数据库！

然后使用Web API方法：

var billTransactionStateHistory = new BillTransactionStateHistory ()
{
   BillTransactionState = BillTransactionState.Initialized.Id,
   EffectiveDate = DateTime.Now
};
_dbContext.BillTransactionStateHistories.AddAsync(billTransactionStateHistory)

Answer 2

您可以在官方的EF Core GitHub存储库上看到this的答案。

您的枚举类和实体类将保持不变。您将必须引入ValueConverter或使用PropertyBuilder.HasConverter来提供与BillTransactionState和int之间的映射。

Lambda示例：

// builder is IEntityTypeConfiguration<BillTransactionStateHistory>
builder.Property(e => e.BillTransactionState)
  .HasColumnName("state")
  .HasConversion(state => state.Id, stateId => SomeLookupMethod(stateId));

public BillTransactionState SomeLookupMethod(int id)
{
  // TODO: Lookup transaction state based on id.
}

请注意，EF Core 2.x的问题在于值转换器和lambda不能正确映射到查询表达式。 EF Core 3.x已修复此（related issue）

EF Core Enumeration类抛出异常

2 个答案: