How do I map a column to a complex type in EF4 using code first CTP5? [closed]

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Closed 7 years ago.

Having bumped into the of the lack of enum property support in Entity Framework 4 I discovered this article which describes a workaround:

Entity Framework 4.0 Beta 1 – POCO Enum support?

How do I express the mapping of a database column to the OrderStatusWrapper (as described in the article) in code rather than in the designer?

Update:

Based on the answers provided, I hadn't realised that I needed to replace the OrderStatus enum with the OrderStatusWrapper type, i.e.

Instead of:

public class Order 
{
    public OrderStatus Status { get; set; }
}

I should be using:

public class Order 
{
    public OrderStatusWrapper Status { get; set; }
}

This gets me a bit further, however upon executing the following code:

// OrderContext class defined elsewhere as:
// public class OrderContext : DbContext
// {
//   public DbSet<Order> Orders { get; set; }
// }
using(OrderContext ctx = new OrderContext())
{
    Order order = new Order { Status = OrderStatus.Created; }
    ctx.Orders.Add(order);
    ctx.SaveChanges();
} 

The following exception is raised (trimmed for brevity):

System.Data.SqlClient.SqlException
            Message=Invalid column name 'Value'.

The database column is named Status. I tried decorating the Status property with:

[Column("Status")]

then

[Column("Status"), TypeName("OrderStatus")]

and

[Column("Status"), TypeName("OrderStatusWrapper")]

But this doesn't resolve this exception.

I also tried removing the Column attribute and doing this:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Order>()
      .Property(p => p.OrderStatus)
      .HasColumnName("OrderStatus");
}

But I get the following compile error:

Error 1 The type 'ConsoleApplication1.OrderStatusWrapper' must be a non-nullable value type in order to use it as parameter 'T' in the generic type or method 'System.Data.Entity.ModelConfiguration.Configuration.Types.StructuralTypeConfiguration.Property(System.Linq.Expressions.Expression>)' [snipped path]

回答1:

in the context file write this:

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.ComplexType<OrderStatusWrapper>();
            base.OnModelCreating(modelBuilder);
        }

it should work.

EDIT:

public class Order
{
     public...
     ...
     public OrderStatusWrapper OrderStatus { get; set; }
}

public ActionResult Index()
{
    var result = _context.Orders.Where(o => o.OrderStatus == OrderStatus.ReadyForShipping);

    _context.Orders.Add(new Order{ ..., OrderStatus = OrderStatus.Shipped });

    ...;
}

if you did as that example shows along with that small piece of code i showed the above (until EDIT:) should work as expected.

EDIT nr2: If our wrapper looks like this:

public class OrderStatusWrapper
{
    private OrderStatus _status;

    public int Value
    {
        get { return (int)_status; }
        set { _status = (OrderStatus)value; }
    }
    public OrderStatus EnumValue
    {
        get { return _status; }
        set { _status = value; }
    }
    public static implicit operator
         OrderStatusWrapper(OrderStatus status)
    {
        return new OrderStatusWrapper { EnumValue = status };
    }

    public static implicit operator
        OrderStatus(OrderStatusWrapper statusWrapper)
   {
       if (statusWrapper == null) return OrderStatus.OrderCreated;
       else return statusWrapper.EnumValue;
   }
}

The database takes the name of the property Value, so if you change that property name to Status, the column in the database would change to Status.

回答2:

The following code is how the mappings looks like in Code First CTP5. In this case Code First will automatically recognize OrderStatusWrapper as a complex type due to a concept called Complex Type Discovery that works based on the Reachability Convention. You don't even need to use ComplexTypeAttribute or the ComplexType<T>() fluent API to explicitly register OrderStatusWrapper as a complex type.

For more info please take a look at this post:
Entity Association Mapping with Code First CTP5: Complex Types

Update:

Due to a bug in CTP5, if you want to have a custom column name for your complex type properties (e.g. [Orders].[Status] for OrderStatusWrapper.Value in DB), then you have to explicitly mark it with [ComplexType]:

public class Order
{
    public int OrderId { get; set; }
    public DateTime CreatedOn { get; set; }               
    public OrderStatusWrapper Status { get; set; }
}    

[ComplexType]
public class OrderStatusWrapper 
{
    private OrderStatus _status;

    [Column(Name="Status")]
    public int Value {
        get { return (int)_status; }
        set { _status = (OrderStatus)value; }
    }
    public OrderStatus EnumValue {
        get { return _status; }
        set { _status = value; }
    }
}

public enum OrderStatus
{
    OrderCreated,
    OrderPayed,
    OrderShipped
}

Since you are working with an existing database, you can optionally switch off metadata table in database as well:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Conventions
                .Remove<System.Data.Entity.Database.IncludeMetadataConvention>();
}

来源：https://stackoverflow.com/questions/4484370/how-do-i-map-a-column-to-a-complex-type-in-ef4-using-code-first-ctp5