Combining multi coloumn failover logic into a single property in Entity Framework 4.1

i am working on a legacy enterprise database that uses multiple columns to retrieve a part number the sql we currently use checks for a part number and if the part number is null then checks for the child part number what would be the best way of combining this logic into a single ef model property (eg Product.PartNumber )

I would like this to be invisible as possible so that only Par开发者_如何学GotNumber is visible externally to the data api

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If you are using code-first approach the only way is to do a projection in custom linq-to-entities query:

var products = context.Products
                      .Select(p => new SomeNonMappedType
                           {
                               Id = p.Id,
                               // All other fields
                               PartNumber = p.PartNumber ?? p.Child.PartNumber // I hope this will work
                           });

If you are using EDMX you can use DefiningQuery or QueryView but whole your new entity will be readonly. More about those in another answer.

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in theory couldnt you do something like this

public class Part
{ 
    public string PartNumber
    {
        get
        {
            return this.PartId ?? this.ChildPartId;
        }  
    }

    internal string PartId { get; set; }
    internal string ChildPartId { get; set; }
}



public class PartsContext : DbContext
{ 
    public DbSet<Part> Parts { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Part>().Ignore(e => e.PartNumber);   
        base.OnModelCreating(modelBuilder);
    }
}

or is this still considered bad