C# – Linq2sql inheritance cast

clinq-to-sql

I'm usign inheritance in linq2sql and have entites Supplier and Buyer that inherits from Client. I need to be able "upgrade" a Buyer to a Supplier.

I've tried:

        Client client = ClientMethods.ValidateId<Client>(clientId);
        client.ClientTypeId = ClientMethods.CLIENT_TYPE_SUPPLIER;
        db.SubmitChanges();

But get "Not allowed: Inheritance discriminator change from '1' to '2' would change type from 'Buyer' to 'Supplier'."

The only solution I can find is to do this without linq2sql and write a SP??

Best Answer

I am wondering why you even have the two different sub classes if it is a natural situation that you want to change from one type to the other. I think that you should refactor what you have and make the buyer and supplier one entity. Then if you have behavior that should be different based on whether or not the client is a buyer or supplier I would extract that into a seperate object which you can set or add to the client.

Related Solutions

C# – How to cast int to enum

From an int:

YourEnum foo = (YourEnum)yourInt;

From a string:

YourEnum foo = (YourEnum) Enum.Parse(typeof(YourEnum), yourString);

// The foo.ToString().Contains(",") check is necessary for enumerations marked with an [Flags] attribute
if (!Enum.IsDefined(typeof(YourEnum), foo) && !foo.ToString().Contains(","))
{
    throw new InvalidOperationException($"{yourString} is not an underlying value of the YourEnum enumeration.")
}

Update:

From number you can also

YourEnum foo = (YourEnum)Enum.ToObject(typeof(YourEnum) , yourInt);

C# – Multiple Inheritance in C#

Consider just using composition instead of trying to simulate Multiple Inheritance. You can use Interfaces to define what classes make up the composition, eg: ISteerable implies a property of type SteeringWheel, IBrakable implies a property of type BrakePedal, etc.

Once you've done that, you could use the Extension Methods feature added to C# 3.0 to further simplify calling methods on those implied properties, eg:

public interface ISteerable { SteeringWheel wheel { get; set; } }

public interface IBrakable { BrakePedal brake { get; set; } }

public class Vehicle : ISteerable, IBrakable
{
    public SteeringWheel wheel { get; set; }

    public BrakePedal brake { get; set; }

    public Vehicle() { wheel = new SteeringWheel(); brake = new BrakePedal(); }
}

public static class SteeringExtensions
{
    public static void SteerLeft(this ISteerable vehicle)
    {
        vehicle.wheel.SteerLeft();
    }
}

public static class BrakeExtensions
{
    public static void Stop(this IBrakable vehicle)
    {
        vehicle.brake.ApplyUntilStop();
    }
}


public class Main
{
    Vehicle myCar = new Vehicle();

    public void main()
    {
        myCar.SteerLeft();
        myCar.Stop();
    }
}

Best Answer

Related Solutions

C# – How to cast int to enum

C# – Multiple Inheritance in C#

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