Can I refactor these functions into one generic function?

Question

I have a dozen classes that inherit from the same baseclass. For each class, I want to change the state when a property updates, so I have a function called UpdateProperty(oldValue, newValue). I'm looking for a way to make these generic, so when I add a new class, I don't have to add a new function. This is what I have:

    public TicketType UpdateProperty(TicketType oldValue, TicketType newValue)
    {
        if (oldValue != newValue && ObjectState != ObjectState.New && ObjectState != ObjectState.Deleted)
        {
            ObjectState = ObjectState.Changed;
        }
        return newValue;
    }

    public Layout UpdateProperty(Layout oldValue, Layout newValue)
    {
        if (oldValue != newValue && ObjectState != ObjectState.New && ObjectState != ObjectState.Deleted)
        {
            ObjectState = ObjectState.Changed;
        }
        return newValue;
    }

    public Division UpdateProperty(Division oldValue, Division newValue)
    {
        if (oldValue != newValue && ObjectState != ObjectState.New && ObjectState != ObjectState.Deleted)
        {
            ObjectState = ObjectState.Changed;
        }
        return newValue;
    }

    public MasterDataList UpdateProperty(MasterDataList oldValue, MasterDataList newValue)
    {
        if (oldValue != newValue && ObjectState != ObjectState.New && ObjectState != ObjectState.Deleted)
        {
            ObjectState = ObjectState.Changed;
        }
        return newValue;
    }

    public MasterDataListItem UpdateProperty(MasterDataListItem oldValue, MasterDataListItem newValue)
    {
        if (oldValue != newValue && ObjectState != ObjectState.New && ObjectState != ObjectState.Deleted)
        {
            ObjectState = ObjectState.Changed;
        }
        return newValue;
    }


    public Ticket UpdateProperty(Ticket oldValue, Ticket newValue)
    {
        if (oldValue != newValue && ObjectState != ObjectState.New && ObjectState != ObjectState.Deleted)
        {
            ObjectState = ObjectState.Changed;
        }
        return newValue;
    }

As you can see, they all do the same. Could someone point me in the right direction?

Also see https://dotnetfiddle.net/xXgRuv

I modified your fiddle with my suggested code dotnetfiddle.net/Edi9xo — Sir Rufo
– Sir Rufo, Commented Dec 13, 2017 at 11:17

Patrick Hofman · Accepted Answer · 2017-12-13 11:26:40Z

2

Yes, but you have to make a generic method. You can put that in a base class if you need to:

public T UpdateProperty<T>(T oldValue, T newValue)
{
    if (!object.Equals(oldValue, newValue) && this.ObjectState != ObjectState.New && this.ObjectState != ObjectState.Deleted)
    {
        this.ObjectState = ObjectState.Changed;
    }

    return newValue;
}

edited Dec 13, 2017 at 11:26

answered Dec 13, 2017 at 10:04

Patrick Hofman

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10 Comments

Sir Rufo Over a year ago

Why do you need a „generic base class“?

Patrick Hofman Over a year ago

I meant that the code inside should be general / generic, not like "generics in c#" @SirRufo. Thanks for the hint.

Sir Rufo Over a year ago

Why does T needs to implement IObjectState?

Patrick Hofman Over a year ago

It seemed to me OP was assigning that value to either oldValue.ObjectState or newValue.ObjectState, like in your answer. @SirRufo

Sir Rufo Over a year ago

I cannot see that in his or your code. Noone is using the ObjectState from newValue or oldValue. The base class has a property ObjectState and that is set

|

Sir Rufo · Accepted Answer · 2017-12-13 10:13:53Z

0

I would not only set the ObjectState, but also the property value inside the method.

Place the method inside the base class.

public abstract class BaseClass
{
    public ObjectState ObjectState { get; private set; }

    protected bool Set<T>( ref T field, T value )
    {
        if Equals( field, value ) return false;
        field = value;
        if ( ObjectState == ObjectState.Unchanged )
          ObjectState = ObjectState.Changed;
        return true;
    }
}

and in your inherited class

public class Foo : BaseClass
{
    private TicketType _ticketType;
    public TicketType TicketType 
    {
        get => _ticketType; 
        set => Set( ref _ticketType, value );
    }
}

answered Dec 13, 2017 at 10:13

Sir Rufo

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1 Comment

smvdbrink Over a year ago

When I change this, it tells me it cannot convert type bool to type TicketType.

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