Question

I have two functions whose underlying logic is the same but in one case it sets one property value on a class and in another case it sets a different one. How can I rewrite the following two functions to abstract away as much of the algorithm as possible so that I can make changes in logic in a single place?

SetBillingAddress

private void SetBillingAddress(OrderAddress newBillingAddress)
{
    BasketHelper basketHelper = new BasketHelper(SiteConstants.BasketName);
    OrderAddress oldBillingAddress = basketHelper.Basket.Addresses[basketHelper.BillingAddressID];

    bool NewBillingAddressIsNotOldBillingAddress = ((oldBillingAddress == null) || (newBillingAddress.OrderAddressId != oldBillingAddress.OrderAddressId));
    bool BillingAddressHasBeenPreviouslySet = (oldBillingAddress != null);
    bool BillingAddressIsNotSameAsShippingAddress = (basketHelper.ShippingAddressID != basketHelper.BillingAddressID);
    bool NewBillingAddressIsNotShippingAddress = (newBillingAddress.OrderAddressId != basketHelper.ShippingAddressID);

    if (NewBillingAddressIsNotOldBillingAddress && BillingAddressHasBeenPreviouslySet && BillingAddressIsNotSameAsShippingAddress)
    {
        basketHelper.Basket.Addresses.Remove(oldBillingAddress);
    }

    if (NewBillingAddressIsNotOldBillingAddress && NewBillingAddressIsNotShippingAddress)
    {
        basketHelper.Basket.Addresses.Add(newBillingAddress);
    }

    basketHelper.BillingAddressID = newBillingAddress.OrderAddressId;
    basketHelper.Basket.Save();
}

And here is the second one:

SetShippingAddress

private void SetShippingAddress(OrderAddress newShippingAddress)
{
    BasketHelper basketHelper = new BasketHelper(SiteConstants.BasketName);
    OrderAddress oldShippingAddress = basketHelper.Basket.Addresses[basketHelper.ShippingAddressID];

    bool NewShippingAddressIsNotOldShippingAddress = ((oldShippingAddress == null) || (newShippingAddress.OrderAddressId != oldShippingAddress.OrderAddressId));
    bool ShippingAddressHasBeenPreviouslySet = (oldShippingAddress != null);
    bool ShippingAddressIsNotSameAsBillingAddress = (basketHelper.ShippingAddressID != basketHelper.BillingAddressID);
    bool NewShippingAddressIsNotBillingAddress = (newShippingAddress.OrderAddressId != basketHelper.BillingAddressID);

    if (NewShippingAddressIsNotOldShippingAddress && ShippingAddressHasBeenPreviouslySet && ShippingAddressIsNotSameAsBillingAddress)
    {
        basketHelper.Basket.Addresses.Remove(oldShippingAddress);
    }

    if (NewShippingAddressIsNotOldShippingAddress && NewShippingAddressIsNotBillingAddress)
    {
        basketHelper.Basket.Addresses.Add(newShippingAddress);
    }

    basketHelper.ShippingAddressID = newShippingAddress.OrderAddressId;
    basketHelper.Basket.Save();
}

My initial thought was that if I could pass a class’s property by refernce then I could rewrite the previous functions into something like

private void SetPurchaseOrderAddress(OrderAddress newAddress, ref String CurrentChangingAddressIDProperty)

and then call this function and pass in either basketHelper.BillingAddressID or basketHelper.ShippingAddressID as CurrentChangingAddressIDProperty but since I can’t pass C# properties by reference I am not sure what to do with this code to be able to reuse the logic in both places.

Thanks for any insight you can give me.

Answer 1

You can pass lambda expressions:

private void SetPurchaseOrderAddress(OrderAddress newAddress, Func<string> addressIDGetter, Action<string> addressIDSetter) 

Call it like this:

SetPurchaseOrderAddress(newAddress, () => basketHelper.BillingAddressID, a => basketHelper.BillingAddressID = a);