How to check for null in nested references

Best practice is to follow Law of Demeter which sounds as: don't talk to strangers. I.e. object should avoid invoking methods of a member object returned by another method. This allows to write less coupled, more maintainable and readable code.

So, avoid using 'train wrecks' like someOrder.Customer.LastOrder.Product.Color, because they completely violate Law of Demeter. It's even hard to understand what business meaning this code has. Why are you getting color of product of some other order, which is not the current one?

Possible way to remove train wreck - push functionality closer to interesting end of wreck. In your case, also consider passing last product to your method, instead of using some order.

You are looking for the null-safe dereferencing operator.

Color color = someOrder?.Customer?.LastOrder?.Product?.Color;

Unfortunately C# doesn't support it. Maybe it will be added later, but there are no plans to do that at the moment.

Related

• Deep null checking, is there a better way?

where you need to achieve this do this.

Usage

Color color = someOrder.ComplexGet(x => x.Customer.LastOrder.Product.Color);

or

Color color = Complex.Get(() => someOrder.Customer.LastOrder.Product.Color);

Helper Class Implementation

public static class Complex
{
    public static T1 ComplexGet<T1, T2>(this T2 root, Func<T2, T1> func)
    {
        return Get(() => func(root));
    }

    public static T Get<T>(Func<T> func)
    {
        try
        {
            return func();
        }
        catch (Exception)
        {
            return default(T);
        }
    }
}