C# remove null values from object array

Question

I got an array of a specific object. Lets say the object Car. At some point in my code I need to remove all Car-objects from this array that do not fulfill the requirements I stated. This leaves null values in the array.

public class Car{
    public string type { get; set; }

    public Car(string ntype){
        this.type = ntype;
    }
}

Car[] cars = new Car[]{ new Car("Mercedes"), new Car("BMW"), new Car("Opel");

//This should function remove all cars from the array where type is BMW.
cars = removeAllBMWs(cars);

//Now Cars has become this.
Cars[0] -> Car.type = Mercedes
Cars[1] -> null
Cars[2] -> Car.type = Opel

//I want it to become this.
Cars[0] -> Car.type = Mercedes
Cars[1] -> Car.type = Opel

Of course my real code is far more complex than this, but the base idea is the same. My question that I have is: How can I remove the empty values from this array?

I found countless solutions for a string array, but none for an object array.

"I found countless solutions for a string array, but none for an object array" - pretty sure they'll work for Car as well as they work for string... — Rawling
– Rawling, Commented Jan 28, 2015 at 13:34
Why not just use a list instead of an array? then you wont have any nulls — Sayse
– Sayse, Commented Jan 28, 2015 at 13:35
@kpp - You seem to have written the removeAllBMWs method yourself (or your team has) so I'd say just make that return a list since you are already modifying the array — Sayse
– Sayse, Commented Jan 28, 2015 at 13:41

JLRishe · Accepted Answer · 2015-01-28 13:42:26Z

51

The following will create a new array with all the null values excluded (which seems to be what you actually want?):

Cars = Cars.Where(c => c != null).ToArray();

Better yet, define your RemoveAllBMWs method to omit the BMWs in the first place instead of setting them to null:

internal static Car[] RemoveAllBMWs(IEnumerable<Car> cars)
{
    return cars.Where(c => c != null && c.Type != "BMW").ToArray();
}

edited Jan 28, 2015 at 13:42

answered Jan 28, 2015 at 13:33

JLRishe

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3 Comments

Tim Schmelter Over a year ago

But the question is why he first uses a method removeAllBMWs which modifies the array in a way that it assigns null to every BMW. You could do both in one with cars.Where(c => c.type == "BMW").ToArray()

kpp Over a year ago

@TimSchmelter, this is a simplified version. I do not personally instantiate the array I receive it via a webservice from another application. Not all values in this array are useful though.

JLRishe Over a year ago

@TimSchmelter True, though I think you meant !=, not ==. I've added an addendum.

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