combining empty/null arrays

I have a page that can pass anywhere from 1 array to 3 arrays.

My current code works but only if each array is populated with items.

    [HttpPost, ValidateInput(false)]
    public ActionResult AddCampaign(string campaignName, string editor1, Int32[]
 productImages, Int32[] lifestyleImages, Int32[] logoImages)
    {

        // Add image list to CampaignImages table
        // Combine image array list into a single array
        var imageList = productImages.Concat(lifestyleImages).Concat(logoImages).ToArray();

        return RedirectToAction("AddCampaign", "Admin");
    }

Each array is the exact same it will only hold an ID of an image. This will work as long as all 3 arrays have something in them. But if one is null it errors out.

What I need is a single array that is a combination of all 3 arrays, productImages, lifestyleImages, logoImages.

Not sure what I am missing.

Jon Skeet
people
quotationmark

Well you're missing the fact that Concat will throw an exception if you pass it a null reference... but it's easy enough to fix. Either write an extension method like this:

public static IEnumerable<T> NullToEmpty<T>(this IEnumerable<T> src)
{
    return src ?? Enumerable.Empty<T>();
}

And call it as:

var imageList = productImages.NullToEmpty()
                             .Concat(lifestyleImages.NullToEmpty())
                             .Concat(logoImages.NullToEmpty())
                             .ToArray();

... or just use the null-coalescing operator directly:

var empty = Enumerable.Empty<int>();

var imageList = (productImages ?? empty).Concat(lifeStyleImages ?? empty)
                                        .Concat(logoImages ?? empty)
                                        .ToArray();

people

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