Directory.GetFiles - how to get rid of the warning Possible null reference argument for parameter 'value'?

Question

Possible null reference argument for parameter 'value' in 'bool string.Contains(string value)'

the warning is on this line on the existing

var link = Links.FirstOrDefault(linkItem => linkItem?.Contains(existing) ?? false);

the code

public void PrepareLinks()
{
    LinksAndFileNames.Clear();
    Links.Clear();

    GenerateRadarLinks();

    // Exclude links for files that already exist in the folder
    foreach (var existing in Directory.GetFiles(Folder, "*.png").Select(Path.GetFileNameWithoutExtension))
    {
        var link = Links.FirstOrDefault(linkItem => linkItem?.Contains(existing) ?? false);
        if (link != null)
        {
            Links.Remove(link);
        }
    }
}

Answer 1

Path.GetFileNameWithoutExtension returns a string?. Such a value could contain a null (even though realistically it's not going to).

You could just say "ignore it" with the ! postfix operator

var link = Links.FirstOrDefault(linkItem => linkItem?.Contains(existing!) ?? false);

Or test it

if (existing == null) continue;
var link = Links.FirstOrDefault(linkItem => linkItem?.Contains(existing) ?? false);

You can however improve the efficiency of your method with two things

• Use EnumerateFiles instead of GetFiles, as the latter returns an array.
• Get the index of the list match and remove at that match

---

foreach (var existing in Directory.EnumerateFiles(Folder, "*.png").Select(Path.GetFileNameWithoutExtension))
{
    if (existing == null) continue;
    var index = Links.FindIndex(linkItem => linkItem?.Contains(existing) ?? false);
    if (index != -1)
    {
        Links.RemoveAt(index);
    }
}

If you want to remove all possible matches, you can simply do

Links.RemoveAll(linkItem => linkItem?.Contains(existing) ?? false);