class Foo {}
class Bar : Foo {}

public static Extension (this Foo foo) {}
public static Extension (this Bar bar) {}

Foo bar = new Bar();
bar.Extension();

        var foo = null as object;
        var bar = (object) null;

namespace ConsoleApp1
{
    public class Foo
    {
    }

    public static class Extensions
    {
        public static void StringExt(this Foo value)
        {
            Console.WriteLine(value);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Foo foo = null;
            Extensions.StringExt(foo);
            foo.StringExt();
        }
    }
}

static void Main(string[] args)
{
    Foo foo = null;
    Extensions.StringExt(null);
    ((Foo)null).StringExt();
}

SeverityFilters = new ObservableCollection<string>(
    new[]
    {
        _initializedSeverityFilter,
        CodeInspectionSeverity.DoNotShow.ToString(),
        CodeInspectionSeverity.Error.ToString(),
        CodeInspectionSeverity.Warning.ToString(),
        CodeInspectionSeverity.Suggestion.ToString(),
        CodeInspectionSeverity.Hint.ToString()
    });

new ObservableCollection<string>(new[]
        {InspectionsUI.ResourceManager.GetString("Your_New_Resource", CultureInfo.CurrentUICulture)}
    .Concat(Enum.GetNames(typeof(CodeInspectionSeverity)).Select(s =>
        InspectionsUI.ResourceManager.GetString("CodeInspectionSeverity_" + s,
            CultureInfo.CurrentUICulture))));

                var indent = currentContent.NthIndexOf('"', 1);
                var whitespace = new string(' ', indent);
                var code = $"{currentContent} & _\r\n{whitespace}\"";

                if ((e.Keys & Keys.Control) != Keys.Control)
                {
                    code = $"{currentContent} & vbNewLine & _\r\n{whitespace}\"";
                }