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honey the codewitch wrote:

But also a little inconsistency never really bothered me that much.

var genericArguments = obj.GetType().GetGenericArguments();
if (genericArguments.Length != 0)
{
    Columns.AddRange(genericArguments[0].GetProperties()
        .Where(p => p.GetCustomAttributes(true).OfType<BrowsableAttribute>().FirstOrDefault()?.Browsable ?? DefaultBrowsableState)
        .Select(p => new ColumnHeader
        {
            Name = p.Name,
            Text = p.GetCustomAttributes(true).OfType<DisplayNameAttribute>().FirstOrDefault()?.DisplayName ?? p.Name,
        });
}

public static class AttributeExtensions
{
    public static TAttribute GetCustomAttribute<TAttribute>(this ICustomAttributeProvider value, bool inherit = true)
        where TAttribute : Attribute
    {
        if (value is null) throw new ArgumentNullException(nameof(value));
        
        object[] attributes = value.GetCustomAttributes(typeof(TAttribute), inherit);
        return attributes.Length == 0 ? null : (TAttribute)attributes[0];
    }
}

var genericArguments = obj.GetType().GetGenericArguments();
if (genericArguments.Length != 0)
{
    Columns.AddRange(genericArguments[0].GetProperties()
        .Where(p => p.GetCustomAttribute<BrowsableAttribute>()?.Browsable ?? DefaultBrowsableState)
        .Select(p => new ColumnHeader
        {
            Name = p.Name,
            Text = p.GetCustomAttribute<DisplayNameAttribute>()?.DisplayName ?? p.Name,
        });
}

Columns
.AddRange(
    obj.GetType()
    .GetGenericArguments()
    .FirstOrDefault()?.GetProperties()

    // need the Elvis operator 
    ?.Where(p =>
    {
        return p.GetCustomAttributes(true)
                .OfType<BrowsableAttribute>()
                .FirstOrDefault()?.Browsable ?? DefaultBrowsableState;
    })

    // need the Elvis operator 
    ?.Select(p =>
    {
        return new ColumnHeader()
        {
            Name = p.Name,
            Text = p.GetCustomAttributes(true)
                    .OfType<DisplayNameAttribute>().FirstOrDefault()?.DisplayName ?? p.Name
        };
    })

    // don't need ToArray(), but need to provide a non-null value for AddRange()
    ?? Array.Empty<ColumnHeader>()
 );

Matthew Dennis wrote:

I find that adding line breaks makes it a lot easier to read

Matthew Dennis wrote:

It is missing some Elvis operators

Type.GetProperties Method (System) | Microsoft Docs[^]:

Returns
An array of PropertyInfo objects representing all public properties of the current Type.
-or-
An empty array of type PropertyInfo, if the current Type does not have public properties.

A()?.Bb()?.C().D()

static Foo A() => null;

public class Foo
{
    public Foo B() => null;
    public Foo C() => null;
    public Foo D() => null;
}

...

Foo result = A()?.B().C().D(); // result == null; no exception thrown.