I am trying to create a custom attribute that uses umbraco dictionary value.

I do not know how to get the UmbracoHelper instance as I don't thunk a custom attribute supports dependency injection.

Any thoughts how to get UmbracoHelper in other way than DI?

This is what I have:

[AttributeUsage(AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]
public sealed class UmbracoDisplayAttribute : DisplayNameAttribute
{
    private readonly UmbracoHelper _umbracoHelper; // <- this value is missing

    // This is a positional argument
    public UmbracoDisplayAttribute(string dictionaryKey)
        : base(dictionaryKey)
    {
    }

    public override string DisplayName
    {
        get
        {
            return _umbracoHelper != null ? _umbracoHelper.GetDictionaryValue(base.DisplayName) : string.Empty;
        }
    }
}