yikes.cs

public class TextLiteral
{
    [EdifactElement(0)]
    public string Line0 { get; set; }

    [EdifactElement(1, required: false)]
    public string Line1 { get; set; }

    [EdifactElement(2, required: false)]
    public string Line2 { get; set; }

    [EdifactElement(3, required: false)]
    public string Line3 { get; set; }

    [EdifactElement(4, required: false)]
    public string Line4 { get; set; }

    public IEnumerable<string> Lines
    {
        get
        {
            yield return Line0;
            if (Line1 != null) yield return Line1;
            if (Line2 != null) yield return Line2;
            if (Line3 != null) yield return Line3;
            if (Line4 != null) yield return Line4;
        }
    }
}