I've to perform on some collection and return ranking based on some logic I wish to optimize this working code since I think it can be bettered (maybe using Tasks?)

Here's my code and extension method that performs the search

public class Counterpart
{
    public int Id { get; set; }

    public string Code { get; set; }

    public string Description { get; set; }

    public IEnumerable<Alias> Aliases { get; set; }

    public override bool Equals(object obj)
    {
        Counterpart obj2 = obj as Counterpart;
        if (obj2 == null) return false;
        return Id == obj2.Id;
    }
}

public class Alias
{
    public int? Type { get; set; }

    public string Description { get; set; }
}

internal class CounterPartRanking
{
    public int Rank { get; set; }

    public Counterpart CounterPart { get; set; }
}

public static class CounterpartExtensions
{
    public static IEnumerable<Counterpart> SearchWithRank(this IEnumerable<Counterpart> source, string pattern)
    {
        var items1 = source.Where(x => x.Code == pattern);
        var items2 = source.Where(x => x.Code.StartsWith(pattern));
        var items3 = source.Where(x => x.Code.Contains(pattern));
        var items4 = source.Where(x => x.Description.Contains(pattern));
        var items5 = source.Where(x => x.Aliases != null && x.Aliases.Any(y => y.Description == pattern));
        var items6 = source.Where(x => x.Aliases != null && x.Aliases.Any(y => y.Description.StartsWith(pattern)));
        var items7 = source.Where(x => x.Aliases != null && x.Aliases.Any(y => y.Description.Contains(pattern)));

        Stopwatch sw = Stopwatch.StartNew();
        var rankedItems = new List<CounterPartRanking>();


        if (items1.Any())
            rankedItems.AddRange(items1.Select(x => new CounterPartRanking { Rank = 1, CounterPart = x }));
        if (items2.Any())
            rankedItems.AddRange(items2.Select(x => new CounterPartRanking { Rank = 2, CounterPart = x }));
        if (items3.Any())
            rankedItems.AddRange(items3.Select(x => new CounterPartRanking { Rank = 3, CounterPart = x }));
        if (items4.Any())
            rankedItems.AddRange(items4.Select(x => new CounterPartRanking { Rank = 4, CounterPart = x }));
        if (items5.Any())
            rankedItems.AddRange(items5.Select(x => new CounterPartRanking { Rank = 5, CounterPart = x }));
        if (items6.Any())
            rankedItems.AddRange(items6.Select(x => new CounterPartRanking { Rank = 6, CounterPart = x }));
        if (items7.Any())
            rankedItems.AddRange(items7.Select(x => new CounterPartRanking { Rank = 7, CounterPart = x }));

        sw.Stop();

        Debug.WriteLine("Time elapsed {0} for {1}", sw.Elapsed, pattern);
        var items = rankedItems.OrderBy(x => x.Rank).Select(x => x.CounterPart);
        var distinct = items.Distinct();

        return distinct;
    }
}

Any suggestions? Thanks