Linq OrderBy against specific values

Question

Is there a way in Linq to do an OrderBy against a set of values (strings in this case) without knowing the order of the values?

Consider this data:

A         


        

Answer 1

Not really efficient for large lists but fairly easy to read:

public class FixedOrderComparer : IComparer
{
    private readonly T[] fixedOrderItems;

    public FixedOrderComparer(params T[] fixedOrderItems)
    {
        this.fixedOrderItems = fixedOrderItems;
    }

    public int Compare(T x, T y)
    {
        var xIndex = Array.IndexOf(fixedOrderItems, x);
        var yIndex = Array.IndexOf(fixedOrderItems, y);
        xIndex = xIndex == -1 ? int.MaxValue : xIndex;
        yIndex = yIndex == -1 ? int.MaxValue : yIndex;
        return xIndex.CompareTo(yIndex);
    }
}

Usage:

var orderedData = data.OrderBy(x => x, new FixedOrderComparer("A", "B", "C"));

Note: Array.IndexOf(....) uses EqualityComparer.Default to find the target index.