Sorting by patients' name or birth

Question

Is there a way to write this simpler?

if(criteria.SortBy =="name")
{
    if (criteria.SortDirection == "ascending")
    {
        physicians.Sort((x, y) => string.Compare(x.Name, y.Name));
    }
    else
    {
        physicians.Sort((x, y) => string.Compare(y.Name,x.Name ));

    }
}

if (criteria.SortBy == "birth")
{
    if (criteria.SortDirection == "ascending")
    {
        physicians.Sort(new Comparison<Physician>((x, y) => DateTime.Compare(x.DateOfBirth ?? DateTime.MinValue,y.DateOfBirth ?? DateTime.MinValue)));
    }
    else
    {
        physicians.Sort(new Comparison<Physician>((x, y) => DateTime.Compare(y.DateOfBirth ?? DateTime.MinValue, x.DateOfBirth ?? DateTime.MinValue)));

    }
}

Answer 1

You can use the ComparerExtensions library to help you create comparers more easily.

With it, your code could look something like:

IComparer<Physician> comparer = null;

if (criteria.SortBy == "name")
{
    comparer = KeyComparer<Physician>.OrderBy(x => x.Name);
}
else if (criteria.SortBy == "birth")
{
    comparer = KeyComparer<Physician>.OrderBy(x => x.DateOfBirth);
}

if (comparer != null)
{
    if (criteria.SortDirection != "ascending")
    {
        comparer = comparer.Reversed();
    }

    physicians.Sort(comparer);
}

Answer 2

You could use a pattern like this

var factor = 
    criteria.SortDirection == "ascending" ? 1 : -1;

if(criteria.SortBy =="name")
    physicians.Sort((x, y) => string.Compare(x.Name, y.Name) * factor);

UPDATE: Based on CodesInChaos' comment. If the magnitude of the Compare result could be at the extremes, Math.Sign can be used to normalize the result.

var factor = 
    criteria.SortDirection == "ascending" ? 1 : -1;

if(criteria.SortBy =="name")
    physicians.Sort((x, y) => Math.Sign(string.Compare(x.Name, y.Name)) * factor);