linq - How can I do an OrderBy with a dynamic string parameter?

Question

I want to do this:

var orderBy = "Nome, Cognome desc";

var timb = time.Timbratures.Include("Anagrafica_Dipendente")
    .Where(p => p.CodDipendente == 1);

if(orderBy != "")
    timb = timb.OrderBy(orderBy);

Is there an OrderBy overload available that accepts a string parameter?

Answer 1

If you are using plain LINQ-to-objects and don't want to take a dependency on an external library it is not hard to achieve what you want.

The OrderBy() clause accepts a Func<TSource, TKey> that gets a sort key from a source element. You can define the function outside the OrderBy() clause:

Func<Item, Object> orderByFunc = null;

You can then assign it to different values depending on the sort criteria:

if (sortOrder == SortOrder.SortByName)
  orderByFunc = item => item.Name;
else if (sortOrder == SortOrder.SortByRank)
  orderByFunc = item => item.Rank;

Then you can sort:

var sortedItems = items.OrderBy(orderByFunc);

This example assumes that the source type is Item that have properties Name and Rank.

Note that in this example TKey is Object to not constrain the property types that can be sorted on. If the func returns a value type (like Int32) it will get boxed when sorting and that is somewhat inefficient. If you can constrain TKey to a specific value type you can work around this problem.