IList - LINQ to filter and order by

Question

I have the following test code to search a generic list:

public void DoSearch(string searchTerm)
{

IList<MyEntity> entities = GetCollectionOfEntities();

IList<MyEntity> results = entities.Where(d => d.Description.Contains(searchTerm)).ToList();

}

I want to pass an order by parameter (which would be a property of MyEntity) and of course order my results based on that. I understand LINQ uses OrderBy but do not understand how to order by a property of MyEntity.

Solution

You just use a Func<TSource,TKey> to specify the property that you want to order by:

DoSearch("foo", e => e.SomeProperty);

// ...

public void DoSearch<TKey>(string searchTerm, Func<MyEntity, TKey> orderBy)
{
    IList<MyEntity> entities = GetCollectionOfEntities();

    IList<MyEntity> results = entities
                              .Where(e => e.Description.Contains(searchTerm))
                              .OrderBy(orderBy)
                              .ToList();

    // etc
}

Comments

[youwhut]

Okay this is a good start but how would I go about passing this as a parameter so that my method signature would be public void DoSearch(string searchTerm, orderby)...?

[Benjamin Podszun]

Not at all or using Reflection (which is slow and probably not useful in general). The Func<> way is really the best way to go here imo. +1

[youwhut]

Excellent. Cheers for the help.

[LukeH]

@youwhut: You'd need to pass the Func<S,K> into the method itself. I've updated the answer to demonstrate.

[Jéf Bueno]

@LukeH what's the reason to use TKey?