Predicate<T> matches me

Jonas Elfström — Thu, 29 Jan 2009 21:29:00 +0100

I really like the Predicate(T) delegates that were added to the generic collections and lists in .NET 2.0. With the later addition of lambda expressions came cleanliness and readability.

Today we faced a quite simple problem that were made even simpler by the dear predicates. We had a kind of event log and wanted to filter it client side (Windows Forms) using a list of criterias. We began by implementing to filter by a number of categories. It ended up being only one row (in Visual Studio, for obvious reasons not here):

private List<Events> FilterEventsByCategory(List<Events> events,
                                        List<Category> categories) 
{
  return events.FindAll(event => 
      categories.Exists(category => category.CategoryId==event.CategoryId)); 
}

Neat!

"Predicate matches me" by jonelf

Fri, 30 Jan 2009 10:34:37 +0100

See http://stackoverflow.com/questions/493893/many-many-to-many-filters for a many many-to-many filter solution.

Alice, Bob and Mallory: Predicate matches me

Predicate<T> matches me

"Predicate matches me" by jonelf