The C# specification explicitly states (IIRC) that if you have two anonymous functions (anonymous methods or lambda expressions) it may or may not create equal delegates from that code. (Two delegates are equal if they have equal targets and refer to the same methods.) To be sure, you’d need to remember the delegate instance you … Read more
As Brannon says, it’s OrderByDescending and ThenByDescending: var query = from person in people orderby person.Name descending, person.Age descending select person.Name; is equivalent to: var query = people.OrderByDescending(person => person.Name) .ThenByDescending(person => person.Age) .Select(person => person.Name);
UPDATE 2018: C++20 will come with templated and conceptualized lambdas. The feature has already been integrated into the standard draft. UPDATE 2014: C++14 has been released this year and now provides Polymorphic lambdas with the same syntax as in this example. Some major compilers already implement it. At it stands (in C++11), sadly no. Polymorphic … Read more
Try the following var targetList = origList .Select(x => new TargetType() { SomeValue = x.SomeValue }) .ToList(); This is using a combination of Lambdas and LINQ to achieve the solution. The Select function is a projection style method which will apply the passed in delegate (or lambda in this case) to every value in the … Read more
Use the SelectMany extension method list = listOfList.SelectMany(x => x).ToList();
To mark a lambda async, simply prepend async before its argument list: // Add a command to delete the current Group contextMenu.Commands.Add(new UICommand(“Delete this Group”, async (contextMenuCmd) => { SQLiteUtils slu = new SQLiteUtils(); await slu.DeleteGroupAsync(groupName); }));
The code essentially calls an empty lambda. Let’s start from the beginning: [](){} is an empty lambda expression. Then, in C and C++, you can wrap expressions in parens and they behave exactly the same† as if written without them, so that’s what the first pair of parens around the lambda does. We’re now at … Read more
Java 9 Optional.stream has been added to JDK 9. This enables you to do the following, without the need of any helper method: Optional<Other> result = things.stream() .map(this::resolve) .flatMap(Optional::stream) .findFirst(); Java 8 Yes, this was a small hole in the API, in that it’s somewhat inconvenient to turn an Optional<T> into a zero-or-one length Stream<T>. … Read more
The recommendation in PEP-8 you are running into is: Always use a def statement instead of an assignment statement that binds a lambda expression directly to a name. Yes: def f(x): return 2*x No: f = lambda x: 2*x The first form means that the name of the resulting function object is specifically ‘f’ instead … Read more
This can be done as list.Sort( (emp1,emp2)=>emp1.FirstName.CompareTo(emp2.FirstName) ); The .NET framework is casting the lambda (emp1,emp2)=>int as a Comparer<Employee>. This has the advantage of being strongly typed. If you need the descending/reverse order invert the parameters. list.Sort( (emp1,emp2)=>emp2.FirstName.CompareTo(emp1.FirstName) );