What is the purpose of "()=>" [duplicate]

Question

I haven't really come across this syntax during my Programming classes in Uni before and I'm curious as to what it means.

The only times I've had to implement it was:

1. When I had to create a BackgroundWorker that had to be added to the ProgressChanged event

   Invoke((MethodInvoker)(() => updatePing((int) e.UserState)));

2. When researching tutorials on using the Caliburn.Micro MVVM framework

   NotifyOfPropertyChange(() => Count);

I have tried searching around on what this notation means but the special characters it uses seem to mess with google search and I have no idea what it is called.

Answer 1

The => is syntax for a lambda expression.

The () signifies that there are no parameters - if there were parameters and the types could be inferred from context, they could be specified as something like this:

(x, y) => x + y

Or specifying the types explicitly

(int x, string y) => x + y.Length

If there's only one parameter and its type can be inferred, you don't need the brackets:

x => x.Length