What does () => mean in C#?

Question

I\'ve been reading through the source code for Moq and I came across the following unit test:

Assert.Throws(() => Times         


        

Answer 1

That's the definition of a lambda (anonymous) function. Essentially, it's a way to define a function inline, since Assert.Throws takes a function as an argument and attempts to run it (and then verify that it throws a certain exception).

Essentially, the snippet you have there is a unit test that makes sure Times.AtLeast(0) throws a ArgumentOutOfRangeException. The lambda function is necessary (instead of just trying to call the Times.AtLeast function directly from Assert.Throws) in order to pass the proper argument for the test - in this case 0.

MSDN KB article on the topic here: http://msdn.microsoft.com/en-us/library/bb882516.aspx