Lambda expressions

[TexMurphy01]

Hi there. This is a general C# question about lambda expressions. I've read the chapter in my book about it (Schildt's C# 4.0) and there is one use of it that I run into online that the book does not cover and that I do not understand.

Here are a couple of examples:

EnqueueCallback(() => Assert.AreNotEqual(viewModel.Products, null,
"Expected non-null products list."));

Delete = new DeleteCommand(
Service,
()=>CanDelete,
contact =>
{
CurrentContact = null;
Service.GetContacts(_PopulateContacts);
});

So the bit I don't understand is the notation with the empty brackets ( ()=> ). What is this all about? Can someone explain it please?

[dglienna]

Delete is the LAMBDA which contains the actual code that fires when the ASSERT is TRUE (not NULL). It won't delete a record that isn't there

[TexMurphy01]

I guess I didn't make myself clear with what I wished to know. Those examples aren't what I'm interested in, it's specifically the '()=>'. I don't really get what it is.

[ThermoSight]

The => operator indicates to the compiler that this is a lambda expression.

The empty parentheses to the left of the operator indicates that this lambda expression takes no arguments, while everything to the right of the operator is the body of the expression.

The body of the expression could be a call to a named function or it could be a bracketed series of one or more statements, to wit: {x++; return x * x;}

incidentally, I think that the braces {} may be omitted if there is only a single statment in the body, for instance () => parser.ParseThis(HTML_string); (although for the life of me, I can't imagine why anyone would use a single-statement lambda expression - perhaps as an argument to a function or to subscribe to an event - like a delegate).

[TexMurphy01]

Hmm I see. Nice answer - thanks a lot.