What is the outcome of "() => true"

I'm reviewing another person's code and can't ask him... What does t开发者_开发知识库hat line of C# code do?

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It's a lambda expression that takes no parameter and returns true. The equivalent anonymous delegate is:

delegate() { return true; };

Most likely the method requires a parameter of type Func<bool>, which is a generic delegate with the same signature as above code.

EDIT:

As noted by cdhowie, the above lambda can also be evaluated to an expression tree of type Expression<Func<bool>>.

Here's the equivalent expression tree:

var body = Expression.Constant(true);
Expression<Func<bool>> returnsTrueExpression = Expression.Lambda<Func<bool>>(body);

You can 'convert' it to an actual delegate by calling Compile()

Func<bool> returnsTrueFunc = returnsTrueExpression.Compile();

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This is a lambda expression that always return true. This is a delegate that has functionality similar to this method

bool Test(){
  return true;
}

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The code reminds me of when you may want to stub or mock values in the early stages of creating unit tests.

You could have a class that has a method like:

bool result = SomeClass.RunSomeImportantProcess(Func<bool> process)

and in your tests you might want to do something as a stub like

Assert.IsTrue(SomeClass.RunSomeImportantProcess(() => true));

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Its a lambda expression which doesn't take any parameter but returns true. Whether its required or not, you would have to provide more info to determine.