问题
I just want to verify my understanding about the following
- Delegate - a method signature
- Lambdas - anonymous function
- Anonymous Function - just that
- Action - An anonymous function that returns nothing
- Func - An anonymous function that returns something
hmm... they all do similar things, how do you define & know when to use each?
sorry, I don't explain well
回答1:
Delegate - it is not a method signature.
It is a type which encapsulates a method. Hence a delegate declaration should have a signature similar to the method it wants to encapsulate.When to use Delegate - whenever you want to pass a method to another function.For more see this and this.Lambdas - short hand and more expressive way of writing an anonymous function. But there is more to it. A lambda expression can also be converted to an expression tree. For more see this.
Anonymous Function - yes .. just that
Action - It is a delegate which can encapsulate a function that returns nothing. So you should think of it as
a type that can encapsulate an actionand use it when you need to pass an action around.Func - A delegate that can encapsulate a function that returns something. But you should look at it as
a type that can encapsulate a transformationand use when you want to pass around a transformation.
回答2:
Action and Func are just special cases of the Delegate. Delegate itself is something that references a method and can be used to call it.
回答3:
Don't try to see C# + these features. Also because there is not a strict pragmatic answer to your question.
Start from a functional programming point of view, for example try to learn F# to get inside what and when lambdas are used (actually everywhere inside a functional language) and then you'll understand things better.
It will open your mind and make you think differently about imperative programming or mixed languages like C#.
来源：https://stackoverflow.com/questions/4275269/delegates-lambdas-action-func-anonymous-functions