Need help understanding lambda statements and delegates - C#

ero

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ero•10/30/22, 1:02 PM

What exactly is confusing you? You can write any lambda as a full method, if that helps?

ero

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ero•10/30/22, 1:03 PM

canton7

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canton7•10/30/22, 1:15 PM

More details please. What exactly is confusing you?

ero

Eero ```cs Func<string, int> parse = input => int.Parse(input); ``` ```cs int Parse(s...

surwren

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surwrenOP•10/30/22, 1:50 PM

Yea so why does this look utterly different from the middleware lambda?

surwren

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surwrenOP•10/30/22, 1:52 PM

I know a lambda basically lacks a method name

surwren

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surwrenOP•10/30/22, 1:52 PM

It's just parameters => dosomething

ero

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ero•10/30/22, 1:52 PM

surwren

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surwrenOP•10/30/22, 1:52 PM

But why is the syntax so drastically different between lambdas used in middleware, delegate, and other functions?

ero

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ero•10/30/22, 1:53 PM

different in what way?

surwren

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surwrenOP•10/30/22, 1:54 PM

surwren

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surwrenOP•10/30/22, 1:55 PM

The parameters aren't even lined up the same way

surwren

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surwrenOP•10/30/22, 1:55 PM

I don't get it

surwren

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surwrenOP•10/30/22, 1:55 PM

In the first one the return type is int and input is string

surwren

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surwrenOP•10/30/22, 1:55 PM

But they are both inside of func <>

surwren

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surwrenOP•10/30/22, 1:56 PM

And then in the second, both context and next are input parameters and there is no return type specified in the lambda

surwren

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surwrenOP•10/30/22, 1:57 PM

Why is there no consistency between the syntaxes?

surwren

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surwrenOP•10/30/22, 1:57 PM

There are no patterns

surwren

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surwrenOP•10/30/22, 1:57 PM

Or at least my stupid brain can't see the patterns

surwren

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surwrenOP•10/30/22, 1:57 PM

I can only recognize that => indicates to dosomething

surwren

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surwrenOP•10/30/22, 1:58 PM

But i keep getting tripped up by the lambda signature

surwren

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surwrenOP•10/30/22, 1:58 PM

It seems that the signature changes every time it's used and it drives me crazy because I can't figure out why

ero

Eero ```cs Func<string, int> parse = input => int.Parse(input); ``` ```cs int Parse(s...

surwren

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surwrenOP•10/30/22, 1:59 PM

Ok for example

what does that even mean?

ero

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ero•10/30/22, 1:59 PM

is the lambda's name

ero

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ero•10/30/22, 2:00 PM

just like any other variable

ero

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ero•10/30/22, 2:00 PM

ero

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ero•10/30/22, 2:00 PM

ero

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ero•10/30/22, 2:00 PM

i could have named it if you prefer that

ero

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ero•10/30/22, 2:00 PM

is the

string

string

parameter's name

ero

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ero•10/30/22, 2:00 PM

just like in the full method body below

ero

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ero•10/30/22, 2:01 PM

ero

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ero•10/30/22, 2:01 PM

i could have wrapped in parens if you prefer that

ero

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ero•10/30/22, 2:01 PM

ero

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ero•10/30/22, 2:01 PM

what you're using in is an anonymous function, one which doesn't have a name

ero

Eero `Func<string, int> myLambda = (input) => int.Parse(input);`

surwren

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surwrenOP•10/30/22, 2:02 PM

But why is input even there, and missing a type declaration?

ero

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ero•10/30/22, 2:02 PM

so all that remains is

ero

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ero•10/30/22, 2:02 PM

the type declaration is in the type

ero

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ero•10/30/22, 2:02 PM

takes in one string parameter, and returns one integer

surwren

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surwrenOP•10/30/22, 2:04 PM

So the return type of a lambda is always the last value of the

declaration?

ero

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ero•10/30/22, 2:05 PM

indeed

surwren

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surwrenOP•10/30/22, 2:05 PM

Return would be bool

Return would be List<int>?

ero

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ero•10/30/22, 2:06 PM

mhm

surwren

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surwrenOP•10/30/22, 2:06 PM

So then the variable names (x, y) correspond in order with the int,int declarations in Func (for the first lambda)?

ero

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ero•10/30/22, 2:06 PM

yup

surwren

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surwrenOP•10/30/22, 2:07 PM

If it was Func<int,string,int> trial = (a,b)=>

It would be int a, string b

ero

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ero•10/30/22, 2:07 PM

yup

ero

Eero what you're using in `app.Use()` is an anonymous function, one which doesn't hav...

surwren

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surwrenOP•10/30/22, 2:08 PM

I still dont get this

ero

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ero•10/30/22, 2:08 PM

you can actually declare them explicitly

ero

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ero•10/30/22, 2:08 PM

surwren

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surwrenOP•10/30/22, 2:08 PM

Ah

ero

Eero you can actually declare them explicitly

surwren

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surwrenOP•10/30/22, 2:09 PM

But it needs to match the Func<> declaration?