C#•3mo ago

✅ Check if an item is in a list

For this if statement, how do i make it so if the parameter customer is not in the list, then it adds it to the list

20 Replies

Angius•3mo ago

.Contains() for example

Ewan•3mo ago

Angius•3mo ago

Or .Any() with a predicate

Ewan•3mo ago

gotcha thank you!

Angius•3mo ago

Or use a hashset, it deduplicates automatically

Ewan•3mo ago

got it thanks!

Angius•3mo ago

Not sure how well it works with reference types, though. Might need either some overrides on the type or a custom comparer for the hashset

Ewan•3mo ago

if (!_customers.Contains(customer)) { _customers.Add(customer); } } i mean this works right?

Angius•3mo ago

Well, reference types use reference comparison So it works if a reference to that particular customer exists on the _customers list

Ewan•3mo ago

ah ok i havnt learnt hashsets so im good

MODiX•3mo ago

Angius

REPL Result: Success

class Foo(string name)
{
    public string Name { get; set; } = name;
}

List<Foo> foos = [ new Foo("Bob") ];
var bob = new Foo("Bob");

foos.Contains(bob)

class Foo(string name)
{
    public string Name { get; set; } = name;
}

List<Foo> foos = [ new Foo("Bob") ];
var bob = new Foo("Bob");

foos.Contains(bob)

Result: bool

False

False

Compile: 426.010ms | Execution: 42.391ms | React with ❌ to remove this embed.

Angius•3mo ago

As you can see Different references

Ewan•3mo ago

oh i see oh right well they are named different

Angius•3mo ago

Values inside of the class don't matter whatsoever, only the reference

Ewan•3mo ago

right

Angius•3mo ago

When it comes to .Contains() at least

Ewan•3mo ago

ok gotcha

Angius•3mo ago

.Any() with a predicate might be safer

MODiX•3mo ago

Angius

REPL Result: Success

class Foo(string name)
{
    public string Name { get; set; } = name;
}

List<Foo> foos = [ new Foo("Bob") ];
var bob = new Foo("Bob");

foos.Any(f => f.Name == bob.Name)

class Foo(string name)
{
    public string Name { get; set; } = name;
}

List<Foo> foos = [ new Foo("Bob") ];
var bob = new Foo("Bob");

foos.Any(f => f.Name == bob.Name)

Result: bool

True

True

Compile: 425.404ms | Execution: 102.865ms | React with ❌ to remove this embed.

Ewan•3mo ago

its just a little program, it works so its fine haha oooo i see thanks!

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✅ Check if an item is in a list