Linq – How to use LINQ to obtain a unique list of properties from a list of objects

c#-3.0classlinqlistproperties

I'm trying to use LINQ to return a list of ids given a list of objects where the id is a property. I'd like to be able to do this without looping through each object and pulling out the unique ids that I find.

I have a list of objects of type MyClass and one of the properties of this class is an ID.

public class MyClass
{
  public int ID { get; set; }
}

I want to write a LINQ query to return me a list of those Ids.

How do I do that, given an IList<MyClass> such that it returns an IEnumerable<int> of the ids?

I'm sure it must be possible to do it in one or two lines using LINQ rather than looping through each item in the MyClass list and adding the unique values into a list.

Best Answer

IEnumerable<int> ids = list.Select(x=>x.ID).Distinct();

Related Solutions

Python – How to check if a list is empty

if not a:
  print("List is empty")

Using the implicit booleanness of the empty list is quite pythonic.

Python – How to randomly select an item from a list

Use random.choice():

import random

foo = ['a', 'b', 'c', 'd', 'e']
print(random.choice(foo))

For cryptographically secure random choices (e.g., for generating a passphrase from a wordlist), use secrets.choice():

import secrets

foo = ['battery', 'correct', 'horse', 'staple']
print(secrets.choice(foo))

secrets is new in Python 3.6. On older versions of Python you can use the random.SystemRandom class:

import random

secure_random = random.SystemRandom()
print(secure_random.choice(foo))

Best Answer

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Python – How to check if a list is empty

Python – How to randomly select an item from a list

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