Select an object that matches my condition using linq

Question

I have a list of Person types that have 3 properties Id, Name, Age

var per1 = new Person((1, "John", 33); var per2 = new Person((2, "Anna", 23); var persons = new List<Person>(); persons.Add(per1); persons.Add(per2); 

using linq I want to select a person whose age is the same as my input, for example 33.

I know how to use any, but I don’t know how to choose an object that matches my condition.

Answer 1

For one match:

 var match = persons.Single(p => your condition); 

For many matches, use persons.Where(condition) . There are also many choices for just one person, such as FirstOrDefault, First, Last, LastOrDefault and SingleOrDefault. Each of them has slightly different semantics depending on what exactly you want.

Answer 2

You can use Enumerable.Where and it will return all collections of matching elements.

 var res = persons.Where(c=>c.AttributeName == 23); 

If you want to make sure that you have only a match, you can use single.

 var res = persons.Single(c=>c.AttributeName == 23); 

Single Returns a single element of a sequence and throws an exception if the sequence does not contain exactly one element.

Answer 3

It is very simple.

 var per1 = new Person(1, "John", 33); var per2 = new Person(2, "Anna", 23); var persons = new List<Person>(); persons.Add(per1); persons.Add(per2); var sirec = persons.Select(x => x.age = 33); 

Try it and let me know

Note. If this is a single value, use "Single" instead of "Select"