How to get value from IEnumerable collection using its Key?

If you want to retrieve a Customer name from a collection by its Id:

public string GetCustomerName(IEnumerable<Customer> customers, int id)
{
    return customers.First(c => c.Id == id).Name;
}

Using LINQ you can get all customers names (values) having specific value in this way:

var valuesList = items.Where(x => x.Something == myVar).Select(v => v.Name).ToList();

For single customer name you can do this:

var singleName = items.FirstOrDefault(x => x.Id == 1)?.Name;

Obviously, the Id can be 1, 2 or any other.

Edit:

I recommend you List<Customer> instead of Customer[]

So,

var items = new List<Customer> 
{ 
     new Customer { Name = "test1", Id = 999 }, 
     new Customer { Name = "test2", Id = 989 } 
};

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