Sorting Multiple Lists

Question

I have 3 List containing : Index, Name, Age

Example:

List<int> indexList = new List<int>();
indexList.Add(3);
indexList.Add(1);
indexList.Add(2);
List<string> nameList = new List<string>();
nameList.Add("John");
nameList.Add("Mary");
nameList.Add("Jane");
List<int> ageList = new List<int>();
ageList.Add(16);
ageList.Add(17);
ageList.Add(18);

I now have to sort all 3 list based on the indexList.

How do I use .sort() for indexList while sorting the other 2 list as well

Answer 1

You are looking at it the wrong way. Create a custom class:

class Person
{
     public int Index { get; set; }
     public string Name{ get; set; }
     public int Age{ get; set; }
}

Then, sort the List<Person> with the help of the OrderBy method from the System.Linq namespace:

List<Person> myList = new List<Person>() {
    new Person { Index = 1, Name = "John", Age = 16 };
    new Person { Index = 2, Name = "James", Age = 19 };
}
...

var ordered = myList.OrderBy(x => x.Index);

Also, you can read Jon Skeet article about your anti-pattern.

Answer 2

Farhad's answer is correct and should be accepted. But if you really have to sort three related lists in that way you could use Enumerable.Zip and OrderBy:

var joined = indexList.Zip(
        nameList.Zip(ageList, (n, a) => new { Name = n, Age = a }), 
            (ix, x) => new { Index = ix, x.Age, x.Name })
        .OrderBy(x => x.Index);
indexList = joined.Select(x => x.Index).ToList();
nameList = joined.Select(x => x.Name).ToList();
ageList = joined.Select(x => x.Age).ToList();

All are ordered by the value in the index-list afterwards.