How to return multiple values in C# 7?

What do you mean by natively?

C# 7 has a new feature that lets you return more than one value from a method thanks to tuple types and tuple literals.

Take the following function for instance:

(string, string, string) MyCoolFunction() // tuple return type
{   
    //...        
    return (firstValue, secondValue, thirdValue);
}

Which can be used like this:

var values = MyCoolFunction();
var firstValue = values.Item1;
var secondValue = values.Item2;
var thirdValue = values.Item3;

Or by using deconstruction syntax

(string first, string second, string third) = MyCoolFunction();

//...

var (first, second, third) = MyCoolFunction(); //Implicitly Typed Variables

Take some time to check out the Documentation, they have some very good examples (this answer's one are based on them!).

You are looking for Tuples. This is an example:

static (int count, double sum) Tally(IEnumerable<double> values)
{
    int count = 0;
    double sum = 0.0;
    foreach (var value in values)
    {
        count++;
        sum += value;
    }
    return (count, sum);
}

...

var values = ...
var t = Tally(values);
Console.WriteLine($"There are {t.count} values and their sum is {t.sum}");

Example stolen from http://www.thomaslevesque.com/2016/07/25/tuples-in-c-7/