I'd like to pass an element of an array (array contains value type elements, not ref type) by reference.
Is this possible? Thank you
2 Answers
Yes, that's absolutely possible, in exactly the same way as you pass any other variable by reference:
using System;
class Test
{
static void Main(string[] args)
{
int[] values = new int[10];
Foo(ref values[0]);
Console.WriteLine(values[0]); // 10
}
static void Foo(ref int x)
{
x = 10;
}
}
This works because arrays are treated as "collections of variables" so values[0] is classified as a variable - you wouldn't be able to do a List<int>, where list[0] would be classified as a value.
Comments
As an addition to Jon's answer, from C# 7 you can now do this kind of thing inline without the need for a wrapping method, with a "ref local". Note the need for the double usage of the "ref" keyword in the syntax.
static void Main(string[] args)
{
int[] values = new int[10];
ref var localRef = ref values[0];
localRef = 10;
//... other stuff
localRef = 20;
Console.WriteLine(values[0]); // 20
}
This can be useful for situations where you need to refer to or update the same position in an array many times in a single method. It helps me to to avoid typos, and naming the variable stops me forgetting what array[x] refers to.
Links: https://www.c-sharpcorner.com/article/working-with-ref-returns-and-ref-local-in-c-sharp-7-0/ https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/ref-returns
refkeyword.