C# 7.0 introduced ref return ^{C# 7.0} and ref local ^{C# 7.0}, allowing methods to return references to variables. However, the conditional operator ?: didn't support ref expressions, limiting the ability to conditionally select between references.

C# 7.2 extends the conditional operator to work with ref expressions, allowing you to conditionally choose between two references without copying values.

Code

Now

ref int GetReference(int[] array, bool useFirst)
{
    return ref (useFirst ? ref array[0] : ref array[^1]);
}

int[] numbers = { 10, 20, 30 };
ref int value = ref GetReference(numbers, true);
value = 100;  // numbers[0] is now 100

Before

ref int GetReference(int[] array, bool useFirst)
{
    if (useFirst)
        return ref array[0];
    else
        return ref array[^1];
}

int[] numbers = { 10, 20, 30 };
ref int value = ref GetReference(numbers, true);
value = 100;  // numbers[0] is now 100

Notes

• Both branches of the conditional expression must be ref expressions
• The ref keyword must appear before both the conditional operator and each branch
• This works with ref readonly as well for read-only references
• All expressions must return compatible ref types

More information

• Specification
• Ref returns and ref locals