using System;
public class Test
{
static void Swap(ref string a, ref string b) {
string c = b;
b = a;
a = c;
}
public static void Main()
{
string a = "a";
string b = "b";
string alsoA = a;
Swap(ref a, ref b);
Console.WriteLine(a); // B
Console.WriteLine(b); // A
Console.WriteLine(alsoA); // A
}
}
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