using static System.Console;

​

public class Program {

    public static void Main() {

        var text = "text";

        ChangeText(text);

        WriteLine(text);

        ChangeText(ref text);

        WriteLine(text);

    }

    static void ChangeText(string text) => text = "new text";

    static void ChangeText(ref string text) => text = "new text";

​

}