C# ternary operator for optional string parameter

Question

What is the correct/best way to handle the string as optional parameter in ternary operator:

public static void method(string s1, string s2="")
{
    var str = !string.IsNullOrEmpty(s2) ? s2.Equals("abc") ? "abcuser" : "xyzuser" : "xyzuser";
    Console.WriteLine(str);     
}

OR

public static void method(string s1, string s2="")
{
    var str = !string.IsNullOrEmpty(s2) && s2.Equals("abc") ? "abcuser" : "xyzuser";
    Console.WriteLine(str);     
}

Answer 1

When creating a ternary operator, it's important that you keep them as clean and simple as possible so it's easier for other developers to read. In this instance, I can't see a use for the "s1" parameter. If this is your entire method, I recommend removing it and keeping it simple. Your "s2" parameter must equal "abc" to be accepted. Hence, a null check is not required. However, if you ever need to use a check like this, I recommend using IsNullOrWhiteSpace() because it indicates whether a specified string is null, empty, or consists only of white-spaced characters. This means it will check if the string contains empty space as well. E.g. if "s2" = " ", IsNullOrEmpty() wouldn't pick that up. I will leave a code example below, with a commented out line using this string method to check for white space. However, in this instance, I suggest you only use the smaller line.

public static void method(string s1, string s2 = "") {
     //var str = !string.IsNullOrWhiteSpace(s2) && s2.Equals("abc") ? "abcuser"
       : "xyzuser";
       var str = s2 == "abc" ? "abcuser" : "xyzuser";
       Console.WriteLine(str);
}

Too make it cleaner and more optimized, if you are not using that var variable again, you could just do this.

public static void method(string s1, string s2 = "") {
            Console.WriteLine(s2 == "abc" ? "abcuser" : "xyzuser");
        }

Or another alternative would be to return this value as a string

public static string method(string s2 = "") {
            return s2 == "abc" ? "abcuser" : "xyzuser";
        }