Good Practice (Part 2)

Today a quick follow-up on code legibility.
As usual all should be self-explanatory.

static void BadPractice5() {
    string a = null;
    string b = "hello";
    string c = string.Empty;

    string s;
    if (a != null) s = a;
    else if (b != null) s = b;
    else s = c;
} //

static void GoodPractice5() {
    string a = null;
    string b = "hello";
    string c = string.Empty;

    string s = a ?? b ?? c;
} //

static void BadPractice6() {
    string s = "12345";
    // s.Length is called multiple times
    for (int i = 0; i < s.Length; i++) {
        Console.WriteLine(s[i]);
        //s = "a";   // uncomment to see that "i < s.Length" is evaluated over and over again
    }
} //

static void GoodPractice6() {            
    string s = "12345";
    for (int i = 0, n = s.Length; i < n; i++)
        Console.WriteLine(s[i]); // s.Length is only called once
} //

static void BadPractice7() {
    string s = string.Empty;

    for (int i = 0; i < 100; i++) s += i.ToString() + " ";
    Console.WriteLine(s);
    Console.ReadLine();
} //

static void GoodPractice7() {
    // Use the StringBuilder class for multiple string concatenations!
    // Strings are immutable, concatenations are very slow.
    string s = string.Empty;
    StringBuilder lStringBuilder = new StringBuilder();

    for (int i = 0; i < 100; i++) {
        lStringBuilder.Append(i);
        lStringBuilder.Append(" ");
    }
    s = lStringBuilder.ToString();
    Console.WriteLine(s);
    Console.ReadLine();
} //

static void BadPractice8() {
    string s = string.Empty;

    do {
        s = Console.ReadLine();
        if (s == string.Empty) break;
    } while (true);
} //

static void GoodPractice8() {
    string s = string.Empty;

    while (true) {
        s = Console.ReadLine();
        if (string.IsNullOrEmpty(s)) break;
    }
} //

static void BadPractice9() {
    var lList = Enumerable.Range(1, 10); // imagine it is a grow only list

    // bad
    foreach (var i in lList) {
        Console.WriteLine(i);
    }
    Console.ReadLine();


    // also bad
    for (int i = 0, n = lList.Count(); i < n; i++) {
        Console.WriteLine(lList.ElementAt(i));
    }
    Console.ReadLine();
} //

static void GoodPractice9() {
    var lList = Enumerable.Range(1, 10); // imagine it is a grow only list

    // This is for real hardcore multithreading coders:
    // If poosibe walk through the list backwards and you can add elements
    // to the list concurrently without the need to synchronize anything.
    // No lock() required in a multithreading environment!
    for (int i = lList.Count() - 1; i > -1; i--) {
        Console.WriteLine(lList.ElementAt(i));
    }   
  Console.ReadLine();
} //