Other ways to deal with “loop initialization” in C#

Question

To start with I\'ll say that I agree that goto statements are largely made irrelevant by higher level constructs in modern programming languages and shouldn\'t be used when

Answer 1

You can certainly create a goto solution in C# (note: I didn't add null checks):

string Join(string[] array, string delimiter) {
  var sb = new StringBuilder();
  var enumerator = array.GetEnumerator();
  if (enumerator.MoveNext()) {
    goto start;
    loop:
      sb.Append(delimiter);
      start: sb.Append(enumerator.Current);
      if (enumerator.MoveNext()) goto loop;
  }
  return sb.ToString();
}

For your specific example, this looks pretty straighforward to me (and it's one of the solutions you described):

string Join(string[] array, string delimiter) {
  var sb = new StringBuilder();
  foreach (string element in array) {
    sb.Append(element);
    sb.Append(delimiter);
  }
  if (sb.Length >= delimiter.Length) sb.Length -= delimiter.Length;
  return sb.ToString();
}

If you want to get functional, you can try using this folding approach:

string Join(string[] array, string delimiter) {
  return array.Aggregate((left, right) => left + delimiter + right);
}

Although it reads really nice, it's not using a StringBuilder, so you might want to abuse Aggregate a little to use it:

string Join(string[] array, string delimiter) {
  var sb = new StringBuilder();
  array.Aggregate((left, right) => {
    sb.Append(left).Append(delimiter).Append(right);
    return "";
  });
  return sb.ToString();
}

Or you can use this (borrowing the idea from other answers here):

string Join(string[] array, string delimiter) {
  return array.
    Skip(1).
    Aggregate(new StringBuilder(array.FirstOrDefault()),
      (acc, s) => acc.Append(delimiter).Append(s)).
    ToString();
}