Escape character in C#'s Split()

Question

I am parsing some delimiter separated values, where ? is specified as the escape character in case the delimiter appears as part of one of the values.

For instance: if : is the delimiter, and a certain field the value 19:30, this needs to be written as 19?:30.

Currently, I use string[] values = input.Split(':'); in order to get an array of all values, but after learning about this escape character, this won't work anymore.

Is there a way to make Split take escape characters into account? I have checked the overload methods, and there does not seem to be such an option directly.

Answer 1

string[] substrings = Regex.Split("aa:bb:00?:99:zz", @"(?<!\?):");

for

aa
bb
00?:99
zz

Or as you probably want to unescape ?: at some point, replace the sequence in the input with another token, split and replace back.

(This requires the System.Text.RegularExpressions namespace to be used.)

Answer 2

This kind of stuff is always fun to code without using Regex.

The following does the trick with one single caveat: the escape character will always escape, it has no logic to check for only valid ones: ?;. So the string one?two;three??;four?;five will be split into onewo, three?, fourfive.

 public static IEnumerable<string> Split(this string text, char separator, char escapeCharacter, bool removeEmptyEntries)
 {
     string buffer = string.Empty;
     bool escape = false;

     foreach (var c in text)
     {
         if (!escape && c == separator)
         {
             if (!removeEmptyEntries || buffer.Length > 0)
             {
                 yield return buffer;
             }

             buffer = string.Empty;
         }
         else
         {
             if (c == escapeCharacter)
             {
                 escape = !escape;

                 if (!escape)
                 {
                     buffer = string.Concat(buffer, c);
                 }
             }
             else
             {
                 if (!escape)
                 {
                     buffer = string.Concat(buffer, c);
                 }

                 escape = false;
             }
         }
     }

        if (buffer.Length != 0)
        {
            yield return buffer;
        }
    }