String.IndexOf()

String.IndexOf()

public List<string> ParseWords(string s)
{
    List<string> words = new List<string>();

    int pos = 0;
    while (pos < s.Length)
    {
        // Get word start
        int start = pos;

        // Get word end
        pos = s.IndexOf('|', pos);
        while (pos > 0 && s[pos - 1] == '\')
        {
            pos++;
            pos = s.IndexOf('|', pos);
        }

        // Adjust for pipe not found
        if (pos < 0)
            pos = s.Length;

        // Extract this word
        words.Add(s.Substring(start, pos - start));

        // Skip over pipe
        if (pos < s.Length)
            pos++;
    }
    return words;
}

string test = @"This|is|a|pip|ed|test (this is a pip|ed test)";
string[] parts = Regex.Split(test, @"(?<!(?<!\)*\)|");

string sPipeSplit = "This|is|a|pip\|ed|test (this is a pip|ed test)";
string sTempString = sPipeSplit.Replace("\|", "¬"); //replace | with non printable character
string[] sSplitString = sTempString.Split('|');
//string sFirstString = sSplitString[0].Replace("¬", "\|"); //If you have fixed number of fields and you are copying to other field use replace while copying to other field.
/* Or you could use a loop to replace everything at once
foreach (string si in sSplitString)
{
    si.Replace("¬", "\|");
}
*/

string text = @"This|is|a|pip|ed|test"; //The original text
string parsed = ""; //Where you will store the parsed string

bool flag = false;
foreach (var x in text.Split('|')) {
    bool endsWithArroba = x.EndsWith(@"");
    parsed += flag ? "|" + x + " " : endsWithArroba ? x.Substring(0, x.Length-1) : x + " ";
    flag = endsWithArroba;
}

/^(?:((?:[^|\]|(?:\{2})|\|)+)(?:||$))*/

^              #The start of a line
(?:...
    [^|\]     #A character other than | or  OR
    (?:\{2})* #An even number of  characters OR
    \|       #A literal  followed by a literal |
...)+          #Repeat the preceding at least once
(?:$||)       #Either a literal | or the end of a line