Regular Expression to Replace Specific character between 2 immediate letters or numbers?

I'll gave it another try. This is my example text:

"Daft Punk, is great", "yes! they are, great"
"A B C D, E F G", "A B C D,E F G", "ABCD, EFG"

And here is my resulting text:

"Daft Punk - is great", "yes! they are - great"
"A B C D - E F G", "A B C D - E F G", "ABCD - EFG"

But, as often with Regex, if your text is irreguar the 'regular' expression won't help. Here comes my code snippet:

static void Main(string[] args) {
    string path = <pathOfYourCSV>;
    string destPath = <destPath>;
    var lines = File.ReadLines(path);
    string pattern = @"(?<=.+),\s?(?=.+)";
    string replacement = @" - ";
    string[] sep = new string[] {"\",", "\", "};
    FileStream fs = File.Open(destPath, FileMode.Append);
    StreamWriter sw = new StreamWriter(fs);
    foreach (var item in lines) {
        string[] linesArr = item.Split(sep, StringSplitOptions.RemoveEmptyEntries);
        string[] arr = new string[linesArr.Length];
        int cnt = 0;
        foreach (var i in linesArr) {
            if (String.IsNullOrEmpty(i)) break;
            Match match = Regex.Match(i, pattern);
            arr[cnt] = Regex.Replace(i, match.ToString(), replacement);
            cnt++;
        }
        Console.WriteLine(String.Join(",", arr).Replace(",", "\","));
        sw.WriteLine(String.Join(",", arr).Replace(",", "\","));
    }
    sw.Close();
    fs.Close();
    Console.ReadKey();
}