using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		var text = @"<AC:Value> SYMBOL: PDWFNA     = 0;        // Projektierung D-Weg Freimeldung nicht
                                          // auswerten
<AC:Value> SYMBOL: PDWLE      = 0;        // Länge des Durchrutschweges";
		var matches = Regex.Matches(text, @"<\w{2}:Value> SYMBOL: (P.*)=(.*)//(.*(?:\n[\s-[\r\n]]*//.*)*)");
		foreach (Match m in matches) 
		{
			Console.WriteLine("--- A new match ---");
			Console.WriteLine($"Group 1: {m.Groups[1].Value}");
			Console.WriteLine($"Group 2: {m.Groups[2].Value}");
			Console.WriteLine("Group 3: {0}",
				string.Join(" ", 
					m.Groups[3].Value.Split(new[] {"//"}, StringSplitOptions.RemoveEmptyEntries)
						.Select(x => x.Trim())
				)
			);
		}
	}
}