TeamCity Message Encoding.cs

static void Message(string format, params string[] args)
{
    var encodedArgs = args.Select(Encode).Cast<object>().ToArray();
    Console.WriteLine("##teamcity["+format+"]", encodedArgs);
}

static string Encode(string value)
{
    var builder = new StringBuilder();
    
    foreach (var ch in value)
    {
        switch (ch)
        {
            case '|': builder.Append("||"); break;
            case '\'': builder.Append("|'"); break;
            case '[': builder.Append("|["); break;
            case ']': builder.Append("|]"); break;
            case '\n': builder.Append("|n"); break; // Line Feed
            case '\r': builder.Append("|r"); break; // Carriage Return
            case '\u0085': builder.Append("|x"); break;  // Next Line
            case '\u2028': builder.Append("|l"); break;  // Line Separator
            case '\u2029': builder.Append("|p"); break;  // Paragraph Separator
            default: builder.Append(ch); break;
        }
    }

    return builder.ToString();
}