using System;

public class Program

{

    public static void Main()

    {

        string input = "1.7,2015-05-21T09:18:58;";

        string output = FindStringInBetween(input, ",", ";");

        Console.WriteLine(output);

    }

    public static string FindStringInBetween(string Text, string FirstString, string LastString)

    {

        string STR = Text;

        string STRFirst = FirstString;

        string STRLast = LastString;

        string FinalString;

        int Pos1 = STR.IndexOf(FirstString) + FirstString.Length;

        int Pos2 = STR.IndexOf(LastString);

        FinalString = STR.Substring(Pos1, Pos2 - Pos1);

        return FinalString;

    }

}