using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string input = "    <ClCompile Include=\"..\\Utils\\Maths\\BcurveDef.cpp\">";

        string output = Test(input);

        Console.WriteLine(output);

    }

    private static readonly Regex Pattern = new Regex("(?<==\")\\S*.c(xx|pp|c)", RegexOptions.Compiled);

​

    public static string Test(string input)

    {

        if (Pattern.IsMatch(input))

        {

            MatchCollection matches = Pattern.Matches(input);

            string stringsOut = "matches: ";

            foreach (Match match in matches)

            {

                stringsOut += match.Value;

                stringsOut += ", ";

            }

            return stringsOut;

        }

        else

        {

            return "nope";

        }

    }

}