using System;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main()

    {

        var x = ""; 

        var y = "dslfsdf"; 

        car t = null;

        var santise = Regex.Replace("t?3453--45.valu343e+-", "[^0-9\\-]+", "");

        Console.WriteLine(santise);

    }

}

public class car {

    public string value; 

}