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

public class Test
{
	public static void Main()
	{
		var str = "A tab\there \"inside\ta\tdouble-quoted\tsubstring\" some\there";
		var pattern = "\"[^\"]+\""; // A pattern to match a double quoted substring with no escape sequences
    	var result = Regex.Replace(str, pattern, m => 
    			m.Value.Replace("\t", "-")); // Replace the tabs inside double quotes with -
        Console.WriteLine(result);
	}
}