// If you need to convert a string to a double you can use this :
var string = "12,05";
var double = Convert.toDouble(string); // This will be a double with the value of 12,05
// If for some reason you need to convert a string with a "." instead of a "," do this :
var string = "12.05";
var double = Convert.ToDouble(string.Replace(".", ",")); // And this will be the same as previous one
Console.WriteLine(Convert.ToDouble("52,8725945"));