using System;

public class Program

{

    public static void Main()

    {

        double x = 10.00;

        bool isDecimal = false;

        if(x is double d)

            isDecimal = true;

        Console.WriteLine(isDecimal);

        var y = (decimal) x;

        Console.WriteLine(y);

//      if (value is double d) return (decimal) d;

​

//                return stringValue.Contains("e")

//                    ? decimal.Parse(stringValue, NumberStyles.Float, Culture)

 //                   : decimal.Parse(stringValue, Culture);

    }

}