read user input of double type

Try this:

double Salary = Convert.ToDouble(Console.ReadLine());

You'll have to check the entire thing on it's way in.. as Console.Read() returns an integer.

double totalSalary;
if (!double.TryParse(Console.ReadLine(), out totalSalary)) {
    // .. error with input
}
// .. totalSalary is okay here.

Simplest answer to your question:

double d = Double.Parse(Console.Readline());