Question

What is the regular expression to allow for numbers between -90.0 and +90.0? The numbers in between can be floating or whole numbers.

Answer 1

I don’t think you want to use a Regex for this. Use Double.Parse() (or Double.TryParse()) if your data is stored in a string, and then check the resulting value to ensure that it falls within the desired range. For example:

public bool IsInRange(string value)
{
   bool isInRange = false;

   double parsed = 0;
   if (Double.TryParse(value, out parsed))
   {
      // use >= and <= if you want the range to be from -90.0 to 90.0 inclusive
      isInRange = value > -90.0 && value < 90.0;
   }

   return isInRange;
}

If your value is already a double, then it’s even easier — no parsing required.