Convert.ToDouble(String) does not throw an overflow exception when max_value is exceeded

Question

I use .NET 8.0 on vscode. In documentation (for .NET 8.0) of Convert.ToDouble(String) there is OverFlow Exception when Double.MaxValue is exceeded, but when I convert a string that represents a value>Double.MaxValue, it doesn't throw an exception, but give me a double with particular value.

using System;

public class Example
{
   public static void Main()
   {
     string? s_num = "1.7976931348623157E+400"; //>Double.MaxValue
     double num = Convert.ToDouble(s_num); //i'm expecting an Overflow Exception
     Console.WriteLine(num.ToString()); //output: 8
   }
}

Answer 1

The behavior you're experiencing is due to the fact that the Convert.ToDouble(string) method uses the double.Parse(string) method internally. When you pass a string representing a value greater than Double.MaxValue, the double.Parse(string) method returns Double.PositiveInfinity instead of throwing an OverflowException.

Here's the modified code to demonstrate this:

using System;

public class Example
{
   public static void Main()
   {
      string s_num = "1.7976931348623157E+400"; // > Double.MaxValue
      double num = Convert.ToDouble(s_num); // Returns Double.PositiveInfinity, not OverflowException
      Console.WriteLine(num.ToString()); // Output: ∞
      
      if (double.IsInfinity(num))
      {
          Console.WriteLine("The value is greater than Double.MaxValue");
      }
   }
}

To handle cases when the parsed value is greater than Double.MaxValue, you can check for double.IsInfinity(num) and handle it accordingly.