How to convert string to integer and determine if it's less than Int32.MinValue or greater than Int32.MaxValue?

I have the following piece of code which attempts to determine whether a given string is a valid integer. If it's an integer, but not within the valid range of Int32, I need to know specifically whether it's greater than Int32.MaxValue or less than Int32.MinValue.

try
{
     return System.Convert.ToInt32(input);
}
catch (OverflowException)
{
     return null;
}
catch (For开发者_StackOverflow社区matException)
{
     return null;
}

Convert.ToInt32 will throw the OverflowException if it's not in the range of acceptable values, but it throws the same exception for both greater than and less than. Is there a way to determine which one it is aside from parsing out the text of the exception?

As you're using .NET 4, you could use BigInteger - parse to that, and then compare the result with the BigInteger representations of int.MaxValue and int.MinValue.

However, I would urge you to use TryParse instead of catching an exception and using that for flow control.

You could convert it to Int64 (i.e. long) instead, and then do the comparison yourself. That will also eliminate an exception as control flow situation.

There is a very simple way to know if the input that threw an OverflowException (or gave a false if you used TryParse) is more than Int32.MaxValue or less than Int32.MinValue: a number less than Int32.MinValue will be a negative one, so its string representation will begin with a '-' !

The idea is:

bool isWrong = false;
bool isLarge = false;
if (!Int32.TryParse(rawValue, out int32Holder))
{
      if (!Int64.TryParse(rawValue, out int64Holder))
      {
           isWrong = true;
      }
      else
      {
           isLarge = true;
      }
}