.ToString() on non specified Exception.HelpLink

[Kurt]

I wonder why the .ToString() methode of line 20 failes....
Some more questions;
1/ Is a string actually a value type or a reference type?
2/ If a string is a value type, what is the default initial value for the strings of an array of strings that is instantiated ("", null or String.Empty???)?
3/ And what is the value of the Exception.HelpLink string when not specified?
By the way, ToString() seems to work on String.Empty....

[CS]
namespace Tests
{
using System;

public class Test
{
public static void Main()
{
try
{
double a = 6;
double b = 0;
Console.WriteLine("{0} / {1} = {2}",a,b,Divide(a,b));
}
catch (DivideByZeroException divByZero)
{
//the folowing line WORKS, HelpLink property is seen as "" (empty string)
Console.WriteLine("Help on error: '{0}'\n\n",divByZero.HelpLink);
//the folowing line THROWS AN EXCEPTION, WHY ????
Console.WriteLine("Help on error: '{0}'\n\n",divByZero.HelpLink.ToString());
}
}

public static double Divide(double a, double b)
{
if (b == 0)
{
DivideByZeroException e = new DivideByZeroException("Argument b was 0 in DoDivision (dividing by zero)");
//folowing line is commented to see what the HelpLink property contains by default....
//e.HelpLink = "More about dividing by zero...";
throw e;
}
return a/b;
}
}

}
[/CS]

 

[dynamic_sysop]

if divByZero.HelpLink is empty ( ie: "" ) , you cant use ToString() because you can't convert " Nothing " to a String , there needs to be a value there. But by the look of it , divByZero.HelpLink is a string based result anyway , so it shouldnt need ToString() on the end of it.

 

[Kurt]

It shouldn't need it, but an exception shouldn't be thrown either when ToString() is called - a methode overritten by the String class, no harm to call it - and this while...

System.Console.WriteLine(System.String.Empty.ToString());

doesn't throw any exceptions.

ps:

1/ Is a string actually a value type or a reference type?

I know that strings are immutable, and so act like value types when passed to a methode. On the other hand however, System.String doesn't inherit from System.ValueType as value types seem to do... some more info is very welcome....