Enums I thought they were safe to use

[Guest]

I've been using enum as input parameter to methods in the belief that this
was a safe method of restricting the input parameters, but the example below
proves me wrong.
Is there a way to prevent this?

class Program {
enum ValidColor {
Red = 1,
Blue = 2
}

static void PrintColor(ValidColor color){
switch (color){
case ValidColor.Blue:
case ValidColor.Red:
Console.WriteLine("OK: " + (int)color);
break;
default:
Console.WriteLine("NOT OK!: " + (int)color);
break;
}
}
static void Main(string[] args) {
PrintColor(ValidColor.Blue);
PrintColor(ValidColor.Red);

//make illigal color
ValidColor invalidColor = (ValidColor)22;
PrintColor(invalidColor);

Console.ReadLine();
}
}



ps. I use VS 2005 Beta 2

 

[Guest]

Hi,

Using Enums does not gurantee the value passed falls within the enum range
defined. You need to validate this youself.

Eg. for validation:
if(color < ValidColor.Red || color > ValidColor.Blue )
{
throw new ArgumentException("Invalid Color");
}

 

[Guest]

A better test is

if(Enum.isDefined(typeof(ValidColor), color))
throw new ArgumentException("Invalid Color");

which works however many entries are in the enum

Hi,

Using Enums does not gurantee the value passed falls within the enum range
defined. You need to validate this youself.

Eg. for validation:
if(color < ValidColor.Red || color > ValidColor.Blue )
{
throw new ArgumentException("Invalid Color");
}

--
HTH,
Rakesh Rajan
MVP, MCSD
http://www.msmvps.com/rakeshrajan/

I've been using enum as input parameter to methods in the belief that this
was a safe method of restricting the input parameters, but the example below
proves me wrong.
Is there a way to prevent this?

class Program {
enum ValidColor {
Red = 1,
Blue = 2
}

static void PrintColor(ValidColor color){
switch (color){
case ValidColor.Blue:
case ValidColor.Red:
Console.WriteLine("OK: " + (int)color);
break;
default:
Console.WriteLine("NOT OK!: " + (int)color);
break;
}
}
static void Main(string[] args) {
PrintColor(ValidColor.Blue);
PrintColor(ValidColor.Red);

//make illigal color
ValidColor invalidColor = (ValidColor)22;
PrintColor(invalidColor);

Console.ReadLine();
}
}



ps. I use VS 2005 Beta 2

 

[Guest]

Ok, i've just misunderstood how Enums worked then.

Bu what if you have a realy huge Enum, and don't want to do validation. What
should you use instead?

 

[Steve]

enum Colors : int
{
ColorRed = 0,
//..,
//..,
ColorInvalidColor
}


if(value >= Colors.ColorRed && value < Colors.ColorInvalidColor)
{}


Pretty much exactly what the first responder did, but reads a little nicer
(IMO)
Might be dumb, I dunno.. that's what I do.

 

[Guest]

This will help, but as i asked: what can i use if i don't want to do
validation?

/Rasmus

 

[Oliver Sturm]

This will help, but as i asked: what can i use if i don't want to do
validation?

If you want a data type that'll always be valid, you'll have to create
your own type in the form of a struct or a class. But if that data type is
being constructed with the help of other, integral, types, you'll have to
do validation again, though in a different place - remember that within
the constraints posed by your application model and the methods you write
for it, you're the only one who can judge the validity of a given set of
information.



Oliver Sturm