C# App: Problems with ArrayList

[dhyder]

This project is using .NET and C#. Although my problem is with C# syntax (I think) I didn't see a C# board to post this on. So sorry if this is in the wrong spot.

Basically my problem is trying to get my ArrayList of integers to post after someone is done entering them.

public static void numberArray()
        {
            Console.WriteLine("\nEnter some numbers into an array.");
            Console.WriteLine("A null value will display the array.\n");
            ArrayList numbers = new ArrayList();
            Int32? inputNum = Convert.ToInt32(Console.ReadLine()); //Made it Nullable
            while (inputNum.HasValue) //checks to see if inputNum is null
            {                            //when it's null, the loop will end
                try
                {
                    numbers.Add(inputNum); //if not null, adds to array
                    Console.WriteLine("Number inserted!\n");
                    inputNum = Convert.ToInt32(Console.ReadLine()); 
                 //error is here, when I leave it blank to exit the loop 
                 //and continue, I get a datatype error. 
                }
                catch (Exception ex)
                {
                    Console.WriteLine("An error occured: " + ex.Message);
                }        
            }
            foreach (Int32 i in numbers)
            {
                Console.WriteLine(i);
            }
            Console.Read();
        }
 

I understand why I am getting the error. I can't Convert a blank\null value entered to Int32. My question is what is another way I can do this?

I also have a StringCollection in a similar program:

public static void stringCollect()
        {
            Console.WriteLine("\nEnter some strings and senteces into a collection.");
            Console.WriteLine("An empty string will display the collection.\n");
            StringCollection strCol = new StringCollection();
            string inputString = Console.ReadLine();
            while (inputString != "")         //Does this until empty string is inserted
            {
                try                             //Exception handling for each string entered.
                {
                    strCol.Add(inputString);         //Add string to collection
                    Console.WriteLine("String inserted\n"); //Tell string was inserted
                    inputString = Console.ReadLine();     //New readline for new string
                }
                catch (Exception ex)
                {
                    Console.WriteLine("An error occured: " + ex.Message);
                }
            }
            foreach (string str in strCol) //Displays all strings in the collection
            { 
                Console.WriteLine(str);                 
            }                                         
            Console.Read();
        }
 

It works perfect and I was trying to keep to same concept for the numberArray, but I'm stuck on what to do differently.

Any help would be appreciated.

Thanks!

[r035198x]

1.) Test for null using if(value == null). Don't derefence a variable if you think it could be null.
2.) No need to put that ? after Int32.
3.) Get a C# tutorial and read it.

[Plater]

This does not appear to have anything to do with ArrayList, so much as it does with the misunderstanding of converting values. Upon confirmation I will change the thread title.
You should be using the Parse()/TryParse() functions, not the convert functions.
Int32.TryParse() should be usefull to you.

Int32 mynum=0;
 
bool result = Int32.TryParse(Console.ReadLine(), out mynum);
 
if (result)
{//mynum contains a valid number
}
else
{// Console.ReadLine() produced a string that was either blank ("") or could not be converted to a number
}
 

[sigil]

Also I would not use ArrayList, instead use List<string> or List<int> then you don't have to be casting all the time.

Best way I feel to do validation is to use Regex, in the long run it saves you time.

[dhyder]

Thank you everyone for the input and replies. I will definitely look into everything and see what I can get to work.

Plater, I haven't used Parse and TryParse before, but I've seen it quite a bit and is definitely something I will research.

sigil, I never thought of generics. Thanks for the idea.

[dhyder]

Plater, the TryParse is exactly what I was looking for. Works great. Thanks alot.

Thank you everyone for your help, much appreciated.