StackOverflowException overriding Page in custom class

I was overriding the Page in a custom class that defined user control specific things that my app would do while being run. Each user control inherited from this UserControl class that inherited from System.Web.UI.UserControl. The problem was every time I tried to access the property, I would get a StackOverflowException. My code:


public new VolatileMinds.Web.Common.Page Page { get { return this.Page as VolatileMinds.Web.Common.Page; } }


ended up looking like this;


public new VolatileMinds.Web.Common.Page { get { return System.Web.HttpContext.Current.Handler as VolatileMinds.Web.Common.Page; } }


The problem was that it was trying to recursively cast the Page over and over again, causing the StackOverflowException. Using the Current.Handler sovles this issue.

NOTE: I don't really use absolute namespaces when doing this stuff, I thought it would be easier, however, to understand what was happening if I did.

Cannot add an entity with a key that is already in use.

I got this error today while working with Linq2Sql.

I had an object "Person".

Person person = new Person();

Person has a property called Child, but the child already exists in the database. I thought that assigning the current child in the DB to the person.Child property would just set the value for the Person and not mess with child. It doesn't quite work that way.


person.Child = dc.Childs.Where(c => c.ChildID == childID).SingleOrDefault();

dc.Persons.InsertOnSubmit(person);
dc.SubmitChanges();


The last line will fail with the aformentioned error. I ended up using the ChildID property instead (the former was the better way for the problem at hand, but setting the child ID worked after adding some additional code) so it looked like this.


person.ChildID = childID;

dc.Persons.InsertOnSubmit(person);
dc.SubmitChanges();


The reason this happens is because  you are trying to save an object that is already in the database.
Nifty.

gnump3d on Karmic

Go here: http://packages.debian.org/etch/all/gnump3d/download

download from your favorite mirror.

sudo dpkg -i gnump3d*.deb


rejoice!

Credit Card Validator in C#

I needed a credit card validator for a few of my projects. I found a few snippets of code throughout google, but nothing really just giving me what I needed, so I wanted to post my class. Maybe it will help others doing the same thing I did.

    public class CardValidator
    {
        public string CardType { get; private set; }
        public bool IsValid { get; private set; }
        public string ResultingError { get; private set; }
       
        public string CardNumber { get; set; }
        public DateTime CardExpiration { get; set; }

        public void Validate()
        {
            IsValid = false;

            if (string.IsNullOrEmpty(CardNumber))
            {
                ResultingError = "Card number empty....";
                return;
            }

            if (CardNumber.Length > 16)
            {
                ResultingError = "Card number too long";
                return;
            }

            foreach (char digit in CardNumber)
            {
                if (!char.IsDigit(digit))
                {
                    ResultingError = "Card number contains invalid characters";
                    return;
                }
            }

            if (CardExpiration < DateTime.Today)
            {
                ResultingError = "Card has expired.";
                return;
            }

            int sum = 0;
            for (int i = CardNumber.Length - 1; i >= 0; i--)
            {
                if (i % 2 == CardNumber.Length % 2)
                {
                    int n = int.Parse(CardNumber.Substring(i, 1)) * 2;
                    sum += (n / 10) + (n % 10);
                }
                else
                {
                    sum += int.Parse(CardNumber.Substring(i, 1));
                }
            }

            IsValid = (sum % 10 == 0);

            if (IsValid == true)
            {
                switch (CardNumber.Substring(0, 1))
                {
                    case "3":
                        CardType = "AMEX/Diners Club/JCB";
                        break;
                    case "4":
                        CardType = "VISA";
                        break;
                    case "5":
                        CardType = "MasterCard";
                        break;
                    case "6":
                        CardType = "Discover";
                        break;
                    default:
                        CardType = "Unknown";
                        break;
                }
            }
            else
            {
                CardType = "Invalid";
            }
        }
    }