Hey guys C# application help needed

I don't want to give too much help either as the idea of these interviews is to show what you can do, not what other people can do. Asking intelligent questions on CP is a good start though :P. I'll give a very brief overview of how I'd approach this.

1. First find a data source. There are various trading API providers but if you just want 5 minute data and don't mind it being delayed, there are many free sources. Look for one which provides the data as a web service you can bind to from VS, if you're going for a .Net desktop app (WCF is good, REST or the older version which I can't currently remember the name of which uses SOAP as the transfer protocol is also fine), so you can auto-generate the client side stuff and not have to parse up a server response.

2. Store the prices in a business layer. Okay, they only asked you for one price, but in the real world this app would almost certainly subscribe to multiple prices so I'm going to violate the Extreme Programming 'You Ain't Gonna Need It' principle and prepare for that now. For your problem this layer is trivial:

class PriceModel {
 decimal USDGBP;
}

... but you could make it implement INotifyPropertyChanged and therefore be bindable. Your web service client should assign to this property, and the setter should notify the UI when that happens. (Again, for such a trivial case this isn't really necessary but I always start as I mean to continue.)

3. The UI should have a field which is bound to that. Either with actual data binding or a notify event handler which sets the UI field.

4. Somewhere, you need to store the previous value, so you can do change related updates. For a trivial case like this you can probably use the UI field itself as the cache (as change display is a UI related thing I don't mind this too much).

5. For logging, bind a logger to the notification event of the business layer. I'm not sure what 'application activity' means but the logger should also be available in other places where you want to log stuff.

I hope you are honest about asking for help if it is asked ;). (Heh, if I were setting these questions I think this answer is at the level where it should be helpful without actually doing the problem for you.

Below link might help you

http://www.eggheadcafe.com/community/aspnet/2/10087566/get-the-currency-value-from-a-website-to-my-local-database.aspx[^]

Typically this type of question is looking to see if you can do the basics. Does your code have intelligent exception handling in there? Does it check inputs? What about failover support (in other words what do you do when the web service isn't there)? Do you have tests in place? If it's a web application, does it do a lot of postbacks, or are you using client-side technologies to make for a more responsive application?

More importantly though, when you turn up for the next interview, can you actually walk me through your code and explain it? In other words, did you write it or have you cribbed it from some other source?