Question

I read somewhere that one should never use error conditions as normal program flow. Makes excellent sense to me… But

C# application sitting on top of a MySQL db. I need to parse a string value into two parts, an ID, and a value. (The original data come from a Devonian database), then validate the value against a lookup table. So, a couple of original strings might look like this:

‘6776 Purple People Eater’

‘BIK Yellow Polka-Dot Bikini (currently in use)’

‘DCP Deuce Coup’

So, my little utility parses each string into the ID and the description based on the index of the first space (fortunately, consistent). I then pass the ID to the lookup, get the new value and away we go.

Unfortunately, TPTB also decided that we no longer need no stinkin’ Yellow Polka-Dot Bikinis (currently in use). So, BIK does not return a row. Here’s a code snippet:

    foreach (string product in productTokens) {       tempProduct = product.Trim();       if (tempProduct.Length > 0) {         if (tempProduct.Length < 10) {           product_id = tempProduct;         }         else {           int charPosition = tempProduct.IndexOf(' ');           product_id = tempProduct.Substring(0, charPosition);         }         try {           s_product = productAdapter.GetProductName(product_id).ToString();         }         catch (Exception e) {           if (e.Message.ToString() == 'Object reference not set to an instance of an object.') {             s_product = '';           }           else {             errLog.WriteLine('Invalid product ID ' + e.Message.ToString());             Console.WriteLine('Invalid product ID ' + e.Message.ToString());             throw;           } //else         } //catch         if (s_product.Length > 0) {           sTemp = sTemp + s_product + '; ';         }       } //if product.length > 0     } //foreach product in productTokens 

Really, really ugly! Particularly the part where I test for an invalid IDin the catch block. There simply must be a better way to handle this.

If anyone can help me out, I’d really appreciate it.

Thanks.

Answer 1

You shouldn’t be calling ToString() at that point, first you should check if the value returned is null;

object productName = productAdapter.GetProductName(product_id); if ( productName != null ) {     s_product = productName.ToString(); } else {     s_product = String.Empty; }