Question

I’m querying the Google Books API, and I’m parsing the books into a custom object like this:

foreach (JToken item in items)
{
    try
    {
        FoundBookViewModel viewModel = new FoundBookViewModel
        {
            Title = item.SelectToken("volumeInfo.title").ToString(),
            Isbn13 = item.SelectToken("volumeInfo.industryIdentifiers[1].identifier").ToString(),
            Authors = item.SelectToken("volumeInfo.authors").Select(x => x.ToString()).ToList().Aggregate((i, j) => i + ", " + j),
            Pages = item.SelectToken("volumeInfo.pageCount").ToString(),
            ImageUri = item.SelectToken("volumeInfo.imageLinks.smallThumbnail").ToString()
        };

        newList.Add(viewModel);
    }
    catch (Exception)
    {
        newList.Add(new FoundBookViewModel());
    }
}

However, sometimes not all data is available. Sometimes there is no ‘pageCount’, sometimes there is no ‘ISBN13’, etc. In those cases an exception is thrown at the ToString() part.

So what I want is this: when an exception is thrown for one of the properties, I just want it to be an empty string. But I don’t know a clean way to accomplish this.

I tried multiple things:

• I wrapped the whole thing inside a try catch, but then I don’t know what property was empty, so I can’t ‘fill’ it with an empty string.
• I tried using safe casting (‘as string’) but that operation is not available on SelectToken().
• Couple of other things that didn’t work anyway.

Of course I could put every operation inside its own try catch, but that will result in 5 try catch blocks in this situation, so that’s not what I’m looking for.

Who knows a clean way to solve this? Btw. I choose to use LINQ to JSON instead of materializing it directly because the Google Books API doesn’t neatly map to simple entities (the JSON contains lots of nesting).

Answer 1

If you don’t want to throw exception – don’t…

I.e. you can change item.SelectToken("volumeInfo.pageCount").ToString() into:

item.SelectToken("volumeInfo.pageCount") == null? 
   String.Empty : item.SelectToken("volumeInfo.pageCount").ToString()