Question

I have an ArrayList that comes from a json deserializer. This array should only contain numbers but as always, bad things can happen and I’m looking to avoid having to handle an exception. This is what I have:

var TheListOfLongs = (from object s in TheArrayList 
                      select Convert.ToInt64(s)).ToList<long>();

This works fine as long as TheArrayList only contains numbers. How can I change the Convert.ToInt64 statement to a TryParse?

Thanks.

Answer 1

long outValue;
//will work, but double conversion
var result = TheArrayList.Cast<object>()
            .Where(m => Int64.TryParse(m.ToString(), out outValue))
            .Select(m => Convert.ToInt64(m)).ToList();

//should avoid double Parse, but untested, see Daniel Hilgarth's answer and warnings.
var result = TheArrayList.Cast<object>()
            .Where(m => Int64.TryParse(m.ToString(), out outValue))
            .Select(m => outValue).ToList();

or good old foreach, which is probably the best choice.

var list = new List<long>();
long outValue;
foreach (object value in the ArayList) {
   if (Int64.TryParse(value.ToString(), out outValue))
      list.Add(outValue);
}