how to deal with exception in LINQ Select statement

Question

Hello, I have a LINQ query as follows

 m_FOO = rawcollection.Select(p=> p.Split(' ')).Select(p =>
            {
                int thing = 0;

                try
                {
                     thing = CalculationThatCanFail(p[1]);
                }
                catch{}
                return new { Test = p[0], FooThing = thing};
            })
            .GroupBy(p => p.Test)
            .ToDictionary(p => p.Key, s => s.Select(q => q.FooThing).ToList());

So, the CalculationThatCanFail throws sometimes. I don't want to put null in and then filter that out with another Where statement later, and a junk value is equally unacceptable. Does anyone know how to handle this cleanly? Thanks.

EDIT: There's a good reason for the double Select statement. This example was edited for brevity

Answer 1

For these situations I use a Maybe type (similar to this one) for calculations that may or may not return a value, instead of nulls or junk values. It would look like this:

Maybe<int> CalculationThatMayHaveAValue(string x)
{
    try
    {
        return CalculationThatCanFail(x);
    }
    catch
    {
        return Maybe<int>.None;
    }
}

 //...

 var xs = ps.Select(p =>
            {
                Maybe<int> thing = CalculationThatMayHaveAValue(p[1]);
                return new { Test = p[0], FooThing = thing};
            })
            .Where(x => x.FooThing.HasValue);

Answer 2

I'm not clear from question if you mean, you don't want to use null for FooThing or you don't want to use null for the entire anonymously typed object. In any case, would this fit the bill?

 m_FOO = rawcollection.Select(p=> p.Split(' ')).Select(p =>
        {
            int thing = 0;

            try
            {
                 thing = CalculationThatCanFail(p[1]);
                 return new { Test = p[0], FooThing = thing};
            }
            catch
            {
                return null;
            }
        })
        .Where(p => p != null)
        .GroupBy(p => p.Test)
        .ToDictionary(p => p.Key, s => s.Select(q => q.FooThing).ToList());