Exception from LINQ query not caught where expected

Question

I am parsing an input string to a class using a LINQ query. I have wrapped the query in a try/catch block to deal with parse errors. The problem is that the exception is not caught at the point at which I expect it to occur, it only stops program flow at the point at which the resulting object (parsedList) is accessed. Have I misunderstood something about how LINQ works or how exceptions work?

public class Foo
{
    public decimal Price { get; set; }
    public decimal VAT { get; set; }
}

public class MyClient
{
    public IEnumerable<Foo> ParseStringToList(string inputString)
    {
        IEnumerable<Foo> parsedList = null;
        try
        {
            string[] lines = inputString.Split(new string[] { "\n" }, StringSplitOptions.None);

            // Exception should be generated here
            parsedList =
                from line in lines
                let fields = line.Split('\t')
                where fields.Length > 1
                select new Foo()
                {
                    Price = Decimal.Parse(fields[0], CultureInfo.InvariantCulture),   //0.00
                    VAT = Decimal.Parse(fields[1], CultureInfo.InvariantCulture)    //NotADecimal (EXCEPTION EXPECTED)
                };
        }
        catch (FormatException)
        {
            Console.WriteLine("It's what we expected!");
        }

        Console.WriteLine("Huh, no error.");
        return parsedList;
    }
}

class Program
{
    static void Main(string[] args)
    {
        MyClient client = new MyClient();
        string inputString = "0.00\tNotADecimal\n";
        IEnumerable<Foo> parsedList = client.ParseStringToList(inputString);
        try
        {
            //Exception only generated here
            Console.WriteLine(parsedList.First<Foo>().Price.ToString());
        }
        catch (FormatException)
        {
            Console.WriteLine("Why would it throw the exception here and not where it fails to parse?");
        }
    }
}

Answer 1

Unless you force execution, the LINQ query is not executed until it is actually needed ("deferred execution"). It may not even be executed completely - only those parts that are needed ("lazy evaluation").

See this : https://msdn.microsoft.com/en-gb/library/mt693152.aspx and this :https://blogs.msdn.microsoft.com/ericwhite/2006/10/04/lazy-evaluation-and-in-contrast-eager-evaluation/

You can force the complete execution immediately by adding something like .ToList() or .ToArray() to the end of the Linq query.