LINQ query which converts XML document to object list causing exception

Question

I have a pretty large LINQ query which reads XML nodes into object properties, however a line in my query is causing a System.FormatException exception based on "Input string not in a correct format".

DeliveryFee = x.Descendants("LineItemShipping").Select(e => (double)e.Element("TotalPrice")).FirstOrDefault(),

(double)e.Element("TotalPrice") // this text in the line is highlighted by the debugger so this element must be the cause

There is 1000's of records in the XML document so I am having trouble locating the record causing the exception, is there a way I can "throw" the value causing the error to a catch() statement? I'm not exactly sure how to debug a LINQ query to get the value at runtime and I'm sure it's just an issue where that XML node is empty for this specific record. (or contains an illegal character)

I know it's a specific record as I can pull many rows without an issue however when I try to pull a specific subset that's when I get the exception, so I know it is localized to a months worth of data but I am unable to narrow it down more.

You could just run `DeliveryFee = x.Descendants("LineItemShipping").Where(e => (double?)e.Element("TotalPrice") == null).FirstOrDefault(),` — MarcinJuraszek, Jan 20 '15 at 04:19

score 2 · Accepted Answer · answered Jan 20 '15 at 04:58

To find this bug, first enable breaking when an exception is thrown in visual studio, via Debug -> Exceptions. Either enable breaking on all exceptions, or enable breaking on System.FormatException.

Now Visual Studio will stop when an exception is thrown for a LineItemShippingnode with an invalid TotalPrice. Then, in the immediate window, you can use the AncestorsAndSelf() method to find the problematic node by typing:

e.Element("SomeStatus").AncestorsAndSelf().ToArray()

Visual Studio will show you the path of XElement's that generate the exception. This should allow you to find the problematic XML node.

This helped me track down the record causing the issue. Thanks for your help! — Aaron McKelvie, Jan 20 '15 at 05:47

score 1 · Answer 2 · answered Jan 20 '15 at 04:54

You can add a try catch statement to the select expression, something like this:

    var DeliveryFee = x.Descendants("LineItemShipping").
        Select(e => {
            try
            {
                var item = (double)e.Element("TotalPrice");  
                return item;
            }
            catch(Exception ex)
            {
                //This is just so it will compile and have a return value                        
                return double.MinValue;
            }                  
        }).
        FirstOrDefault();

score 0 · Answer 3 · answered Jan 20 '15 at 05:17

0

Try changing (double) to (double?) to handle empty cases and a ?? 0 to convert nulls to zero:

(double)(x.Descendants("LineItemShipping")
          .Select(e => (double?)e.Element("TotalPrice")).FirstOrDefault()) 
          ?? 0)

answered Jan 20 '15 at 05:17

Chuck Savage

11,775
6
49
69

LINQ query which converts XML document to object list causing exception

3 Answers3