Using LINQ to Easily Serialize an Exception to XML

I was working on my capstone project last semester, and ran into a need to log exception data to a portable format. I loves me some XML, so that was my obvious (and, let's be honest, only) choice. .NET includes a lot of built-in code in most data types to allow for seamless serialization, so I thought this would be a simple matter.

Nope.

Turns out the Exception class in .NET contains an IDictionary member, Data, that contains some extra information that the developer might find useful. The problem? IDictionary does not implement ISerializable, which is required since it is not a primitive type. So, when I attempt to "lazy" serialize the Exception object, the runtime hits the Data member and throws an exception.

Drat.

Since I really did not want to have to write some complicated wrapper class (I was a bit pressed for time by this point in the semester), I turned to my trusty friend Google to see how other people had handled this problem. It took a bit of searching, but eventually I found a perfect solution to my problem here: http://seattlesoftware.wordpress.com/2008/08/22/serializing-exceptions-to-xml/

The solution is remarkably simple: extend the XElement class in LINQ. I mean, this is "duh" simple. Once you create the extended class, logging an exception is a simple as this:

XDocument log = XDocument.Load( path_to_file );
log.Root.Add( new ExceptionXElement( ex ) );
log.Save( path_to_file );

Here's the code as implemented:

using System;
using System.Collections;
using System.Linq;
using System.Xml.Linq;

/// <summary>Represent an Exception as XML data.</summary>
public class ExceptionXElement : XElement
{
    /// <summary>Create an instance of ExceptionXElement.</summary>
    /// <param name="exception">The Exception to serialize.</param>
    public ExceptionXElement(Exception exception)
        : this(exception, false)
    { ; }

    /// <summary>Create an instance of ExceptionXElement.</summary>
    /// <param name="exception">The Exception to serialize.</param>
    /// <param name="omitStackTrace">
    /// Whether or not to serialize the Exception.StackTrace member
    /// if it's not null.
    /// </param>
    public ExceptionXElement(Exception exception, bool omitStackTrace)
        : base(new Func<XElement>(() =>
        {
            // Validate arguments
            if (exception == null)
            {
                throw new ArgumentNullException("exception");
            }
        
            // The root element is the Exception's type
        
            XElement root = new XElement(exception.GetType().ToString());
        
            if (exception.Message != null)
	    {
	        root.Add(new XElement("Message", exception.Message));
	    }
        
            // StackTrace can be null, e.g.:
            // new ExceptionAsXml(new Exception())
            if (!omitStackTrace &amp;&amp; exception.StackTrace != null)
	    {
	        vroot.Add(
	            new XElement("StackTrace",
	                from frame in exception.StackTrace.Split('\n')
	    	        let prettierFrame = frame.Substring(6).Trim()
	    	        select new XElement("Frame", prettierFrame))
                );
            }
        
	    // Data is never null; it's empty if there is no data
	    if (exception.Data.Count > 0)
	    {
	        root.Add(
                    new XElement("Data",
	    	        from entry in exception.Data.Cast<DictionaryEntry>()
	                let key = entry.Key.ToString()
	    	        let value = (entry.Value == null) ? "null" : entry.Value.ToString()
	    	        select new XElement(key, value))
	    	);
	    }
        
            // Add the InnerException if it exists
	    if (exception.InnerException != null)
	    {
	        root.Add(new ExceptionXElement(exception.InnerException, omitStackTrace));
	    }
        
	    return root;
        })())
    { ; }
}

Enjoy!

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