Calling method from catch method doesn't work

Question

I'm trying to call a method from a catch block but the xmlnode inside the method doesn't seem to work. I'm getting a null. If I call the same method from the try block it works.

var doc = new XmlDocument();

try
{

 doc.Load(f.FullPath);
// do some work 

}

 catch (Exception e)
 {
  if (e is XMLException)
  {
   checkXML(ref doc);
  }

public void checkXML(ref XmlDocument doc)
            {

                XmlNode xn = doc.SelectSingleNode("/BroadcastMonitor/Current");
                xn["name1"].InnerText = SecurityElement.Escape(xn["name1"].InnerText);
                xn["name2"].InnerText = SecurityElement.Escape(xn["name2"].InnerText); ;


            }

Now when the catch block calls method 'checkXML', i get xn as null. But if I execute the same from the 'try' block just to check, 'xn' has a value. 'doc' too has a value regardless of when called try or from catch block.

Why is this happening? Please help me understand.

EDIT

<BroadcastMonitor>
<updated>2014-10-17T07:56:30</updated>
<Name>TESTING</Name>
<Current>

    <artistName>اصاله&  نصرى</artistName>
    <albumName>شخصيه عنيده</albumName>
    <CategoryName>ARABIC & SONGS</CategoryName>

</Current>
</BroadcastMonitor>

Thank you.

Answer 1

Your xml contains an & character which is not a 'valid' xml character and must be escaped.

<CategoryName>ARABIC & SONGS</CategoryName>

So it's causing your Load() method to throw the exception.

What you should do is escape all the invalid characters in your xml string before passing them on to an xml parser like so

yourXmlString = XmlConvert.EncodeName(yourXmlString);

You can then pass the yourXmlString on to the parser like so

var xDoc = XDocument.Parse(yourXmlString);

or if you don't want to or can't use the XDocument class you will need to make sure you save the xml encoded so that the Load() method of the XmlDocument class will be reading a file that is properly encoded.

Note that XmlDocument and XDocument classes are not the same thing and have some significant differences. Method Parse(), if I remember correctly, is one of the advantages that XDocument has over XmlDocument.

EDIT :

You can read the xml file into a string using the File class

var yourXmlString = File.ReadAllText(filePath);

Answer 2

XmlDocument is a reference type... no need to pass it with ref.

And my guess is that its failing to load in the first place so doc is really null

Answer 3

It looks like this document is missing its xml declaration tag.

try:

XmlDocument doc = new XmlDocument;
using(StreamReader reader = new StreamReader(f.FullPath))
{
    doc.LoadXml(reader.ReadToEnd());
}

Answer 4

You can use System.IO.File.ReadAllText() to get all text from file into a string variable :

string invalidXml = System.IO.File.ReadAllText(f.FullPath);

For this particular XML, you can simply replace & with it's encoded version & to make a valid XML string :

string validXml = invalidXml.Replace("&", "&");
doc.LoadXml(validXml);
.....

Related question for reference : Reading XML with an "&" into C# XMLDocument Object

Answer 5

This would be my solution:

    private static Regex InnerValues = new Regex(@"(?<=<(.*?>)).*?(?=</\1)",RegexOptions.Compiled);

    private static XmlDocument LoadInvalidDocument(string path)
    {
        XmlDocument result = new XmlDocument();
        string content = File.ReadAllText(path);

        var matches = InnerValues.Matches(content);
        foreach (Match match in matches)
        {
            content = content.Replace(match.Value,  HttpUtility.HtmlEncode(match.Value));
        }
        result.LoadXml(content);
        return result;
    }