Reading & Writing other application config files

I recently had to write a configuration tool to manage the configuration settings of a bunch of other programs. 
Here's a little snippet, which also shows using XPath to read XML.




using System.Xml.XPath;


private string ReadOtherAppConfigSetting(string fileName, string setting)
{
 string result = "";

 try
 {
   XmlDocument exeConfig = new XmlDocument();
   exeConfig.Load(fileName);
   XPathNavigator xNav = exeConfig.CreateNavigator();
   XPathExpression dsExpr = xNav.Compile("//configuration/appsettings/add[@key='"+setting+"']");
   XPathNodeIterator iterator = xNav.Select(dsExpr);

   if (iterator.Count == 1)
   {
     if (iterator.CurrentPosition == 0)
     {
       iterator.MoveNext();
     }

     result = iterator.Current.GetAttribute("value", "");
   }
 }
 catch {} //Don't care if can't find or doesn't exist as can default to empty string

 return result;
}

private bool WriteOtherAppConfigSetting(string fileName, string setting, string newValue)
{
 bool result = false;

 XmlDocument exeConfig = new XmlDocument();   
 XmlNode oldNode = null;

 if (File.Exists(fileName))
 {
   exeConfig.Load(fileName);

   try
   {
     oldNode = exeConfig.DocumentElement.SelectSingleNode("//configuration/appsettings/add[@key='"+setting+"']");
   }
   catch {} //old child or file may not exist
 
   //Delete existing entry (if exists)
    if (oldNode != null)
   {
     exeConfig.LastChild.FirstChild.RemoveChild(oldNode);
   }
 }
 else
 {
   //If file doesn't exist, create a basic structure
    exeConfig.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?><configuration><appsettings></appsettings></configuration>");
 }

 try
 {
   //add the new setting
    XmlElement newNode = exeConfig.CreateElement("add");
   newNode.SetAttribute("key", setting);
   newNode.SetAttribute("value", newValue);

   exeConfig.LastChild.FirstChild. AppendChild(newNode);
   exeConfig.Save(fileName);
   result = true;
 }
 catch
 {
   throw new IOException("Unable to save configuration settings. Manually edit config file or delete it and then try resaving settings.");
 }

 return result;
}