Код: Выделить всё
string xmlFile = "KeePass.config.xml";
System.Xml.XmlDocument xmlDoc = new System.Xml.XmlDocument();
XmlWriterSettings settings = new XmlWriterSettings();
settings.IndentChars = "\t";
settings.Indent = true;
xmlDoc.Load(xmlFile);
xmlDoc.SelectSingleNode("Configuration/Application/LastUsedFile").InnerText = fileName;
xmlDoc.Save(xmlFile);