XML field replacement in C#

Question

ok, so, i have an xml file that looks like this:

<?xml version="1.0"?>
<Users>
  <User ID="1">
    <nickname>Tom</nickname>
    <password>a password</password>
    <host>[email protected]</host>
    <email>anemail</email>
    <isloggedin>false</isloggedin>
    <permission>10</permission>
  </User>
  <User ID="2">
    <nickname>ohai</nickname>
    <password>sercret</password>
    <host>my@host</host>
    <email>my@email</email>
    <isloggedin>false</isloggedin>
    <permission>1</permission>
  </User>
<Users>

now, first, i will have a return of what their ID number is, so, ill have "2". from that, i will need to go into, and edit the fields in it, and resave the xml. so basically what i need, is to open the file, find the info for User ID="2", and resave the xml, with DIFFERENT values inside of user 2, without affecting the rest of the document.

examlpe:

  <User ID="2">
    <nickname>ohai</nickname>
    <password>sercret</password>
    <host>my@host</host>
    <email>my@email</email>
    <isloggedin>false</isloggedin>
    <permission>1</permission>
  </User>

//do the alterations here, and end up with

  <User ID="2">
    <nickname>ohai</nickname>
    <password>somthing that is different than before</password>
    <host>the most current host that they were seen as</host>
    <email>my@email</email>
    <isloggedin>false</isloggedin>
    <permission>1</permission>
  </User>

etc.

Summary: i need to open a text file, return the information via ID number, edit the information, re-save the file. without affecting anything other than user 2

~Thanks!

Answer 1

There are multiple ways you could do this - this is with an XmlDocument, which works in .NET 1.x and up, and works fine as long as your XML document isn't too long:

// create new XmlDocument and load file
XmlDocument xdoc = new XmlDocument();
xdoc.Load("YourFileName.xml");

// find a <User> node with attribute ID=2
XmlNode userNo2 = xdoc.SelectSingleNode("//User[@ID='2']");

// if found, begin manipulation    
if(userNo2 != null)
{
   // find the <password> node for the user
   XmlNode password = userNo2.SelectSingleNode("password");
   if(password != null)
   {
      // change contents for <password> node 
      password.InnerText = "somthing that is different than before";
   }

   // find the <host> node for the user
   XmlNode hostNode = userNo2.SelectSingleNode("host");
   if(hostNode != null)
   {
      // change contents for <host> node 
      hostNode.InnerText = "the most current host that they were seen as";
   }

   // save changes to a new file (or the old one - up to you)
   xdoc.Save("YourFileNameNew.xml");
}

If you're using .NET 3.5 and up, you could also check into Linq-to-XML for a probably even easier way to manipulate your XML document.

Marc

Answer 2

Check out this question, should have your answer using Linq-to-XML. This involves writing out to a Console window, but the theory is the same.

http://stackoverflow.com/questions/331502/linq-to-xml-update-alter-the-nodes-of-an-xml-document

Answer 3

You may use XmlDocument for this:

var doc = new XmlDocument();
doc.Load("1.xml");
var node = doc.SelectSingleNode(@"//User[@ID='2']");
node.SelectSingleNode("password").InnerText="terces";
doc.Save("1.xml");