How do I convert a String into a XML in vb.net

You can use different approaches offered by .NET FCL. Here is my short overview of them:

1. Use System.Xml.XmlDocument class. It implements DOM interface; this way is the easiest and good enough if the size if the document is not too big.
   See http://msdn.microsoft.com/en-us/library/system.xml.xmldocument.aspx[^].
2. Use the class System.Xml.XmlTextReader; this is the fastest way of reading, especially is you need to skip some data.
   See http://msdn.microsoft.com/en-us/library/system.xml.xmlreader.aspx[^].
3. Use the class System.Xml.Linq.XDocument; this is the most adequate way similar to that of XmlDocument, supporting LINQ to XML Programming.
   See http://msdn.microsoft.com/en-us/library/system.xml.xmldocument.aspx[^], http://msdn.microsoft.com/en-us/library/bb387063.aspx[^].

Besides, not in all cases you have to work with XML directly. In many cases, you can use serialization
http://en.wikipedia.org/wiki/Serialization[^],
https://msdn.microsoft.com/en-us/library/7ay27kt9%28v=vs.110%29.aspx[^].

In particular, you could use DataContract: https://msdn.microsoft.com/en-us/library/ms733127%28v=vs.110%29.aspx[^].

—SA