Actually, very little.
It is true that VB.NET uses XML in a variety of ways. The new project file format is XML. The application configuration file format is XML. SOAP messages (an RPC protocol replacing DCOM) are XML. But you could lead a happy life as a VB.NET programmer without ever needing to LOOK at any of these items. And even if you had to, the first two items use such a simple format that someone could figure it out without knowing XML even existed.
However, knowledge is power. So, I recommend learning the fundamentals of XML: elements, attributes, and the concept of schemas. ADO.NET also leverages XML. If ADO.NET is in your future, then you want to look into XPath. This is the XML equivalent of SQL. In other words, it?s the syntax used to search an XML document for data.
This was first published in March 2001