Turn Off DTD Validation When Processing an XML File

I've had two situtions recently where I needed to turn off DTD validation before processing an XML file in a .NET app. The ability to do so is in the class library, but there aren't a lot of examples. Here are two ways using two different objects:

XmlDocument doc = new XmlDocument();
doc.XmlResolver = null;
// or
XmlValidatingReader xmlReader = 
  new XmlValidatingReader(new XmlTextReader(openFileDialog1.FileName));
xmlReader.ValidationType = ValidationType.None;

In the second example, the user was browsing for an XML file on the network and they requested the ability to use a non-validating file for testing purposes.