What is the “maxCharsCount” limit for System.Xml.XmlTextReaderImpl.GetChars?

In Microsoft c# Visual Studio I am using XPathNavigator to read and manipulate an XML data set. The exception that is thrown is very descriptive in pinpointing the problem with the XML file that is read. There is one text field that exceeds the limit of what is allowed for a string length. And so, I want to know what that limit is. Also, I am open to suggestions on how I can programmatically parse out the xml file before hand or during the process.