public void WriteStartProcessingInstruction(string target) {
// Xml state transitions
ConstructWithinContent(XPathNodeType.ProcessingInstruction);
// Verify PI name
ValidateNames.ValidateNameThrow("", target, "", XPathNodeType.ProcessingInstruction, ValidateNames.Flags.AllExceptPrefixMapping);
this.piTarget = target;
this.piText = string.Empty;
this.xstate = XmlState.WithinPI;
this.depth++;
}