Assemblies: System.Xml (in System.Xml.dll)
System.Xml.ReaderWriter (in System.Xml.ReaderWriter.dll)
You must set this value to true when you create a new XmlWriter instance if you want to use asynchronous XmlWriter methods on that instance. After the XmlWriter instance is created, the property is read-only. The default value of this property is false.
This flag is ignored by the XmlWriter.Create overload. This means that if you create a new XmlWriter based on an existing XmlWriter, the async behavior depends on the input XmlWriter, and you cannot use the flag to change the async behavior.