Allow the user to specify the source of the XmlHttpObject. Ex: IsUserAvailable.aspx which produces XML or plaintext.
Allow the user to specify to use an ASP.NET event to return the XmlHttpObject. Ex: TextChanged += “IsUserAvailable_TextChanged”
Must be able to return:
DataSet
DataReader
XmlReader
Scalar (object)
Must be degradable. If browser does not support XmlHttpObject, the javascript will either do nothing (no errors) or revert to server side post backs.