System 2.0.0.0 4.0.0.0 System.ComponentModel.AsyncCompletedEventArgs Instances of this class are passed to the . Provides data for the event. Property 2.0.0.0 4.0.0.0 System.String To be added. You should check the and properties to determine whether the upload completed. If the property's value is an object or the property's value is true, the asynchronous operation did not complete correctly and the property's value will not be valid. Gets the server reply to a string upload operation that is started by calling an method.