The System.Configuration.SettingsBase.Save method automatically determines whether properties that are made up of primitive types, strings, or DateTime objects have been changed, by checking the System.Configuration.SettingsPropertyValue.IsDirty property value for each System.Configuration.SettingsPropertyValue in the user profile. The System.Configuration.SettingsBase.Save method cannot explicitly determine whether a custom class has changed. You can use the ProfileModule.ProfileAutoSaving event to determine whether a custom object has been modified and then either continue with the automatic save if the object has been modified or cancel the automatic save if the object has not been modified.

To cancel the automatic profile save operation, set the ProfileAutoSaveEventArgs.ContinueWithProfileAutoSave property to false in the ProfileModule.ProfileAutoSaving event; otherwise, set the ProfileAutoSaveEventArgs.ContinueWithProfileAutoSave property to true.

There may be multiple subscribers to the ProfileModule.ProfileAutoSaving event. The System.Web.Profile.ProfileModule will use the last value that the ProfileAutoSaveEventArgs.ContinueWithProfileAutoSave property is set to. As a result, it is recommended that you explicitly set the ProfileAutoSaveEventArgs.ContinueWithProfileAutoSave property in the ProfileModule.ProfileAutoSaving event whether you are canceling or continuing with the automatic save, as you may need to overwrite the value set by an earlier subscriber.