Returns the index of the new message that raised the event. You can pass this to SmsDevice.GetMessageAsync to retrieve the new message itself.
Note This functionality is only available to mobile operator apps and Windows Store apps given privileged access by mobile network operators, mobile broadband adapter IHV, or OEM. For more information, see Mobile Broadband: Windows Store device apps.
Note Note that this class and its methods are supported for the maintenance of legacy desktop apps that used it in earlier versions of Windows; and if you do use this class, you must specify the Windows.Devices.Sms.LegacySmsApiContract in your app's manifest. Do not use this class if you are developing new apps for Windows 10. Instead, use the members of this namespace that do not require the Windows.Devices.Sms.LegacySmsApiContract.