Examples of errors detected by the V3042 diagnostic

V3042. Possible NullReferenceException. The '?.' and '.' operators are used for accessing members of the same object.

Xamarin.Forms

V3042 Possible NullReferenceException. The '?.' and '.' operators are used for accessing members of the Element object Xamarin.Forms.Platform.WinRT MasterDetailPageRenderer.cs 288

void UpdateTitle()
{
  if (Element?.Detail == null)
    return;

   ((ITitleProvider)this).Title =
     (Element.Detail as NavigationPage)
       ?.CurrentPage?.Title ?? Element.Title
                            ?? Element?.Title;
}

.NET Core Libraries (CoreFX)

V3042 Possible NullReferenceException. The '?.' and '.' operators are used for accessing members of the 'sym' object SymbolStore.cs 56

private static void InsertChildNoGrow(Symbol child)
{
  ....
  while (sym?.nextSameName != null)
  {
    sym = sym.nextSameName;
  }

  Debug.Assert(sym != null && sym.nextSameName == null);
  sym.nextSameName = child; // <=
  ....
}

.NET Core Libraries (CoreFX)

V3042 Possible NullReferenceException. The '?.' and '.' operators are used for accessing members of the 'property' object JsonClassInfo.AddProperty.cs 179

internal JsonPropertyInfo CreatePolymorphicProperty(....)
{
  JsonPropertyInfo runtimeProperty
    = CreateProperty(property.DeclaredPropertyType,    // <=
                     runtimePropertyType,
                     property.ImplementedPropertyType, // <=
                     property?.PropertyInfo,           // <=
                     Type,
                     options);
  ....
}

Azure PowerShell

V3042 Possible NullReferenceException. The '?.' and '.' operators are used for accessing members of the 'imageAndOsType' object VirtualMachineScaleSetStrategy.cs 81

internal static ResourceConfig<VirtualMachineScaleSet>
CreateVirtualMachineScaleSetConfig(...., ImageAndOsType imageAndOsType, ....)
{
  ....
  VirtualMachineProfile = new VirtualMachineScaleSetVMProfile
  {
    OsProfile = new VirtualMachineScaleSetOSProfile
    {
        ....,
        WindowsConfiguration =
          imageAndOsType.CreateWindowsConfiguration(),  // <=
        ....,
    },
    StorageProfile = new VirtualMachineScaleSetStorageProfile
    {
        ImageReference = imageAndOsType?.Image,  // <=
        DataDisks = DataDiskStrategy.CreateVmssDataDisks(
          imageAndOsType?.DataDiskLuns, dataDisks)  // <=
    },
  },
  ....
}

Azure PowerShell

V3042 Possible NullReferenceException. The '?.' and '.' operators are used for accessing members of the 'existingContacts' object RemoveAzureKeyVaultCertificateContact.cs 123

public override void ExecuteCmdlet()
{
  ....
  List<PSKeyVaultCertificateContact> existingContacts;

  try
  {
    existingContacts = this.DataServiceClient.
                       GetCertificateContacts(VaultName)?.ToList();
  }
  catch (KeyVaultErrorException exception)
  {
    ....
    existingContacts = null;
  }

  foreach (var email in EmailAddress)
  {
    existingContacts.RemoveAll(....);  // <=
  }
  ....
}

osu!

V3042 [CWE-476] Possible NullReferenceException. The '?.' and '.' operators are used for accessing members of the 'val.NewValue' object TournamentTeam.cs 41

public TournamentTeam()
{
  Acronym.ValueChanged += val =>
  {
    if (....)
      FlagName.Value = val.NewValue.Length >= 2     // <=
        ? val.NewValue?.Substring(0, 2).ToUpper()
        : string.Empty;
  };
  ....
}

Similar errors can be found in some other places:

• V3042 [CWE-476] Possible NullReferenceException. The '?.' and '.' operators are used for accessing members of the 'val.NewValue' object TournamentTeam.cs 48

osu!

V3042 [CWE-476] Possible NullReferenceException. The '?.' and '.' operators are used for accessing members of the 'api' object SetupScreen.cs 77

private void reload()
{
  ....
  new ActionableInfo
  {
    Label = "Current User",
    ButtonText = "Change Login",
    Action = () =>
    {
      api.Logout();     // <=
      ....
    },
    Value = api?.LocalUser.Value.Username,
    ....
  },
  ....
}