Examples of errors detected by the V3019 diagnostic

V3019. It is possible that an incorrect variable is compared with null after type conversion using 'as' keyword.

AWS SDK for .NET

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'coreSTSClient', 'samlCoreSTSClient'. FederatedAWSCredentials.cs 219

private CredentialsRefreshState Authenticate(ICredentials userCredential)
{
  ....
  ICoreAmazonSTS coreSTSClient = ....;

  var samlCoreSTSClient
#if NETSTANDARD
    = coreSTSClient as ICoreAmazonSTS_SAML;
  if (coreSTSClient == null)                 // <=
  {
    throw new NotImplementedException(
      "The currently loaded version of AWSSDK.SecurityToken
       doesn't support SAML authentication.");
  }
#else
    = coreSTSClient;
#endif

  ....
}

Unity C# reference source code

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'targetItem', 'hierarchyTargetItem'. AssetOrGameObjectTreeViewDragging.cs 153

public override DragAndDropVisualMode DoDrag(....)
{
  var hierarchyTargetItem = targetItem as GameObjectTreeViewItem;

  if (m_CustomDragHandling != null)
  {
    DragAndDropVisualMode dragResult =
      m_CustomDragHandling(parentItem as GameObjectTreeViewItem,
                           hierarchyTargetItem,
                           ....);
    ....
  }
  DragAndDropVisualMode dragSceneResult =
    DoDragScenes(parentItem as GameObjectTreeViewItem,
                 hierarchyTargetItem,
                 ....);

  if (   targetItem != null
      && !IsDropTargetUserModifiable(hierarchyTargetItem, dropPos)) // <=
  {
    return DragAndDropVisualMode.Rejected;
  }
  ....
}

QuantConnect Lean

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'buyingPowerModel', 'futureMarginModel'. BasicTemplateFuturesAlgorithm.cs 105

public override void OnEndOfAlgorithm()
{
  var buyingPowerModel = Securities[_contractSymbol].BuyingPowerModel;
  var futureMarginModel = buyingPowerModel as FutureMarginModel;
  if (buyingPowerModel == null)
  {
    throw new Exception($"Invalid buying power model. " +
                        $"Found: {buyingPowerModel.GetType().Name}. " +
                        $"Expected: {nameof(FutureMarginModel)}");
  }
  ....
}

Telerik UI for UWP

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'dragDropElement', 'uiDragDropElement'. DragDrop.cs 91

internal static void StartDrag(....)
{
  var dragDropElement = sender as IDragDropElement;
  ....
  UIElement uiDragDropElement = dragDropElement as UIElement;
  ....
  if (dragDropElement == null ||
      !dragDropElement.CanStartDrag(trigger, initializeContext))
  {
    return;
  }
  ....
  var relativeStartDragPosition = e.GetCurrentPoint(uiDragDropElement).Position;
  var dragPositionMode = DragDrop.GetDragPositionMode(uiDragDropElement);
  ....
}

Unity C# reference source code

V3019 CWE-697 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'obj', 'newResolution'. GameViewSizesMenuItemProvider.cs 104

private static GameViewSize CastToGameViewSize(object obj)
{
  GameViewSize newResolution = obj as GameViewSize;
  if (obj == null)
  {
    Debug.LogError("Incorrect input");
    return null;
  }
  return newResolution;
}

Logify Alert Clients

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'sender', 'source'. BreadcrumbsRecorder.cs 86

void KeyDown(object sender, KeyEventArgs e) {
  FrameworkElement source = sender as FrameworkElement;
  if(!IsActive || (sender == null))
      return;
  Dictionary<string, string> properties =
    CollectCommonProperties(source, e);
  LogKeyboard(properties, e, false,
           CheckPasswordElement(e.OriginalSource as UIElement));
}

Similar errors can be found in some other places:

• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'sender', 'source'. BreadcrumbsRecorder.cs 94
• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'sender', 'source'. BreadcrumbsRecorder.cs 102
• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'sender', 'source'. BreadcrumbsRecorder.cs 110
• And 2 additional diagnostic messages.

PascalABC.NET

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'baseScope', 'this.baseScope'. CodeCompletion SymTable.cs 3497

public TypeScope(...., SymScope baseScope)
{
  ....
  this.baseScope = baseScope as TypeScope;
  ....
  if (baseScope == null)
  {
    ....
  }
  ....
}

Similar errors can be found in some other places:

• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'returned_scope', 'ts'. CodeCompletion ExpressionVisitor.cs 1595
• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'returned_scope', 'tmp_scope'. CodeCompletion DomSyntaxTreeVisitor.cs 1553
• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'returned_scope', 'ts.elementType'. CodeCompletion DomSyntaxTreeVisitor.cs 2815
• And 6 additional diagnostic messages.

Media Portal 2

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'obj', 'other'. EpisodeInfo.cs 560

public override bool Equals(object obj)
{
  EpisodeInfo other = obj as EpisodeInfo;
  if (obj == null) return false;
  if (TvdbId > 0 && other.TvdbId > 0)
    return TvdbId == other.TvdbId;
  ....
}

PowerShell

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'j', 'child'. System.Management.Automation Job.cs 1876

internal List<Job> GetJobsForComputer(String computerName)
{
  ....
  foreach (Job j in ChildJobs)
  {
    PSRemotingChildJob child = j as PSRemotingChildJob;
    if (j == null) continue;
    if (String.Equals(child.Runspace
                           .ConnectionInfo
                           .ComputerName,
                      computerName,
                      StringComparison.OrdinalIgnoreCase))
    {
      returnJobList.Add(child);
    }
  }
  return returnJobList;
}

Similar errors can be found in some other places:

• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'j', 'child'. System.Management.Automation Job.cs 1900
• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'j', 'child'. System.Management.Automation Job.cs 1923

Microsoft Bot Builder

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'step', 'prop'. FieldReflector.cs 231

protected Type StepType(object step)
{
  var field = step as FieldInfo;
  var prop = step as PropertyInfo;
  return (step == null ? null :
         (field == null ? prop.PropertyType :  // <=
                          field.FieldType));
}

Mono

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'v1', 'cmp'. Array.cs 1487

static bool QSortArrange (.... ref object v0, int hi,
                          ref object v1, ....)
{
  IComparable cmp;
  ....
  cmp = v1 as IComparable;

  if (v1 == null || cmp.CompareTo (v0) < 0) {
    ....
  }
  ....
}

Mono

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'o', 'umc'. UrlMembershipCondition.cs 111

public override bool Equals (object o)
{
  UrlMembershipCondition umc = (o as UrlMembershipCondition);
  if (o == null)                                      // <=
    return false;

  ....

  return (String.Compare (u, 0, umc.Url, ....) == 0); // <=
}

MSBuild

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'obj', 'name'. AssemblyRemapping.cs 64

public override bool Equals(object obj)
{
   AssemblyNameExtension name = obj as AssemblyNameExtension;
   if (obj == null)  // <=
   {
     return false;
   }
   ....
}

FlashDevelop

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'item', 'val'. WizardHelper.cs 67

public static void SetControlValue(....)
{
  ....
  string val = item as string;
  if (item == null) continue;
  ....
}

Old NASA World Wind (C#)

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'obj', 'robj'. RenderableObject.cs 199

public int CompareTo(object obj)
{
  RenderableObject robj = obj as RenderableObject;
  if(obj == null)   // <=
    return 1;
  return this.m_renderPriority.CompareTo(robj.RenderPriority);
}

Space Engineers

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'item', 'actionsItem'. Sandbox.Game MyGuiControlToolbar.cs 511

private void contextMenu_ItemClicked(....)
{
  ....
  var actionsItem = item as MyToolbarItemActions;
  if (item != null)                                       // <=
  {
    if (idx < 0 || idx >= actionsItem
                          .PossibleActions(ShownToolbar
                                             .ToolbarType)
                          .Count)
      RemoveToolbarItem(slot);
  ....
  }
  ....
}

Similar errors can be found in some other places:

• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'ob', 'objectBuilder'. Sandbox.Game MyBlockNavigationDefinition.cs 172
• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'Owner', 'character'. Sandbox.Game MyWelder.cs 232

Space Engineers

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'builder', 'ob'. Sandbox.Game MyWeaponBlockDefinition.cs 21

protected override void Init(
                         MyObjectBuilder_DefinitionBase builder)
{
  base.Init(builder);

  var ob = builder as MyObjectBuilder_WeaponBlockDefinition;
  Debug.Assert(builder != null);                           // <=

  WeaponDefinitionId = new MyDefinitionId(
                         ob.WeaponDefinitionId.Type,
                         ob.WeaponDefinitionId.Subtype);
  ResourceSinkGroup = MyStringHash.GetOrCompute(
                        ob.ResourceSinkGroup);
  InventoryMaxVolume = ob.InventoryMaxVolume;
}

Sony ATF

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'd', 'box'. Atf.Gui.Wpf.vs2010 PasswordBoxBehavior.cs 38

private static void OnBoundPasswordChanged(DependencyObject d,
                      DependencyPropertyChangedEventArgs e)
{
    PasswordBox box = d as PasswordBox;

    if (d == null || !GetBindPassword(d))
    {
        return;
    }

    box.PasswordChanged -= HandlePasswordChanged;
    ....
}

.NET Compiler Platform ("Roslyn")

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'parentStartTag', 'parentElement'. XmlTagCompletionCommandHandler.cs 123

private bool HasMatchingEndTag(
  XmlElementStartTagSyntax parentStartTag)
{
  if (parentStartTag == null)
  {
    return false;
  }

  var parentElement = parentStartTag.Parent as XmlElementSyntax;
  if (parentStartTag == null)
  {
    return false;
  }
  var endTag = parentElement.EndTag;
  ....
}

This error can also be detected in a different way. The analyzer generates such a message for this code fragment: V3021 There are two 'if' statements with identical conditional expressions. The first 'if' statement contains method return. This means that the second 'if' statement is senseless XmlTagCompletionCommandHandler.cs 117

.NET Compiler Platform ("Roslyn")

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'other', 'otherResourceString'. LocalizableResourceString.cs 121

protected override bool AreEqual(object other)
{
  var otherResourceString = other as LocalizableResourceString;
  return
    other != null &&
    _nameOfLocalizableResource ==
      otherResourceString._nameOfLocalizableResource &&
    _resourceManager == otherResourceString._resourceManager &&
    _resourceSource == otherResourceString._resourceSource &&
    ....
}

.NET Compiler Platform ("Roslyn")

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'obj', 'd'. DiagnosticDescription.cs 201

public override bool Equals(object obj)
{
  var d = obj as DiagnosticDescription;

  if (obj == null)
    return false;

  if (!_code.Equals(d._code))
    return false;
  ....
}

IronPython and IronRuby

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'node', 'scalar'. RubyConstructor.cs 230

private static RubyRegex/*!*/ ConstructRubyRegexp(
  RubyConstructor/*!*/ ctor, Node/*!*/ node) {
  ScalarNode scalar = node as ScalarNode;
  if (node == null) {
    throw RubyExceptions.CreateTypeError(
      "Can only create regex from scalar node");
  }
  Match match = _regexPattern.Match(scalar.Value);
  ....
}

IronPython and IronRuby

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'value', 'strValue'. EnvironmentSingletonOps.cs 189

public static bool HasValue(RubyContext/*!*/ context,
  object/*!*/ self, object value) {
  var strValue = value as MutableString;
  if (value == null) {
    return false;
  }
  var clrStrValue = strValue.ConvertToString();
  ....
}

MonoDevelop

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'sender', 'selection'. MonoDevelop.Ide TasksOptionsPanel.cs 123

void OnTokenSelectionChanged (object sender, EventArgs args)
{
  TreeSelection selection = sender as TreeSelection;
  if (sender != null)
  {
    TreeIter iter;
    TreeModel model = (TreeModel)tokensStore;
    if (selection.GetSelected (out model, out iter)) {
        entryToken.Text = (string)tokensStore.GetValue (iter, 0);
        comboPriority.Active = (int)tokensStore
                                      .GetValue (iter, 1);
    } else
    {
      entryToken.Text = String.Empty;
      comboPriority.Active = (int)TaskPriority.Normal;
    }
  }
}

Similar errors can be found in some other places:

• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'data', 'urlMarker'. MonoDevelop.SourceEditor MarkerOperationsHandler.cs 43
• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'symbol', 'method'. CSharpBinding FormatStringHelper.cs 59

MonoDevelop

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'o', 'sr'. MonoDevelop.Core SolutionItemReference.cs 81

public override bool Equals (object o)
{
  SolutionItemReference sr = o as SolutionItemReference;
  if (o == null)
    return false;
  return (path == sr.path) && (id == sr.id);
}

.NET Core Libraries (CoreFX)

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'comparand', 'comparedCredentialKey'. CredentialCache.cs 4007

public override bool Equals(object comparand)
{
  CredentialHostKey comparedCredentialKey =
                                  comparand as CredentialHostKey;

  if (comparand == null)
  {
    // This covers also the compared == null case
    return false;
  }

  bool equals = string.Equals(AuthenticationType,
        comparedCredentialKey.AuthenticationType, ....
  ....
}

Similar errors can be found in some other places:

• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'comparand', 'comparedCredentialKey'. CredentialCache.cs 497
• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'myObject', 'myString'. CaseInsensitiveAscii.cs 46
• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'a', 'nodeA'. AttributeSortOrder.cs 22
• And 3 additional diagnostic messages.

Microsoft Code Contracts

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'other', 'right'. CallerInvariant.cs 189

public override Predicate JoinWith(Predicate other)
{
  var right = other as PredicateNullness;
  if (other != null)
  {
    if (this.value == right.value)
    {
      return this;
    }
  }

  return PredicateTop.Value;
}

Similar errors can be found in some other places:

• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'facts', 'moreRefinedFacts'. SimplePostconditionDispatcher.cs 319
• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'objProvenance', 'provenance'. AssertionCrawlerAnalysis.cs 816
• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'prev', 'other'. NonRelationalValueAbstraction.cs 1063
• And 7 additional diagnostic messages.

SharpDevelop

V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'node', 'solutionFolderNode'. SolutionNodeCommands.cs 127

public override void Run()
{
  ....
  ISolutionFolderNode solutionFolderNode =
    node as ISolutionFolderNode;

  if (node != null)
  {
    ISolutionFolder newSolutionFolder =
      solutionFolderNode.Folder.CreateFolder(....);
    solutionFolderNode.Solution.Save();
  ....
}

Similar errors can be found in some other places:

• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'geometry', 'g'. PathHandlerExtension.cs 578
• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'oldTransform', 'tg'. ModelTools.cs 420
• V3019 Possibly an incorrect variable is compared to null after type conversion using 'as' keyword. Check variables 'node', 'solutionFolderNode'. SolutionNodeCommands.cs 104