[StyleCleanUp] Addressing CS warnings Part 1

src/Microsoft.DotNet.Wpf/src/.editorconfig

@@ -182,12 +182,6 @@ dotnet_diagnostic.CA5351.severity = suggestion
 # CA5362: Potential reference cycle in deserialized object graph
 dotnet_diagnostic.CA5362.severity = suggestion
 
-# CSIsNull001: Use 'is' pattern check
-dotnet_diagnostic.CSIsNull001.severity = suggestion
-
-# CSIsNull002: Use 'is not' pattern check
-dotnet_diagnostic.CSIsNull002.severity = suggestion
-
 # IDE0005: Using directive is unnecessary.
 dotnet_diagnostic.IDE0005.severity = suggestion
 

src/Microsoft.DotNet.Wpf/src/Common/src/System/SR.cs

@@ -53,7 +53,7 @@ internal static string GetResourceString(string resourceKey, string defaultStrin
         {
             string resourceString = GetResourceString(resourceKey);
 
-            if (defaultString != null && resourceKey.Equals(resourceString, StringComparison.Ordinal))
+            if (defaultString is not null && resourceKey.Equals(resourceString, StringComparison.Ordinal))
             {
                 return defaultString;
             }
@@ -63,7 +63,7 @@ internal static string GetResourceString(string resourceKey, string defaultStrin
 
         internal static string Format(string resourceFormat, params object[] args)
         {
-            if (args != null)
+            if (args is not null)
             {
                 if (UsingResourceKeys())
                 {

src/Microsoft.DotNet.Wpf/src/Shared/MS/Internal/CriticalExceptions.cs

@@ -47,7 +47,7 @@ internal static Exception Unwrap(Exception ex)
         {
             // for certain types of exceptions, we care more about the inner
             // exception
-            while (ex.InnerException != null &&
+            while (ex.InnerException is not null &&
                     (   ex is System.Reflection.TargetInvocationException
                     ))
             {

src/Microsoft.DotNet.Wpf/src/Shared/MS/Internal/SafeSecurityHelper.cs

@@ -144,9 +144,9 @@ internal static Assembly GetLoadedAssembly(AssemblyName assemblyName)
                 byte[] curKeyToken = curAsmName.GetPublicKeyToken();
 
                 if (string.Equals(curAsmName.Name, assemblyName.Name, StringComparison.InvariantCultureIgnoreCase) &&
-                     (reqVersion == null || reqVersion.Equals(curVersion)) &&
-                     (reqCulture == null || reqCulture.Equals(curCulture)) &&
-                     (reqKeyToken == null || IsSameKeyToken(reqKeyToken, curKeyToken)))
+                     (reqVersion is null || reqVersion.Equals(curVersion)) &&
+                     (reqCulture is null || reqCulture.Equals(curCulture)) &&
+                     (reqKeyToken is null || IsSameKeyToken(reqKeyToken, curKeyToken)))
                 {
                     return assemblies[i];
                 }
@@ -160,7 +160,7 @@ static AssemblyName GetAssemblyName(Assembly assembly)
             lock (syncObject)
             {
                 AssemblyName result;
-                if (_assemblies == null)
+                if (_assemblies is null)
                 {
                     _assemblies = new Dictionary<object, AssemblyName>();
                 }
@@ -199,7 +199,7 @@ static void CleanupCollectedAssemblies(object state) // dummy parameter required
                 foreach (object key in _assemblies.Keys)
                 {
                     WeakReference weakRef = key as WeakReference;
-                    if (weakRef == null)
+                    if (weakRef is null)
                     {
                         continue;
                     }
@@ -211,14 +211,14 @@ static void CleanupCollectedAssemblies(object state) // dummy parameter required
                     else
                     {
                         // The target has been collected, add it to our list of keys to remove
-                        if (keysToRemove == null)
+                        if (keysToRemove is null)
                         {
                             keysToRemove = new List<object>();
                         }
                         keysToRemove.Add(key);
                     }
                 }
-                if (keysToRemove != null)
+                if (keysToRemove is not null)
                 {
                     foreach (object key in keysToRemove)
                     {
@@ -251,12 +251,12 @@ static bool IsSameKeyToken(byte[] reqKeyToken, byte[] curKeyToken)
         {
            bool isSame = false;
 
-           if (reqKeyToken == null && curKeyToken == null)
+           if (reqKeyToken is null && curKeyToken is null)
            {
                // Both Key Tokens are not set, treat them as same.
                isSame = true;
            }
-           else if (reqKeyToken != null && curKeyToken != null)
+           else if (reqKeyToken is not null && curKeyToken is not null)
            {
                // Both KeyTokens are set.
                if (reqKeyToken.Length == curKeyToken.Length)
@@ -302,7 +302,7 @@ class WeakRefKey : WeakReference
         public WeakRefKey(object target)
             :base(target)
         {
-            Debug.Assert(target != null);
+            Debug.Assert(target is not null);
             _hashCode = target.GetHashCode();
         }
 
@@ -314,12 +314,12 @@ public override int GetHashCode()
         public override bool Equals(object o)
         {
             WeakRefKey weakRef = o as WeakRefKey;
-            if (weakRef != null)
+            if (weakRef is not null)
             {
                 object target1 = Target;
                 object target2 = weakRef.Target;
 
-                if (target1 != null && target2 != null)
+                if (target1 is not null && target2 is not null)
                 {
                     return (target1 == target2);
                 }

src/Microsoft.DotNet.Wpf/src/Shared/MS/Internal/Xaml/Context/XamlContextStack.cs

@@ -24,7 +24,7 @@ public XamlContextStack(Func<T> creationDelegate)
             _creationDelegate = creationDelegate;
             Grow();
             _depth = 0;
-            Debug.Assert(CurrentFrame != null);
+            Debug.Assert(CurrentFrame is not null);
             Debug.Assert(CurrentFrame.Depth == Depth);
         }
 
@@ -40,14 +40,14 @@ public XamlContextStack(XamlContextStack<T> source, bool copy)
             {
                 T iteratorFrame = source.CurrentFrame;
                 T lastFrameInNewStack = null;
-                while (iteratorFrame != null)
+                while (iteratorFrame is not null)
                 {
                     T newFrame = (T)iteratorFrame.Clone();
-                    if (_currentFrame == null)
+                    if (_currentFrame is null)
                     {
                         _currentFrame = newFrame;
                     }
-                    if (lastFrameInNewStack != null)
+                    if (lastFrameInNewStack is not null)
                     {
                         lastFrameInNewStack.Previous = newFrame;
                     }
@@ -83,7 +83,7 @@ public T PreviousPreviousFrame
         public T GetFrame(int depth)
         {
             T iteratorFrame = _currentFrame;
-            Debug.Assert(iteratorFrame != null);
+            Debug.Assert(iteratorFrame is not null);
             while (iteratorFrame.Depth > depth)
             {
                 iteratorFrame = (T)iteratorFrame.Previous;
@@ -95,7 +95,7 @@ public T GetFrame(int depth)
         // or we'll grab one from our recycled linked list.
         public void PushScope()
         {
-            if (_recycledFrame == null)
+            if (_recycledFrame is null)
             {
                 Grow();
             }
@@ -141,17 +141,17 @@ public string Frames
             {
                 StringBuilder sb = new StringBuilder();
                 T iteratorFrame = _currentFrame;
-                sb.AppendLine(CultureInfo.InvariantCulture, $"Stack: {(_currentFrame == null ? -1 : _currentFrame.Depth + 1)} frames");
+                sb.AppendLine(CultureInfo.InvariantCulture, $"Stack: {(_currentFrame is null ? -1 : _currentFrame.Depth + 1)} frames");
                 ShowFrame(sb, _currentFrame);
                 return sb.ToString();
             }
         }
 
         private void ShowFrame(StringBuilder sb, T iteratorFrame)
         {
-            if (iteratorFrame == null)
+            if (iteratorFrame is null)
                 return;
-            if (iteratorFrame.Previous != null)
+            if (iteratorFrame.Previous is not null)
                 ShowFrame(sb, (T)iteratorFrame.Previous);
             sb.AppendLine($"  {iteratorFrame.Depth} {iteratorFrame}");
         }

src/Microsoft.DotNet.Wpf/src/Shared/MS/Internal/Xaml/Context/XamlFrame.cs

@@ -49,7 +49,7 @@ public XamlFrame Previous
             set
             {
                 _previous = value;
-                _depth = (_previous == null) ? 0 : _previous._depth + 1;
+                _depth = (_previous is null) ? 0 : _previous._depth + 1;
             }
         }
     }

src/Microsoft.DotNet.Wpf/src/Shared/MS/Internal/Xaml/Parser/SpecialBracketCharacters.cs

@@ -34,7 +34,7 @@ internal SpecialBracketCharacters()
         internal SpecialBracketCharacters(IReadOnlyDictionary<char,char> attributeList)
         {
             BeginInit();
-            if (attributeList != null && attributeList.Count > 0)
+            if (attributeList is not null && attributeList.Count > 0)
             {
                 Tokenize(attributeList);
             }