refactor: Use is not instead of !=

Author: linkdotnet

src/LinkDotNet.StringBuilder/ValueStringBuilder.AppendJoin.cs

@@ -55,7 +55,7 @@ private void AppendJoinInternalString<T>(ReadOnlySpan<char> separator, IEnumerab
         }
 
         var current = enumerator.Current;
-        if (current != null)
+        if (current is not null)
         {
             AppendInternal(current);
         }

src/LinkDotNet.StringBuilder/ValueStringBuilder.cs

@@ -288,7 +288,7 @@ public readonly int LastIndexOf(ReadOnlySpan<char> word, int startIndex)
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public void Dispose()
     {
-        if (arrayFromPool != null)
+        if (arrayFromPool is not null)
         {
             ArrayPool<char>.Shared.Return(arrayFromPool);
         }
@@ -328,7 +328,7 @@ ref Unsafe.As<char, byte>(ref sourceRef),
         var oldBufferFromPool = arrayFromPool;
         buffer = arrayFromPool = rented;
 
-        if (oldBufferFromPool != null)
+        if (oldBufferFromPool is not null)
         {
             ArrayPool<char>.Shared.Return(oldBufferFromPool);
         }