diff --git a/X10D/src/Collections/ByteExtensions.cs b/X10D/src/Collections/ByteExtensions.cs
index 2d82e1b..ecde8af 100644
--- a/X10D/src/Collections/ByteExtensions.cs
+++ b/X10D/src/Collections/ByteExtensions.cs
@@ -22,9 +22,9 @@ public static class ByteExtensions
     [Pure]
     public static bool[] Unpack(this byte value)
     {
-        Span<bool> buffer = stackalloc bool[Size];
+        bool[] buffer = new bool[Size];
         value.Unpack(buffer);
-        return buffer.ToArray();
+        return buffer;
     }
 
     /// <summary>
diff --git a/X10D/src/Collections/CollectionExtensions.cs b/X10D/src/Collections/CollectionExtensions.cs
index 6bad398..ae33488 100644
--- a/X10D/src/Collections/CollectionExtensions.cs
+++ b/X10D/src/Collections/CollectionExtensions.cs
@@ -69,7 +69,7 @@ public static class CollectionExtensions
                 continue;
             }
 
-            await item.DisposeAsync();
+            await item.DisposeAsync().ConfigureAwait(false);
         }
 
         source.Clear();
diff --git a/X10D/src/Collections/DictionaryExtensions.cs b/X10D/src/Collections/DictionaryExtensions.cs
index 29d241e..3d25009 100644
--- a/X10D/src/Collections/DictionaryExtensions.cs
+++ b/X10D/src/Collections/DictionaryExtensions.cs
@@ -58,7 +58,8 @@ public static class DictionaryExtensions
         if (exists)
         {
             value = updateValueFactory(key, value!);
-        } else
+        }
+        else
         {
             value = addValue;
         }
@@ -67,11 +68,15 @@ public static class DictionaryExtensions
 #else
         if (dictionary.TryGetValue(key, out var old))
         {
-            dictionary[key] = updateValueFactory(key, old);
+            var newValue = updateValueFactory(key, old);
+            dictionary[key] = newValue;
+
+            return newValue;
         }
         else
         {
             dictionary.Add(key, addValue);
+            return addValue;
         }
 #endif
     }
@@ -121,14 +126,16 @@ public static class DictionaryExtensions
 
         if (dictionary.TryGetValue(key, out var old))
         {
-            dictionary[key] = updateValueFactory(key, old);
+            var newValue = updateValueFactory(key, old);
+            dictionary[key] = newValue;
+
+            return newValue;
         }
         else
         {
             dictionary.Add(key, addValue);
+            return addValue;
         }
-
-        return dictionary[key];
     }
 
     /// <summary>
@@ -199,14 +206,18 @@ public static class DictionaryExtensions
 #else
         if (dictionary.TryGetValue(key, out var old))
         {
-            dictionary[key] = updateValueFactory(key, old);
+            var update = updateValueFactory(key, old);
+            dictionary[key] = update;
+
+            return update;
         }
         else
         {
-            dictionary.Add(key, addValueFactory(key));
-        }
+            var add = addValueFactory(key);
+            dictionary.Add(key, add);
 
-        return dictionary[key];
+            return add;
+        }
 #endif
     }
 
@@ -265,14 +276,18 @@ public static class DictionaryExtensions
 
         if (dictionary.TryGetValue(key, out var old))
         {
-            dictionary[key] = updateValueFactory(key, old);
+            var update = updateValueFactory(key, old);
+            dictionary[key] = update;
+
+            return update;
         }
         else
         {
-            dictionary.Add(key, addValueFactory(key));
-        }
+            var add = addValueFactory(key);
+            dictionary.Add(key, add);
 
-        return dictionary[key];
+            return add;
+        }
     }
 
     /// <summary>
@@ -349,14 +364,18 @@ public static class DictionaryExtensions
 #else
         if (dictionary.TryGetValue(key, out var old))
         {
-            dictionary[key] = updateValueFactory(key, old, factoryArgument);
+            var update = updateValueFactory(key, old, factoryArgument);
+            dictionary[key] = update;
+
+            return update;
         }
         else
         {
-            dictionary.Add(key, addValueFactory(key, factoryArgument));
-        }
+            var add = addValueFactory(key, factoryArgument);
+            dictionary.Add(key, add);
 
-        return dictionary[key];
+            return add;
+        }
 #endif
     }
 
@@ -421,14 +440,18 @@ public static class DictionaryExtensions
 
         if (dictionary.TryGetValue(key, out var old))
         {
-            dictionary[key] = updateValueFactory(key, old, factoryArgument);
+            var update = updateValueFactory(key, old, factoryArgument);
+            dictionary[key] = update;
+
+            return update;
         }
         else
         {
-            dictionary.Add(key, addValueFactory(key, factoryArgument));
-        }
+            var add = addValueFactory(key, factoryArgument);
+            dictionary.Add(key, add);
 
-        return dictionary[key];
+            return add;
+        }
     }
 
     /// <summary>
diff --git a/X10D/src/Collections/EnumerableExtensions.cs b/X10D/src/Collections/EnumerableExtensions.cs
index 4a75370..f05b783 100644
--- a/X10D/src/Collections/EnumerableExtensions.cs
+++ b/X10D/src/Collections/EnumerableExtensions.cs
@@ -124,7 +124,7 @@ public static class EnumerableExtensions
                 continue;
             }
 
-            await item.DisposeAsync();
+            await item.DisposeAsync().ConfigureAwait(false);
         }
     }
 
diff --git a/X10D/src/Core/SpanExtensions.cs b/X10D/src/Core/SpanExtensions.cs
index 4462d2a..af5dfdd 100644
--- a/X10D/src/Core/SpanExtensions.cs
+++ b/X10D/src/Core/SpanExtensions.cs
@@ -22,7 +22,7 @@ public static class SpanExtensions
 #else
     [MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
 #endif
-    public static bool Contains<T>(this Span<T> span, T value) where T : Enum
+    public static bool Contains<T>(this Span<T> span, T value) where T : struct, Enum
     {
         return Contains((ReadOnlySpan<T>)span, value);
     }
@@ -40,12 +40,15 @@ public static class SpanExtensions
 #else
     [MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
 #endif
-    public static bool Contains<T>(this ReadOnlySpan<T> span, T value)
+    public static bool Contains<T>(this ReadOnlySpan<T> span, T value) where T : struct, Enum
     {
+#if NET6_0_OR_GREATER
         // Use MemoryMarshal.CreateSpan instead of using creating new Span instance from pointer will trim down a lot of instructions
         // on Release mode.
         // https://sharplab.io/#v2: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=
 
+        // Also use reference instead of MemoryMarshal.Cast to remove boundary check (or something, it just result in something like that).
+
         // TODO: Figure out some kind of way to directly pass the Span directly into Contains call, which make method smaller and more prone to inlining...
         unsafe
         {
@@ -85,5 +88,16 @@ public static class SpanExtensions
             }
 #pragma warning restore CS8500 // This takes the address of, gets the size of, or declares a pointer to a managed type
         }
+#else   // NET6_0_OR_GREATER
+        foreach (var it in span)
+        {
+            if (EqualityComparer<T>.Default.Equals(it, value))
+            {
+                return true;
+            }
+        }
+
+        return false;
+#endif  // NET6_0_OR_GREATER
     }
 }
diff --git a/X10D/src/IO/DoubleExtensions.cs b/X10D/src/IO/DoubleExtensions.cs
index a981d23..f71e4be 100644
--- a/X10D/src/IO/DoubleExtensions.cs
+++ b/X10D/src/IO/DoubleExtensions.cs
@@ -17,9 +17,9 @@ public static class DoubleExtensions
     [Pure]
     public static byte[] GetBytes(this double value)
     {
-        Span<byte> buffer = stackalloc byte[8];
+        byte[] buffer = new byte[8];
         value.TryWriteBytes(buffer);
-        return buffer.ToArray();
+        return buffer;
     }
 
     /// <summary>
@@ -31,9 +31,9 @@ public static class DoubleExtensions
     [Pure]
     public static byte[] GetBytes(this double value, Endianness endianness)
     {
-        Span<byte> buffer = stackalloc byte[8];
+        byte[] buffer = new byte[8];
         value.TryWriteBytes(buffer, endianness);
-        return buffer.ToArray();
+        return buffer;
     }
 
     /// <summary>
diff --git a/X10D/src/IO/Int16Extensions.cs b/X10D/src/IO/Int16Extensions.cs
index 61be94a..60b0b87 100644
--- a/X10D/src/IO/Int16Extensions.cs
+++ b/X10D/src/IO/Int16Extensions.cs
@@ -16,9 +16,9 @@ public static class Int16Extensions
     [Pure]
     public static byte[] GetBytes(this short value)
     {
-        Span<byte> buffer = stackalloc byte[2];
+        byte[] buffer = new byte[2];
         value.TryWriteBytes(buffer);
-        return buffer.ToArray();
+        return buffer;
     }
 
     /// <summary>
@@ -30,9 +30,9 @@ public static class Int16Extensions
     [Pure]
     public static byte[] GetBytes(this short value, Endianness endianness)
     {
-        Span<byte> buffer = stackalloc byte[2];
+        byte[] buffer = new byte[2];
         value.TryWriteBytes(buffer, endianness);
-        return buffer.ToArray();
+        return buffer;
     }
 
     /// <summary>
diff --git a/X10D/src/IO/Int32Extensions.cs b/X10D/src/IO/Int32Extensions.cs
index 44fa419..a349dec 100644
--- a/X10D/src/IO/Int32Extensions.cs
+++ b/X10D/src/IO/Int32Extensions.cs
@@ -30,7 +30,7 @@ public static class Int32Extensions
     [Pure]
     public static byte[] GetBytes(this int value, Endianness endianness)
     {
-        Span<byte> buffer = stackalloc byte[4];
+        byte[] buffer = new byte[4];
         value.TryWriteBytes(buffer, endianness);
         return buffer.ToArray();
     }
diff --git a/X10D/src/Math/ComparableExtensions.cs b/X10D/src/Math/ComparableExtensions.cs
index 06cd86a..ac6c335 100644
--- a/X10D/src/Math/ComparableExtensions.cs
+++ b/X10D/src/Math/ComparableExtensions.cs
@@ -133,7 +133,7 @@ public static class ComparableExtensions
         if (lower.GreaterThan(upper))
         {
             throw new ArgumentException(
-                string.Format(ExceptionMessages.LowerCannotBeGreaterThanUpper, lower, upper),
+                string.Format(null, ExceptionMessages.LowerCannotBeGreaterThanUpper, lower, upper),
                 nameof(lower));
         }