diff --git a/.editorconfig b/.editorconfig
index ae973bf..5bc5261 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -107,7 +107,7 @@ csharp_style_unused_value_assignment_preference=discard_variable:suggestion
 csharp_style_unused_value_expression_statement_preference=discard_variable:silent
 
 # 'using' directive preferences
-csharp_using_directive_placement=inside_namespace:suggestion
+csharp_using_directive_placement=outside_namespace:error
 
 #### C# Formatting Rules ####
 
diff --git a/X10D/src/ByteExtensions.cs b/X10D/src/ByteExtensions.cs
index dd1f634..2baa8db 100644
--- a/X10D/src/ByteExtensions.cs
+++ b/X10D/src/ByteExtensions.cs
@@ -1,10 +1,10 @@
-namespace X10D
-{
-    using System;
-    using System.Collections.Generic;
-    using System.Linq;
-    using System.Text;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="byte" />.
     /// </summary>
diff --git a/X10D/src/CharExtensions.cs b/X10D/src/CharExtensions.cs
index cbdd49e..343981c 100644
--- a/X10D/src/CharExtensions.cs
+++ b/X10D/src/CharExtensions.cs
@@ -1,10 +1,10 @@
-namespace X10D
-{
-    using System;
-    using System.Collections.Generic;
-    using System.Linq;
-    using System.Text;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="char" />.
     /// </summary>
diff --git a/X10D/src/ComparableExtensions.cs b/X10D/src/ComparableExtensions.cs
index 798112b..3ff2ed1 100644
--- a/X10D/src/ComparableExtensions.cs
+++ b/X10D/src/ComparableExtensions.cs
@@ -1,7 +1,7 @@
-namespace X10D
-{
-    using System;
+using System;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="IComparable" />.
     /// </summary>
diff --git a/X10D/src/DateTimeExtensions.cs b/X10D/src/DateTimeExtensions.cs
index 84a559d..871a42e 100644
--- a/X10D/src/DateTimeExtensions.cs
+++ b/X10D/src/DateTimeExtensions.cs
@@ -1,7 +1,7 @@
-namespace X10D
-{
-    using System;
+using System;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="DateTime" />.
     /// </summary>
diff --git a/X10D/src/DictionaryExtensions.cs b/X10D/src/DictionaryExtensions.cs
index 8f12bee..2f7ce38 100644
--- a/X10D/src/DictionaryExtensions.cs
+++ b/X10D/src/DictionaryExtensions.cs
@@ -1,10 +1,10 @@
-namespace X10D
-{
-    using System.Collections.Generic;
-    using System.Linq;
-    using System.Text.RegularExpressions;
-    using System.Web;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.RegularExpressions;
+using System.Web;
 
+namespace X10D
+{
     /// <summary>
     ///     A set of extension methods for <see cref="Dictionary{TKey,TValue}" />.
     /// </summary>
diff --git a/X10D/src/DoubleExtensions.cs b/X10D/src/DoubleExtensions.cs
index bd6e531..cadf236 100644
--- a/X10D/src/DoubleExtensions.cs
+++ b/X10D/src/DoubleExtensions.cs
@@ -1,7 +1,7 @@
-namespace X10D
-{
-    using System;
+using System;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="double" />.
     /// </summary>
diff --git a/X10D/src/EndPointExtensions.cs b/X10D/src/EndPointExtensions.cs
index 7da5099..01fd9e4 100644
--- a/X10D/src/EndPointExtensions.cs
+++ b/X10D/src/EndPointExtensions.cs
@@ -1,7 +1,7 @@
-namespace X10D
-{
-    using System.Net;
+using System.Net;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="EndPoint" /> and derived types.
     /// </summary>
diff --git a/X10D/src/EnumerableExtensions.cs b/X10D/src/EnumerableExtensions.cs
index 9d09e43..10e937b 100644
--- a/X10D/src/EnumerableExtensions.cs
+++ b/X10D/src/EnumerableExtensions.cs
@@ -1,8 +1,8 @@
-namespace X10D
-{
-    using System.Collections.Generic;
-    using System.Linq;
+using System.Collections.Generic;
+using System.Linq;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="IEnumerable{T}" />.
     /// </summary>
diff --git a/X10D/src/Int16Extensions.cs b/X10D/src/Int16Extensions.cs
index 264891f..3782ec0 100644
--- a/X10D/src/Int16Extensions.cs
+++ b/X10D/src/Int16Extensions.cs
@@ -1,7 +1,7 @@
-namespace X10D
-{
-    using System;
+using System;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="short" />.
     /// </summary>
diff --git a/X10D/src/Int32Extensions.cs b/X10D/src/Int32Extensions.cs
index 309cfe5..2601816 100644
--- a/X10D/src/Int32Extensions.cs
+++ b/X10D/src/Int32Extensions.cs
@@ -1,7 +1,7 @@
-namespace X10D
-{
-    using System;
+using System;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="int" />.
     /// </summary>
diff --git a/X10D/src/Int64Extensions.cs b/X10D/src/Int64Extensions.cs
index 8a54030..1d5401b 100644
--- a/X10D/src/Int64Extensions.cs
+++ b/X10D/src/Int64Extensions.cs
@@ -1,7 +1,7 @@
-namespace X10D
-{
-    using System;
+using System;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="long" />.
     /// </summary>
diff --git a/X10D/src/ListExtensions.cs b/X10D/src/ListExtensions.cs
index e4e5086..1e620e8 100644
--- a/X10D/src/ListExtensions.cs
+++ b/X10D/src/ListExtensions.cs
@@ -1,9 +1,9 @@
-namespace X10D
-{
-    using System;
-    using System.Collections.Generic;
-    using System.Linq;
+using System;
+using System.Collections.Generic;
+using System.Linq;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="IList{T}" />.
     /// </summary>
diff --git a/X10D/src/RandomExtensions.cs b/X10D/src/RandomExtensions.cs
index 0008338..072ab05 100644
--- a/X10D/src/RandomExtensions.cs
+++ b/X10D/src/RandomExtensions.cs
@@ -1,9 +1,9 @@
-namespace X10D
-{
-    using System;
-    using System.Collections.Generic;
-    using System.Linq;
+using System;
+using System.Collections.Generic;
+using System.Linq;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="Random" />.
     /// </summary>
diff --git a/X10D/src/ReflectionExtensions.cs b/X10D/src/ReflectionExtensions.cs
index ff3cb23..4e87200 100644
--- a/X10D/src/ReflectionExtensions.cs
+++ b/X10D/src/ReflectionExtensions.cs
@@ -1,9 +1,9 @@
-namespace X10D
-{
-    using System;
-    using System.ComponentModel;
-    using System.Reflection;
+using System;
+using System.ComponentModel;
+using System.Reflection;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for various reflection types.
     /// </summary>
diff --git a/X10D/src/SingleExtensions.cs b/X10D/src/SingleExtensions.cs
index 53f6925..ecf07b4 100644
--- a/X10D/src/SingleExtensions.cs
+++ b/X10D/src/SingleExtensions.cs
@@ -1,7 +1,7 @@
-namespace X10D
-{
-    using System;
+using System;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="float" />.
     /// </summary>
diff --git a/X10D/src/StreamExtensions.cs b/X10D/src/StreamExtensions.cs
index 521796b..19405e5 100644
--- a/X10D/src/StreamExtensions.cs
+++ b/X10D/src/StreamExtensions.cs
@@ -1,9 +1,9 @@
-namespace X10D
-{
-    using System;
-    using System.IO;
-    using System.Security.Cryptography;
+using System;
+using System.IO;
+using System.Security.Cryptography;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="Stream" />.
     /// </summary>
diff --git a/X10D/src/StringExtensions.cs b/X10D/src/StringExtensions.cs
index 8287064..8c278d0 100644
--- a/X10D/src/StringExtensions.cs
+++ b/X10D/src/StringExtensions.cs
@@ -1,12 +1,10 @@
-namespace X10D
-{
-    using System;
-    using System.Collections.Generic;
-    using System.Linq;
-    using System.Net;
-    using System.Security;
-    using System.Text;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="string" />.
     /// </summary>
diff --git a/X10D/src/StructExtensions.cs b/X10D/src/StructExtensions.cs
index cb9aac7..92f5da5 100644
--- a/X10D/src/StructExtensions.cs
+++ b/X10D/src/StructExtensions.cs
@@ -1,7 +1,7 @@
-namespace X10D
-{
-    using System;
+using System;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see langword="struct" /> types.
     /// </summary>
diff --git a/X10D/src/TimeSpanParser.cs b/X10D/src/TimeSpanParser.cs
index 5f5a7aa..edfbb78 100644
--- a/X10D/src/TimeSpanParser.cs
+++ b/X10D/src/TimeSpanParser.cs
@@ -1,9 +1,9 @@
-namespace X10D
-{
-    using System;
-    using System.Diagnostics;
-    using System.Text.RegularExpressions;
+using System;
+using System.Diagnostics;
+using System.Text.RegularExpressions;
 
+namespace X10D
+{
     /// <summary>
     ///     Represents a class which contains a <see cref="string" /> parser which converts into <see cref="TimeSpan" />.
     /// </summary>
diff --git a/X10D/src/WaitHandleExtensions.cs b/X10D/src/WaitHandleExtensions.cs
index 9febee6..000e08a 100644
--- a/X10D/src/WaitHandleExtensions.cs
+++ b/X10D/src/WaitHandleExtensions.cs
@@ -1,8 +1,8 @@
-namespace X10D
-{
-    using System.Threading;
-    using System.Threading.Tasks;
+using System.Threading;
+using System.Threading.Tasks;
 
+namespace X10D
+{
     /// <summary>
     ///     Extension methods for <see cref="WaitHandle" />.
     /// </summary>