microsoft · Evangelink · Feb 18, 2026
diff --git a/src/TestFramework/TestFramework/Assertions/Assert.AreSame.cs b/src/TestFramework/TestFramework/Assertions/Assert.AreSame.cs
@@ -80,9 +80,13 @@ internal void ComputeAssertion(string expectedExpression, string actualExpressio
     public readonly struct AssertAreNotSameInterpolatedStringHandler<TArgument>
     {
         private readonly StringBuilder? _builder;
+        private readonly TArgument? _notExpected;
+        private readonly TArgument? _actual;
 
         public AssertAreNotSameInterpolatedStringHandler(int literalLength, int formattedCount, TArgument? notExpected, TArgument? actual, out bool shouldAppend)
         {
+            _notExpected = notExpected;
+            _actual = actual;
             shouldAppend = IsAreNotSameFailing(notExpected, actual);
             if (shouldAppend)
             {
@@ -95,7 +99,7 @@ internal void ComputeAssertion(string notExpectedExpression, string actualExpres
             if (_builder is not null)
             {
                 _builder.Insert(0, string.Format(CultureInfo.CurrentCulture, FrameworkMessages.CallerArgumentExpressionTwoParametersMessage, "notExpected", notExpectedExpression, "actual", actualExpression) + " ");
-                ThrowAssertAreNotSameFailed(_builder.ToString());
+                ThrowAssertAreNotSameFailed(_notExpected, _actual, _builder.ToString());
             }
         }
 
@@ -187,14 +191,22 @@ private static bool IsAreSameFailing<T>(T? expected, T? actual)
     [DoesNotReturn]
     private static void ThrowAssertAreSameFailed<T>(T? expected, T? actual, string userMessage)
     {
-        string finalMessage = userMessage;
-        if (expected is ValueType && actual is ValueType)
-        {
-            finalMessage = string.Format(
+        string finalMessage = expected is null
+            ? string.Format(
                 CultureInfo.CurrentCulture,
-                FrameworkMessages.AreSameGivenValues,
-                userMessage);
-        }
+                FrameworkMessages.AreSameExpectedIsNull,
+                userMessage)
+            : actual is null
+                ? string.Format(
+                    CultureInfo.CurrentCulture,
+                    FrameworkMessages.AreSameActualIsNull,
+                    userMessage)
+                : expected is ValueType && actual is ValueType
+                    ? string.Format(
+                        CultureInfo.CurrentCulture,
+                        FrameworkMessages.AreSameGivenValues,
+                        userMessage)
+                    : userMessage;
 
         ThrowAssertFailed("Assert.AreSame", finalMessage);
     }
@@ -240,14 +252,23 @@ public static void AreNotSame<T>(T? notExpected, T? actual, string? message = ""
     {
         if (IsAreNotSameFailing(notExpected, actual))
         {
-            ThrowAssertAreNotSameFailed(BuildUserMessageForNotExpectedExpressionAndActualExpression(message, notExpectedExpression, actualExpression));
+            ThrowAssertAreNotSameFailed(notExpected, actual, BuildUserMessageForNotExpectedExpressionAndActualExpression(message, notExpectedExpression, actualExpression));
         }
     }
 
     private static bool IsAreNotSameFailing<T>(T? notExpected, T? actual)
         => object.ReferenceEquals(notExpected, actual);
 
     [DoesNotReturn]
-    private static void ThrowAssertAreNotSameFailed(string userMessage)
-        => ThrowAssertFailed("Assert.AreNotSame", userMessage);
+    private static void ThrowAssertAreNotSameFailed<T>(T? notExpected, T? actual, string userMessage)
+    {
+        string finalMessage = notExpected is null && actual is null
+            ? string.Format(
+                CultureInfo.CurrentCulture,
+                FrameworkMessages.AreNotSameBothNull,
+                userMessage)
+            : userMessage;
+
+        ThrowAssertFailed("Assert.AreNotSame", finalMessage);
+    }
 }
diff --git a/src/TestFramework/TestFramework/Resources/FrameworkMessages.resx b/src/TestFramework/TestFramework/Resources/FrameworkMessages.resx
@@ -162,9 +162,18 @@
   <data name="AreNotEqualDeltaFailMsg" xml:space="preserve">
     <value>Expected a difference greater than &lt;{3}&gt; between expected value &lt;{1}&gt; and actual value &lt;{2}&gt;. {0}</value>
   </data>
+  <data name="AreSameExpectedIsNull" xml:space="preserve">
+    <value>Expected is &lt;null&gt;. {0}</value>
+  </data>
+  <data name="AreSameActualIsNull" xml:space="preserve">
+    <value>Actual is &lt;null&gt;. {0}</value>
+  </data>
   <data name="AreSameGivenValues" xml:space="preserve">
     <value>Do not pass value types to AreSame(). Values converted to Object will never be the same. Consider using AreEqual(). {0}</value>
   </data>
+  <data name="AreNotSameBothNull" xml:space="preserve">
+    <value>Both values are &lt;null&gt;. {0}</value>
+  </data>
   <data name="BothCollectionsEmpty" xml:space="preserve">
     <value>Both collections are empty. {0}</value>
   </data>

diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.cs.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.cs.xlf
@@ -78,6 +78,21 @@
         <target state="translated">Očekáván rozdíl, který je větší jak &lt;{3}&gt; mezi očekávanou hodnotou &lt;{1}&gt; a aktuální hodnotou &lt;{2}&gt;. {0}</target>
         <note></note>
       </trans-unit>
+      <trans-unit id="AreNotSameBothNull">
+        <source>Both values are &lt;null&gt;. {0}</source>
+        <target state="new">Both values are &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameActualIsNull">
+        <source>Actual is &lt;null&gt;. {0}</source>
+        <target state="new">Actual is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameExpectedIsNull">
+        <source>Expected is &lt;null&gt;. {0}</source>
+        <target state="new">Expected is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
       <trans-unit id="AreSameGivenValues">
         <source>Do not pass value types to AreSame(). Values converted to Object will never be the same. Consider using AreEqual(). {0}</source>
         <target state="translated">Nevkládejte hodnotu typů do AreSame(). Hodnoty převedené do typu Object už nebudou nikdy stejné. Zvažte použití AreEqual(). {0}</target>

diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.de.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.de.xlf
@@ -78,6 +78,21 @@
         <target state="translated">Es wurde eine Differenz größer als &lt;{3}&gt; zwischen dem erwarteten Wert &lt;{1}&gt; und dem tatsächlichen Wert &lt;{2}&gt; erwartet. {0}</target>
         <note></note>
       </trans-unit>
+      <trans-unit id="AreNotSameBothNull">
+        <source>Both values are &lt;null&gt;. {0}</source>
+        <target state="new">Both values are &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameActualIsNull">
+        <source>Actual is &lt;null&gt;. {0}</source>
+        <target state="new">Actual is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameExpectedIsNull">
+        <source>Expected is &lt;null&gt;. {0}</source>
+        <target state="new">Expected is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
       <trans-unit id="AreSameGivenValues">
         <source>Do not pass value types to AreSame(). Values converted to Object will never be the same. Consider using AreEqual(). {0}</source>
         <target state="translated">Übergeben Sie keine Werttypen an AreSame(). In ein Objekt konvertierte Werte sind niemals identisch. Verwenden Sie stattdessen AreEqual(). {0}</target>

diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.es.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.es.xlf
@@ -78,6 +78,21 @@
         <target state="translated">Se esperaba una diferencia mayor que &lt;{3}&gt; entre el valor esperado &lt;{1}&gt; y el valor actual &lt;{2}&gt;. {0}</target>
         <note></note>
       </trans-unit>
+      <trans-unit id="AreNotSameBothNull">
+        <source>Both values are &lt;null&gt;. {0}</source>
+        <target state="new">Both values are &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameActualIsNull">
+        <source>Actual is &lt;null&gt;. {0}</source>
+        <target state="new">Actual is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameExpectedIsNull">
+        <source>Expected is &lt;null&gt;. {0}</source>
+        <target state="new">Expected is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
       <trans-unit id="AreSameGivenValues">
         <source>Do not pass value types to AreSame(). Values converted to Object will never be the same. Consider using AreEqual(). {0}</source>
         <target state="translated">No pase tipos de valor a AreSame(). Los valores convertidos a Object no serán nunca iguales. Considere el uso de AreEqual(). {0}</target>

diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.fr.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.fr.xlf
@@ -78,6 +78,21 @@
         <target state="translated">Différence attendue supérieure à &lt;{3}&gt; comprise entre la valeur attendue &lt;{1}&gt; et la valeur réelle &lt;{2}&gt;. {0}</target>
         <note></note>
       </trans-unit>
+      <trans-unit id="AreNotSameBothNull">
+        <source>Both values are &lt;null&gt;. {0}</source>
+        <target state="new">Both values are &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameActualIsNull">
+        <source>Actual is &lt;null&gt;. {0}</source>
+        <target state="new">Actual is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameExpectedIsNull">
+        <source>Expected is &lt;null&gt;. {0}</source>
+        <target state="new">Expected is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
       <trans-unit id="AreSameGivenValues">
         <source>Do not pass value types to AreSame(). Values converted to Object will never be the same. Consider using AreEqual(). {0}</source>
         <target state="translated">Ne passez pas de types valeur à AreSame(). Les valeurs converties en Object ne seront plus jamais les mêmes. Si possible, utilisez AreEqual(). {0}</target>

diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.it.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.it.xlf
@@ -78,6 +78,21 @@
         <target state="translated">Prevista una differenza maggiore di &lt;{3}&gt; tra il valore previsto &lt;{1}&gt; e il valore effettivo &lt;{2}&gt;. {0}</target>
         <note></note>
       </trans-unit>
+      <trans-unit id="AreNotSameBothNull">
+        <source>Both values are &lt;null&gt;. {0}</source>
+        <target state="new">Both values are &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameActualIsNull">
+        <source>Actual is &lt;null&gt;. {0}</source>
+        <target state="new">Actual is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameExpectedIsNull">
+        <source>Expected is &lt;null&gt;. {0}</source>
+        <target state="new">Expected is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
       <trans-unit id="AreSameGivenValues">
         <source>Do not pass value types to AreSame(). Values converted to Object will never be the same. Consider using AreEqual(). {0}</source>
         <target state="translated">Non passare tipi valore a AreSame(). I valori convertiti in Object non saranno mai uguali. Usare AreEqual(). {0}</target>

diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ja.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ja.xlf
@@ -78,6 +78,21 @@
         <target state="translated">指定する値 &lt;{1}&gt; と実際の値 &lt;{2}&gt; との間には、&lt;{3}&gt; を超える差が必要です。{0}</target>
         <note></note>
       </trans-unit>
+      <trans-unit id="AreNotSameBothNull">
+        <source>Both values are &lt;null&gt;. {0}</source>
+        <target state="new">Both values are &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameActualIsNull">
+        <source>Actual is &lt;null&gt;. {0}</source>
+        <target state="new">Actual is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameExpectedIsNull">
+        <source>Expected is &lt;null&gt;. {0}</source>
+        <target state="new">Expected is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
       <trans-unit id="AreSameGivenValues">
         <source>Do not pass value types to AreSame(). Values converted to Object will never be the same. Consider using AreEqual(). {0}</source>
         <target state="translated">AreSame() には値型を渡すことはできません。オブジェクトに変換された値が同じにはなりません。AreEqual() を使用することを検討してください。{0}</target>

diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ko.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ko.xlf
@@ -78,6 +78,21 @@
         <target state="translated">예상 값 &lt;{1}&gt;과(와) 실제 값 &lt;{2}&gt;의 차이가 &lt;{3}&gt;보다 커야 합니다. {0}</target>
         <note></note>
       </trans-unit>
+      <trans-unit id="AreNotSameBothNull">
+        <source>Both values are &lt;null&gt;. {0}</source>
+        <target state="new">Both values are &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameActualIsNull">
+        <source>Actual is &lt;null&gt;. {0}</source>
+        <target state="new">Actual is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameExpectedIsNull">
+        <source>Expected is &lt;null&gt;. {0}</source>
+        <target state="new">Expected is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
       <trans-unit id="AreSameGivenValues">
         <source>Do not pass value types to AreSame(). Values converted to Object will never be the same. Consider using AreEqual(). {0}</source>
         <target state="translated">AreSame()에 값 형식을 전달하면 안 됩니다. Object로 변환된 값은 동일한 값으로 간주되지 않습니다. AreEqual()을 사용해 보세요. {0}</target>

diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.pl.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.pl.xlf
@@ -78,6 +78,21 @@
         <target state="translated">Oczekiwano różnicy większej niż &lt;{3}&gt; pomiędzy oczekiwaną wartością &lt;{1}&gt; a rzeczywistą wartością &lt;{2}&gt;. {0}</target>
         <note></note>
       </trans-unit>
+      <trans-unit id="AreNotSameBothNull">
+        <source>Both values are &lt;null&gt;. {0}</source>
+        <target state="new">Both values are &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameActualIsNull">
+        <source>Actual is &lt;null&gt;. {0}</source>
+        <target state="new">Actual is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameExpectedIsNull">
+        <source>Expected is &lt;null&gt;. {0}</source>
+        <target state="new">Expected is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
       <trans-unit id="AreSameGivenValues">
         <source>Do not pass value types to AreSame(). Values converted to Object will never be the same. Consider using AreEqual(). {0}</source>
         <target state="translated">Nie przekazuj typów wartości do metody AreSame(). Wartości przekonwertowane na typ Object nigdy nie będą takie same. Rozważ użycie metody AreEqual(). {0}</target>

diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.pt-BR.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.pt-BR.xlf
@@ -78,6 +78,21 @@
         <target state="translated">Esperada uma diferença maior que &lt;{3}&gt; entre o valor esperado &lt;{1}&gt; e o valor real &lt;{2}&gt;. {0}</target>
         <note></note>
       </trans-unit>
+      <trans-unit id="AreNotSameBothNull">
+        <source>Both values are &lt;null&gt;. {0}</source>
+        <target state="new">Both values are &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameActualIsNull">
+        <source>Actual is &lt;null&gt;. {0}</source>
+        <target state="new">Actual is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameExpectedIsNull">
+        <source>Expected is &lt;null&gt;. {0}</source>
+        <target state="new">Expected is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
       <trans-unit id="AreSameGivenValues">
         <source>Do not pass value types to AreSame(). Values converted to Object will never be the same. Consider using AreEqual(). {0}</source>
         <target state="translated">Não passe tipos de valores para AreSame(). Os valores convertidos para Object nunca serão os mesmos. Considere usar AreEqual(). {0}</target>

diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ru.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ru.xlf
@@ -78,6 +78,21 @@
         <target state="translated">Между ожидаемым значением &lt;{1}&gt; и фактическим значением &lt;{2}&gt; требуется разница более чем &lt;{3}&gt;. {0}</target>
         <note></note>
       </trans-unit>
+      <trans-unit id="AreNotSameBothNull">
+        <source>Both values are &lt;null&gt;. {0}</source>
+        <target state="new">Both values are &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameActualIsNull">
+        <source>Actual is &lt;null&gt;. {0}</source>
+        <target state="new">Actual is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameExpectedIsNull">
+        <source>Expected is &lt;null&gt;. {0}</source>
+        <target state="new">Expected is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
       <trans-unit id="AreSameGivenValues">
         <source>Do not pass value types to AreSame(). Values converted to Object will never be the same. Consider using AreEqual(). {0}</source>
         <target state="translated">Не передавайте типы значений в функцию AreSame(). Значения, преобразованные в Object, никогда не будут одинаковыми. Попробуйте использовать AreEqual(). {0}</target>

diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.tr.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.tr.xlf
@@ -78,6 +78,21 @@
         <target state="translated">Beklenen değer &lt;{1}&gt; ile gerçek değer &lt;{2}&gt; arasında, şundan büyük olan fark bekleniyor: &lt;{3}&gt;. {0}</target>
         <note></note>
       </trans-unit>
+      <trans-unit id="AreNotSameBothNull">
+        <source>Both values are &lt;null&gt;. {0}</source>
+        <target state="new">Both values are &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameActualIsNull">
+        <source>Actual is &lt;null&gt;. {0}</source>
+        <target state="new">Actual is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameExpectedIsNull">
+        <source>Expected is &lt;null&gt;. {0}</source>
+        <target state="new">Expected is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
       <trans-unit id="AreSameGivenValues">
         <source>Do not pass value types to AreSame(). Values converted to Object will never be the same. Consider using AreEqual(). {0}</source>
         <target state="translated">AreSame()'e değer türleri geçirmeyin. Object olarak dönüştürülen değerler asla aynı olamayacak. AreEqual() kullanmayı düşün. {0}</target>

diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.zh-Hans.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.zh-Hans.xlf
@@ -78,6 +78,21 @@
         <target state="translated">预期值 &lt;{1}&gt; 和实际值 &lt;{2}&gt; 之间的差应大于 &lt;{3}&gt;。{0}</target>
         <note></note>
       </trans-unit>
+      <trans-unit id="AreNotSameBothNull">
+        <source>Both values are &lt;null&gt;. {0}</source>
+        <target state="new">Both values are &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameActualIsNull">
+        <source>Actual is &lt;null&gt;. {0}</source>
+        <target state="new">Actual is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
+      <trans-unit id="AreSameExpectedIsNull">
+        <source>Expected is &lt;null&gt;. {0}</source>
+        <target state="new">Expected is &lt;null&gt;. {0}</target>
+        <note></note>
+      </trans-unit>
       <trans-unit id="AreSameGivenValues">
         <source>Do not pass value types to AreSame(). Values converted to Object will never be the same. Consider using AreEqual(). {0}</source>
         <target state="translated">不要向 AreSame() 传递值类型。转换为 Object 的值将永远不会相等。请考虑使用 AreEqual()。{0}</target>