Return 400 for invalid If-Match values

src/Service.Tests/SqlTests/RestApiTests/Patch/PatchApiTestBase.cs

@@ -485,6 +485,37 @@ await SetupAndRunRestApiTest(
                 );
         }
 
+        /// <summary>
+        /// Tests that a PATCH request with an invalid If-Match header value
+        /// (anything other than "*") returns a 400 Bad Request response
+        /// because ETags are not supported.
+        /// </summary>
+        [TestMethod]
+        public virtual async Task PatchOne_Update_InvalidIfMatchHeader_Returns400_Test()
+        {
+            Dictionary<string, StringValues> headerDictionary = new();
+            headerDictionary.Add("If-Match", "\"abc123\"");
+            string requestBody = @"
+            {
+                ""title"": ""The Hobbit Returns to The Shire"",
+                ""publisher_id"": 1234
+            }";
+
+            await SetupAndRunRestApiTest(
+                    primaryKeyRoute: "id/1",
+                    queryString: null,
+                    entityNameOrPath: _integrationEntityName,
+                    sqlQuery: string.Empty,
+                    operationType: EntityActionOperation.UpsertIncremental,
+                    headers: new HeaderDictionary(headerDictionary),
+                    requestBody: requestBody,
+                    exceptionExpected: true,
+                    expectedErrorMessage: "Etags not supported, use '*'",
+                    expectedStatusCode: HttpStatusCode.BadRequest,
+                    expectedSubStatusCode: DataApiBuilderException.SubStatusCodes.BadRequest.ToString()
+                );
+        }
+
         /// <summary>
         /// Test to validate successful execution of PATCH operation which satisfies the database policy for the update operation it resolves into.
         /// </summary>

src/Service.Tests/SqlTests/RestApiTests/Put/PutApiTestBase.cs

@@ -1114,6 +1114,37 @@ await SetupAndRunRestApiTest(
                 );
         }
 
+        /// <summary>
+        /// Tests that a PUT request with an invalid If-Match header value
+        /// (anything other than "*") returns a 400 Bad Request response
+        /// because ETags are not supported.
+        /// </summary>
+        [TestMethod]
+        public virtual async Task PutOne_Update_InvalidIfMatchHeader_Returns400_Test()
+        {
+            Dictionary<string, StringValues> headerDictionary = new();
+            headerDictionary.Add("If-Match", "\"abc123\"");
+            string requestBody = @"
+            {
+                ""title"": ""The Return of the King"",
+                ""publisher_id"": 1234
+            }";
+
+            await SetupAndRunRestApiTest(
+                    primaryKeyRoute: "id/1",
+                    queryString: null,
+                    entityNameOrPath: _integrationEntityName,
+                    sqlQuery: string.Empty,
+                    operationType: EntityActionOperation.Upsert,
+                    headers: new HeaderDictionary(headerDictionary),
+                    requestBody: requestBody,
+                    exceptionExpected: true,
+                    expectedErrorMessage: "Etags not supported, use '*'",
+                    expectedStatusCode: HttpStatusCode.BadRequest,
+                    expectedSubStatusCode: DataApiBuilderException.SubStatusCodes.BadRequest.ToString()
+                );
+        }
+
         /// <summary>
         /// Tests that a PUT request with If-Match header (strict update semantics)
         /// still requires a primary key route. When If-Match is present, the operation

src/Service/Controllers/RestController.cs

@@ -161,7 +161,7 @@ public async Task<IActionResult> Upsert(
         {
             return await HandleOperation(
                 route,
-                DeterminePatchPutSemantics(EntityActionOperation.Upsert));
+                EntityActionOperation.Upsert);
         }
 
         /// <summary>
@@ -181,7 +181,7 @@ public async Task<IActionResult> UpsertIncremental(
         {
             return await HandleOperation(
                 route,
-                DeterminePatchPutSemantics(EntityActionOperation.UpsertIncremental));
+                EntityActionOperation.UpsertIncremental);
         }
 
         /// <summary>
@@ -206,6 +206,11 @@ private async Task<IActionResult> HandleOperation(
             {
                 TelemetryMetricsHelper.IncrementActiveRequests(ApiType.REST);
 
+                if (operationType is EntityActionOperation.Upsert or EntityActionOperation.UpsertIncremental)
+                {
+                    operationType = DeterminePatchPutSemantics(operationType);
+                }
+
                 if (activity is not null)
                 {
                     activity.TrackMainControllerActivityStarted(