Move unique constraint check to extension method

src/NuGet.Services.Entities/Extensions/ExceptionExtensions.cs

@@ -0,0 +1,34 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Data;
+using System.Data.SqlClient;
+
+namespace NuGet.Services.Entities
+{
+    public static class ExceptionExtensions
+    {
+        public static bool IsSqlUniqueConstraintViolation(this DataException exception)
+        {
+            Exception current = exception;
+            while (current is not null)
+            {
+                if (current is SqlException sqlException)
+                {
+                    switch (sqlException.Number)
+                    {
+                        case 547:  // Constraint check violation: https://learn.microsoft.com/en-us/sql/relational-databases/errors-events/database-engine-events-and-errors-0-to-999
+                        case 2601: // Duplicated key row error: https://learn.microsoft.com/en-us/sql/relational-databases/replication/mssql-eng002601
+                        case 2627: // Unique constraint error: https://learn.microsoft.com/en-us/sql/relational-databases/replication/mssql-eng002627
+                            return true;
+                    }
+                }
+
+                current = current.InnerException;
+            }
+
+            return false;
+        }
+    }
+}

src/NuGetGallery/Services/PackageUploadService.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -283,21 +283,9 @@ private bool IsConflict(Exception ex)
             {
                 return true;
             }
-            else if (ex is DbUpdateException dbUpdateEx)
+            else if (ex is DbUpdateException dbUpdateEx && dbUpdateEx.IsSqlUniqueConstraintViolation())
             {
-                if (dbUpdateEx.InnerException?.InnerException != null)
-                {
-                    if (dbUpdateEx.InnerException.InnerException is SqlException sqlException)
-                    {
-                        switch (sqlException.Number)
-                        {
-                            case 547:   // Constraint check violation
-                            case 2601:  // Duplicated key row error
-                            case 2627:  // Unique constraint error
-                                return true;
-                        }
-                    }
-                }
+                return true;
             }
 
             return false;