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Migrate ASP.NET MVC 5 / .NET 4.5.1 app to ASP.NET Core on .NET 9#22

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Migrate ASP.NET MVC 5 / .NET 4.5.1 app to ASP.NET Core on .NET 9#22
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devin/1780674307-aspnetcore-net9-migration

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@devin-ai-integration devin-ai-integration Bot commented Jun 5, 2026 •
edited by staging-devin-ai-integration Bot
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Summary

Full-framework migration of the SampleMvcWebApp blogging demo from ASP.NET MVC 5 / .NET Framework 4.5.1 to ASP.NET Core on net9.0. All 5 projects are now SDK-style, EF6 is replaced by EF Core 9, and the legacy GenericServices 1.0.9 package is replaced by an in-repo compat library so controllers/views/DTOs keep their original shape.

Why a compat library instead of EfCore.GenericServices

The app is tightly coupled to the old GenericServices surface: EfGenericDto override hooks (SetupSecondaryData/CreateDataFromDto/UpdateDataFromDto), action-parameter service injection, and the ISuccessOrErrors result type used throughout controllers. EfCore.GenericServices exposes a fundamentally different ICrudServices API and cannot reproduce these patterns. Per the task note ("you may need to implement some service methods manually"), a faithful EF Core + AutoMapper reimplementation of the original interfaces was the lowest-risk path. New project: GenericServices/.

Key changes by layer

  • Projects/config: all .csproj → SDK-style net9.0; removed every packages.config, Web.config, App.config, Global.asax, App_Start/, Autofac modules, AssemblyInfo.cs. Added appsettings.json + launchSettings.json.
  • DataLayer (EF Core): SampleWebAppDb : DbContext, IGenericServicesDbContext with constructor DbContextOptions, Fluent API in OnModelCreating (Post→Blog FK, Post↔Tag many-to-many), SaveChanges hook for LastUpdated, and ExtraValidation enforcing Tag.Slug uniqueness (was EF6 ValidateEntity). DataLayerInitialise now uses EnsureCreated() + XML seed.
  • GenericServices compat lib: EfGenericDto<TData,TDto> (+ async), ISuccessOrErrors/<T>, SaveChangesWithChecking (DataAnnotations + IValidatableObject + ExtraValidation), 13 service interfaces/impls projecting via AutoMapper ProjectTo.
  • Web: Program.cs minimal hosting; built-in DI via AddServiceLayer(); DB provider selectable through config (Sqlite default for local dev, SqlServer available). Controllers inherit Core MVC and use [FromServices] for action-parameter service injection; MvcHtmlString→raw string + @Html.Raw.
  • Views: added _ViewImports.cshtml (tag helpers + usings), _Layout uses direct <link>/<script> instead of bundles, removed Views/Web.config, static assets moved to wwwroot/.
  • Tests: converted to net9.0 xUnit on EF Core InMemory; old Autofac/SignalR/System.Web tests (which tested removed infrastructure) replaced with focused data-layer + service-layer CRUD tests. 12 passing.

Verification

  • dotnet build clean across the solution; dotnet test → 12/12 pass.
  • App runs (dotnet run), seeds SQLite, and all pages return 200 (Home, Posts/Tags/Blogs + Async variants, Create/Edit/Details, secondary-data dropdowns populate).

Notes

  • Bootstrap 3 / jQuery 1.10 assets retained to keep the existing Razor markup working (a Bootstrap 5 upgrade would require rewriting all view markup); deferred as out-of-scope.
  • DelegateDecompiler/Mono.Reflection dropped — the compat library computes aggregate fields (e.g. PostsCount) via AutoMapper projection conventions instead.

Link to Devin session: https://app.devin.ai/sessions/97ae13da2ed64c0c821a10a57d4cf380
Requested by: @dillonvargo

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@devin-ai-integration @dillonvargo
feature: migrate ASP.NET MVC 5 / .NET 4.5.1 app to ASP.NET Core on .N…
dbb5c03 
…ET 9

- Convert all projects to SDK-style net9.0; remove packages.config/Web.config/App.config
- Replace EF6 with EF Core 9 (DbContext, Fluent API, EnsureCreated + seed)
- Add GenericServices compat library (EF Core + AutoMapper) preserving the
  original EfGenericDto/ISuccessOrErrors service surface
- Replace Global.asax/OWIN/Autofac/SignalR with Program.cs minimal hosting + built-in DI
- Migrate controllers to ASP.NET Core MVC ([FromServices] action injection)
- Migrate Razor views (_ViewImports, tag helpers, direct link/script tags, wwwroot)
- Convert Tests to net9.0 xUnit using EF Core in-memory (12 passing)
- Use SQLite for local dev (SqlServer provider selectable via config)

Co-Authored-By: Dillon Vargo <dillonvargo@gmail.com>
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devin-ai-integration Bot commented Jun 5, 2026

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devin-ai-integration Bot and others added 2 commits June 5, 2026 16:03
@devin-ai-integration @dillonvargo
bug: null-guard TagNames computed getter to fix Post create/edit crash
1b07236 
ASP.NET Core's validation visitor invokes all model getters during model
binding. On the posted-back Post DTO the Tags collection is null, so the
TagNames computed getter (Tags.Select(...)) threw ArgumentNullException on
Post Create/Edit. Guard the getter to return empty when Tags is null.

Co-Authored-By: Dillon Vargo <dillonvargo@gmail.com>
@devin-ai-integration @dillonvargo
test: add regression test for null-safe TagNames getter (bug fix)
7852693 
Co-Authored-By: Dillon Vargo <dillonvargo@gmail.com>
@devin-ai-integration
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devin-ai-integration Bot commented Jun 5, 2026 •
edited
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Runtime test results — migrated app on .NET 9

Ran the migrated app locally (dotnet run, SQLite seeded on startup) at http://localhost:5000 and exercised the golden-path CRUD flows through the browser UI. All assertions passed. One real bug was found and fixed during testing (now covered by a regression test).

Post Create with secondary data (the previously-broken area) — PASS

The Create form populates the Bloggers dropdown (4) + Tags multiselect (8); submitting creates the post with the correct blogger and tag names.

Post create form
Post created in list

Tag CRUD (create / validate / edit / delete) — PASS

Tags list
Tag created

Post details persisted + regression (Blogs list, PostsAsync) — PASS

Post details
Posts async

Assertions

  • It should perform full Tag CRUD (create, validate, edit, delete) — passed
  • It should create a Post with blogger dropdown + tag multiselect — passed
  • It should show Post details persisted correctly — passed
  • It should edit a Post, preserving blogger + tags — passed
  • It should delete a Post — passed
  • It should render Blogs list + async PostsAsync controller (regression) — passed

Bug found & fixed during testing

Post Create/Edit initially crashed with NullReferenceException: ASP.NET Core's validation visitor invokes the TagNames computed getter on the posted-back DTO where Tags is null. Fixed by null-guarding the getter on all 4 Post DTOs + added a regression test. All 13 xUnit tests pass.

No CI is configured on this repo, so there were no checks to wait on.

Devin session: https://app.devin.ai/sessions/97ae13da2ed64c0c821a10a57d4cf380

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