RedirectMiddlewareApp

A .NET 8 Razor Pages / MVC hybrid sample demonstrating a lightweight URL redirection system backed by an in-memory cache and a pluggable redirect source. It shows how to centralize legacy URL handling without scattering rewrite logic across the app.

Key Features

• Central RedirectUrlService for resolving old -> new URLs.
• Pluggable IRedirectUrlProvider so redirects can come from config, database, JSON, etc.
• In-memory caching via IMemoryCache with configurable refresh + expiration.
• Periodic background refresh using System.Threading.Timer.
• Supports absolute or relative target URLs (URLTypeEnum).
• Clean separation in MiddlewareLibrary for reuse across applications.

How It Works

1. A request arrives.
2. Your middleware or controller (you add this) calls IRedirectUrlService.GetRedirect(path).
3. If a match exists, you issue a 301/302 to Redirect.NewUrl.
4. The service maintains a cached list of Redirect entries, auto-refreshed on an interval.

Redirect Model

Caching Behavior

• Refresh interval: RedirectCacheRefreshMinutes (background timer repopulates cache).
• Expiration: RedirectCacheExpireMinutes (absolute expiration for the cache entry).
• If the cache is empty on first use, it is populated synchronously.

Configure both to balance memory freshness vs. performance.

Configuration

In appsettings.json (example):

Service Registration (Program.cs)

Implementing a Redirect Provider

Provide your source of truth by implementing IRedirectUrlProvider:

Using the Service (Example Middleware Sketch)

public class RedirectMiddleware
{
    private readonly RequestDelegate _next;
    private readonly IRedirectUrlService _redirectUrlService;

    public RedirectMiddleware(RequestDelegate next, IRedirectUrlService redirectUrlService)
    {
        _next = next;
        _redirectUrlService = redirectUrlService;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        var path = context.Request.Path.Value;
        var redirect = _redirectUrlService.GetRedirect(path);

        if (redirect != null)
        {
            context.Response.Redirect(redirect.NewUrl, redirect.Permanently);
            return;
        }

        await _next(context);
    }
}

Navigate to: https://localhost:5001 (or shown port).

Logging

RedirectUrlService logs:

• Cache refresh operations.
• Cache hits.
• Failed provider calls (if exceptions logged externally).

Third-Party Client Libraries

Bootstrap, jQuery, and validation scripts are included under their respective MIT licenses (see /wwwroot/lib/*/LICENSE).

License

This sample code is MIT licensed (adjust if you add a license file). Third-party libraries retain their original licenses.

Next Steps

• Add real redirect provider.
• Add unit tests around RedirectUrlService.
• Add admin UI for managing redirects (optional).

Happy building!