Lowercase URLs in ASP.NET Core 6+

Program.cs

// Program.cs

// ...

builder.Services.AddControllersWithViews();

// Use lowercase URLs
builder.Services.Configure<RouteOptions>(options => options.LowercaseUrls = true);


var app = builder.Build();

// ...

app.UseHttpsRedirection();
app.UseStaticFiles();

// Enforce lowercase URLs by redirecting uppercase to lowercase
var rewriterOptions = new RewriteOptions().Add(new RedirectLowerCaseUrlsRule());
app.UseRewriter(rewriterOptions);

app.UseRouting();

Rules-RedirectLowercaseUrlRule.cs

// Runes/RedirectLowercaseUrlRule.cs

using System.Net;
using Microsoft.AspNetCore.Rewrite;
using Microsoft.Net.Http.Headers;

namespace AppName.Rules;

public class RedirectLowerCaseUrlsRule : IRule
{
  public int StatusCode { get; } = (int)HttpStatusCode.MovedPermanently;

  public void ApplyRule(RewriteContext context)
  {
    HttpRequest request = context.HttpContext.Request;
    PathString path = context.HttpContext.Request.Path;
    HostString host = context.HttpContext.Request.Host;

    if (path.HasValue && path.Value.Any(char.IsUpper) || host.HasValue && host.Value.Any(char.IsUpper))
    {
      HttpResponse response = context.HttpContext.Response;
      response.StatusCode = StatusCode;
      response.Headers[HeaderNames.Location] = (request.Scheme + "://" + host.Value + request.PathBase.Value + request.Path.Value).ToLower() + request.QueryString;
      context.Result = RuleResult.EndResponse;
    }
    else
    {
      context.Result = RuleResult.ContinueRules;
    }
  }
}