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.net 6 api Redirect page cannot be found

I'm creating and testing my first api, using visual studio .net 6 core and EF core. Right now I'm just trying to make sure I have everything functioning. I have a single controller, and I want to redirect to an html page that gives general API usage info. When I run the debugger and the browser opens to https://localhost:xxxx I append /api/values to the end and this gets handled by my controller:
public class ValuesController : ControllerBase
{
private readonly IWebHostEnvironment _env;
public ValuesController(IWebHostEnvironment env)
{
_env = env;
}
// GET: api/<ValuesController>
[HttpGet]
public ActionResult Get() //was return type IEnumerable<string>
{
//return new string[] { _env.ContentRootPath, _env.WebRootPath }; //<- WebRootPath returns as null
return Redirect("../Index.html");
}
//other stuff removed for brevity, just calling the above get function
}
In my code base directory I have the Index.html file created, and set to copy with a publish. But I can't get the redirect to this page to work.
The error I get is:
No webpage was found for the web address: https://localhost:xxxx/api/Index.html
HTTP ERROR 404
When I open Index.html from the file browser it renders properly in Chrome.
I have tried using Index.html, /Index.html, and ../Index.html in the redirect call all with the same error, though from different locations.
When I ran with the string array return I see that my ContentRootPath is the path to my project root (where Index.html exists), and that WebRootPath = null.
In launchSettings.json the applicationURL is listed a couple of times. The first is in iiSettings and given as http://localhost:xxxxx (does not seem to be used) and the second in profiles and given as https://localhost:xxxx;http://localhost:yyyy (I use the https port and getting the redirect in the controller to work, because the address bar shows localhost:xxxx/api/Index.html but the page is the error text above.
I have created a folder api in the project and put a copy of Index.html in there, still with the same error.
Here is my Program.cs app initialization:
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddDbContext<ApiDbContext>();
builder.Services.AddDatabaseDeveloperPageExceptionFilter();
builder.Services.AddControllers();
builder.Services.AddHealthChecks();
var app = builder.Build();
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseAuthentication();
app.MapControllers();
app.Run();
How do I serve up a static page from my api?

Ok, for some reason my googling got better after I posted this question. If anyone is looking here for a similar problem, I found the solution here.
Simply return a ContentResult object:
return new ContentResult
{
Content = System.IO.File.ReadAllText(#"./Index.html"),
ContentType = "text/html"
}; //new string[] { "value1", "value2" };
ControllerBase has a Content() method that will do this for you as well, but what I have above is working within my public ActionResult Get() method.

RedirectToAction("Directory");
You can try doing this, it will throw you directly to the Index page

Unable to set response header "Connection" in ASP.NET Core 6

I have an ASP.NET Core 6 Web API and the requirement to set a Connection: Close header in certain situations to put some legacy terminals (client) in a maintenance mode.
I can set the headers in general, but the Connection: Close header gets removed and is not part of the response.
Here is my controller:
[ApiController]
[Route("[controller]")]
public class HeaderTestController : ControllerBase
{
[HttpGet]
public IActionResult Get()
{
Response.Headers.Add("Foo", "Bar"); // part of the response
Response.Headers.Add("Connection", "close"); // NOT part of the response
return NoContent();
}
}
This is how my Program.cs looks like:
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllers();
var app = builder.Build();
app.UseHttpsRedirection();
app.UseAuthorization();
app.MapControllers();
app.Run();
When I invoke the API method, it returns the foo header but omits the Connection header:
Any idea which component is removing the Connection header and how I can bypass it?

Check method CreateResponseHeaders in HttpProtocol.cs. it is removing this header here. and I don't think any ways to bypass it.
and also this is only removed if client is making http/2 or http/3 request. if your legacy client is still using http/1.1 then it won't be removed.
Hope this helps.

Try this and add code to Program.cs:
builder.Services.AddCors(o => o.AddPolicy("MyPolicy", builder =>
{
builder.WithExposedHeaders(new string[] { "Connection"});
}));
and also add this line too:
app.UseCors("MyPolicy");
I have similar problem and solved

How to map fallback in ASP .NET Core Web API so that Blazor WASM app only intercepts requests that are not to the API

I have a Blazor WebAssembly solution with a client project, server project and shared project, based on the default solution template from Microsoft. I'm editing and debugging in Visual Studio 2019 preview with Google Chrome.
Out-of-the-box, the solution has a single start-up project, which is the server application. That server application has a project reference to the client application. You can set it to use HTTPS by checking "Enable SSL" in the server project properties and I have done that.
When you click on debug it works perfectly.
Now I want to change it so that the Blazor WASM app only responds to requests from https://localhost:44331 and not requests to https://localhost:44331/api. These requests should be dealt with by API Controller endpoints of the server application instead. So, if somebody visits https://localhost:44331/api/something, and no such API endpoint exists, they should receive a 404 error code from the API and not be routed to the usual Blazor page saying "Sorry, there's nothing at this address."
I want to use this extra "/api" portion of the URL to keep the requests to the API separate from requests for pages. I think this will be closer to how a normal setup would be in production. I hope it's clear what I'm trying to do.
Here is a sample Controller declaration with route attribute:
namespace BlazorApp2.Server.Controllers
{
[ApiController]
[Route("api/[controller]")]
public class WeatherForecastController : ControllerBase
{
// Etc.
[HttpGet]
public IEnumerable<WeatherForecast> Get()
{
//etc.
}
///etc.
}
}
Here is what I have tried in my Startup.cs and it does not work. Can anybody suggest something that will please?
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
// Etc.
app.UseStatusCodePages();
app.UseEndpoints(endpoints =>
{
endpoints.MapRazorPages();
endpoints.MapControllers();
// The line commented out below is the out-of-the-box behaviour for a Blazor WASM app with ASP NET Core API. This is the line I want to replace.
// endpoints.MapFallbackToFile("index.html");
// The line below is my (failed) attempt to get the behaviour I want.
endpoints.MapFallback(HandleFallback);
});
}
private async Task HandleFallback(HttpContext context)
{
var apiPathSegment = new PathString("/api"); // Find out from the request URL if this is a request to the API or just a web page on the Blazor WASM app.
bool isApiRequest = context.Request.Path.StartsWithSegments(apiPathSegment);
if (!isApiRequest)
{
context.Response.Redirect("index.html"); // This is a request for a web page so just do the normal out-of-the-box behaviour.
}
else
{
context.Response.StatusCode = StatusCodes.Status404NotFound; // This request had nothing to do with the Blazor app. This is just an API call that went wrong.
}
}
Does anybody know how to get this working how I'd like, please?

To recap the problem, when somebody makes a request to:
https://yourapp.com/api/someendpoint
and /api/someendpoint can't be found, they're taken to a Blazor page. This default behaviour is weird. For requests starting with /api, they were expecting an HTTP Status Code and probably a JSON object too, but instead, they got HTML. Maybe they don't even use your app. Maybe they're not even human (more likely they're a piece of software).
This is how you send them an HTTP Status Code instead.
On your controllers:
[Route("api/[controller]")]
public class SampleController : ControllerBase
{
// ...
}
In Startup.cs:
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
// ...
app.UseStaticFiles();
app.UseRouting();
app.UseEndpoints(endpoints =>
{
endpoints.MapRazorPages();
endpoints.MapControllers();
endpoints.Map("api/{**slug}", HandleApiFallback);
endpoints.MapFallbackToFile("{**slug}", "index.html");
});
}
private Task HandleApiFallback(HttpContext context)
{
context.Response.StatusCode = StatusCodes.Status404NotFound;
return Task.CompletedTask;
}

Pretty sure this should work:
endpoints.MapFallbackToFile("{*path:regex(^(?!api).*$)}", "index.html"); // don't match paths beginning with api
I think it means something like only match URLs where the path does not start with api.

You can fix this by explicitly mapping Blazor fallback only for paths that don't start with /api and, then only mapping api paths for those that do start with /api, like I mention in this answer to my owner question. This gives the benefit that instead of just returning a 404 if you try to POST to a GET api method, you will get the proper api response of 405, or whatever other error the api would normally return given the request.
//explicitly only use blazor when the path doesn't start with api
app.MapWhen(ctx => !ctx.Request.Path.StartsWithSegments("/api"), blazor =>
{
blazor.UseBlazorFrameworkFiles();
blazor.UseStaticFiles();
blazor.UseRouting();
blazor.UseEndpoints(endpoints =>
{
endpoints.MapFallbackToFile("index.html");
});
});
//explicitly map api endpoints only when path starts with api
app.MapWhen(ctx => ctx.Request.Path.StartsWithSegments("/api"), api =>
{
//if you are not using a blazor app, you can move these files out of this closure
api.UseStaticFiles();
api.UseRouting();
api.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
});
});

Using code from #Darragh I get the following error:
endpoints.MapFallbackToPage("{path:regex(^(?!api).$)}", "index.html");
System.ArgumentException: ''index.html' is not a valid page name. A
page name is path relative to the Razor Pages root directory that
starts with a leading forward slash ('/') and does not contain the
file extension e.g "/Users/Edit". (Parameter 'pageName')'
The code will run if I use MapFallbackToFile instead of MapFallbackToPage like the original code.
However when I tested the regex it matched everything including an API URL:
https://regex101.com/r/nq7FCi/1
My Regex would look like this instead: ^(?!.*?(?:\/api\/)).*$ based on this answer:
https://stackoverflow.com/a/23207219/3850405
https://regex101.com/r/qmftyc/1
When testing this out It did not work anyway and urls containing /api/ was redirected to index.html.
My final code is based on #benjamin answer but with the original MapFallbackToFile used last.
app.UseEndpoints(endpoints =>
{
endpoints.MapRazorPages();
endpoints.MapControllers();
endpoints.Map("api/{**slug}", HandleApiFallback);
endpoints.MapFallbackToFile("index.html");
});
private Task HandleApiFallback(HttpContext context)
{
context.Response.StatusCode = StatusCodes.Status404NotFound;
return Task.CompletedTask;
}

I have tried this with Blazor WebAssembly .NET 5. After publishing to IIS, the previously suggested solutions do not work.
The answer to this question is provided here. Tested and working.
Shortly:
Edit wwwroot\service-worker.published.js file and add the path to exclude, in this case /api/.
const shouldServeIndexHtml = event.request.mode === 'navigate' &&
!event.request.url.includes('/api/')

If you start from a Blazor WASM hosted solution, you'll a get a sample, just launch
dotnet new blazorwasm --hosted
It create a solution with 3 projects :
|-- Client
|-- Server
|-- Shared
In The Server Startup class, the middleware pipeline is setup like this :
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
app.UseWebAssemblyDebugging();
}
else
{
app.UseExceptionHandler("/Error");
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseBlazorFrameworkFiles();
app.UseStaticFiles();
app.UseRouting();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
endpoints.MapFallbackToFile("index.html");
});
}
The controller define its route with Route attribute. If you want to host the controller at /api/{controller} use the Route attribute value api/[controller]:
[ApiController]
[Route("api/[controller]")]
public class WeatherForecastController : ControllerBase

With all other solutions applied, I still encounter the problem in ASP.NET Core 7 (not sure if the version matters) and it only happens on Production server. Turned out there's this difference between dev and production environment:
if (app.Environment.IsDevelopment())
{
app.UseWebAssemblyDebugging();
}
else
{
app.UseExceptionHandler("/Error"); // <-- This line
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
Removing app.UseExceptionHandler and I can see exceptions again.

ASP.NET Core - Swashbuckle not creating swagger.json file

I am having trouble getting the Swashbuckle.AspNetCore (1.0.0) package to generate any output. I read the swagger.json file should be written to '~/swagger/docs/v1'. However, I am not getting any output.
I started with a brand new ASP.NET Core API project. I should mention this is ASP.NET Core 2. The API works, and I am able to retrieve values from the values controller just fine.
My startup class has the configuration exactly as described in this article (Swashbuckle.AspNetCore on GitHub).
public class Startup
{
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
public IConfiguration Configuration { get; }
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc();
services.AddSwaggerGen(c =>
{
c.SwaggerDoc("v1", new Info { Title = "My API", Version = "v1" });
});
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
// Enable middleware to serve generated Swagger as a JSON endpoint.
app.UseSwagger();
app.UseSwaggerUI(c =>
{
c.SwaggerEndpoint("/swagger/v1/swagger.json", "MyAPI V1");
});
}
else
{
app.UseExceptionHandler();
}
app.UseStatusCodePages();
app.UseMvc();
//throw new Exception();
}
}
You can see the NuGet references...
Again, this is all the default template, but I include the ValuesController for reference...
[Route("api/[controller]")]
public class ValuesController : Controller
{
// GET api/values
[HttpGet]
public IEnumerable<string> Get()
{
return new string[] { "value1", "value2" };
}
// GET api/values/5
[HttpGet("{id}")]
public string Get(int id)
{
return "value";
}
// POST api/values
[HttpPost]
public void Post([FromBody]string value)
{
}
// PUT api/values/5
[HttpPut("{id}")]
public void Put(int id, [FromBody]string value)
{
}
// DELETE api/values/5
[HttpDelete("{id}")]
public void Delete(int id)
{
}
}

I had the same problem. Check http://localhost:XXXX/swagger/v1/swagger.json. If you get any a errors, fix them.
For example, I had an ambiguous route in a base controller class and I got the error: "Ambiguous HTTP method for action. Actions require an explicit HttpMethod binding for Swagger 2.0.".
If you use base controllers make sure your public methods use the HttpGet/HttpPost/HttpPut/HttpDelete OR Route attributes to avoid ambiguous routes.
Then, also, I had defined both HttpGet("route") AND Route("route") attributes in the same method, which was the last issue for swagger.

I believe you missed these two lines on your Configure:
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
// Enable middleware to serve generated Swagger as a JSON endpoint.
app.UseSwagger();
app.UseSwaggerUI(c =>
{
c.SwaggerEndpoint("v1/swagger.json", "MyAPI V1");
});
}
To access Swagger UI, the URL should be: http://localhost:XXXX/swagger/
The json can be found at the top of Swagger UI:

If your application is hosted on IIS/IIS Express try the following:
c.SwaggerEndpoint("../swagger/v1/swagger.json", "MyAPI V1");

I was running into a similar, but not exactly the same issue with swagger. Hopefully this helps someone else.
I was using a custom document title and was not changing the folder path in the SwaggerEndPoint to match the document title. If you leave the endpoint pointing to swagger/v1/swagger.json it won't find the json file in the swagger UI.
Example:
services.AddSwaggerGen(swagger =>
{
swagger.SwaggerDoc("AppAdministration", new Info { Title = "App Administration API", Version = "v1.0" });
});
app.UseSwaggerUI(c =>
{
c.SwaggerEndpoint("/swagger/AppAdministration/swagger.json", "App Administration");
});

#if DEBUG
// For Debug in Kestrel
c.SwaggerEndpoint("/swagger/v1/swagger.json", "Web API V1");
#else
// To deploy on IIS
c.SwaggerEndpoint("/webapi/swagger/v1/swagger.json", "Web API V1");
#endif
When deployed to IIS webapi(base URL) is the Application Alias. You need to keep Application Alias(base URL) same for all IIS deployments because swagger looks for swagger.json at "/swagger/v1/swagger.json" location but wont prefix application Alias(base URL) that is the reason it wont work.
For Example:
localhost/swagger/v1/swagger.json - Couldn't find swagger.json

You must conform to 2 rules:
Decorate all actions with explicit Http Verbs like[HttpGet("xxx")], [HttpPost("xxx")], ... instead of [Route("xxx")].
Decorate public methods in controllers with [NonAction] Attribute.
Note that http://localhost:XXXX/swagger/ page requests for http://localhost:XXXX/swagger/v1/swagger.json file, but an Exception will occur from Swagger if you wouldn't conform above rules.

After watching the answers and checking the recommendations, I end up having no clue what was going wrong.
I literally tried everything. So if you end up in the same situation, understand that the issue might be something else, completely irrelevant from swagger.
In my case was a OData exception.
Here's the procedure:
1) Navigate to the localhost:xxxx/swagger
2) Open Developer tools
3) Click on the error shown in the console and you will see the inner exception that is causing the issue.

I am moving my comment to an answer since it appears to be helpful.
To avoid issues with IIS aliases, remove /swagger/ from the URL path. It should look like this:
app.UseSwaggerUI(c => { c.SwaggerEndpoint("v1/swagger.json", "API name"); });

I don't know if this is useful for someone, but in my case the problem was that the name had different casing.
V1 in the service configuration - V capital letter
v1 in Settings -- v lower case
The only thing I did was to use the same casing and it worked.

If you have any issues in your controller to map to an unique URL you get this error.
The best way to find the cause of issue is exclude all controllers from project. Then try running the app by enabling one controller or one or more methods in a controller at a time to find the controllers/ controller method(S) which have an issue. Or you could get smart and do a binary search logic to find the disable enable multiple controller/methods to find the faulty ones.
Some of the causes is
Having public methods in controller without HTTP method attributes
Having multiple methods with same Http attributes which could map to same api call if you are not using "[action]" based mapping
If you are using versioning make sure you have the method in all the controller versions (if using inheritance even though you use from base)

A common error that we make when use Swagger is to give the same name to(NET ASP) two or more routes. this cause that swagger cannot generate the JSON file. for example, this is a wrong way
[HttpPost, Route("Start")]
public async Task<TransactionResult> WipStart(BodyWipStartDTO data)
{
return await _wipServices.WipStart(data);
}
Other action with the same route name but different action name
[HttpPost, Route("Start")]
public async Task<TransactionResult> WipAbort(BodyWipStartDTO data)
{
return await _wipServices.WipAbort(data);
}
This a correct way
[HttpPost, Route("Start")]
public async Task<TransactionResult> WipStart(BodyWipStartDTO data)
{
return await _wipServices.WipStart(data);
}
[HttpPost, Route("Abort")]
public async Task<TransactionResult> WipAbort(BodyWipStartDTO data)
{
return await _wipServices.WipAbort(data);
}

You actually just need to fix the swagger url by removing the starting backslash just like this :
c.SwaggerEndpoint("swagger/v1/swagger.json", "MyAPI V1");
instead of :
c.SwaggerEndpoint("/swagger/v1/swagger.json", "MyAPI V1");

Be aware that in Visual Studio 2022 and .NetCore 6 if you create a new ASP.NET Core Web App, Program.cs has the oposite check for Development environment.
instead of
if (app.Environment.IsDevelopment())
{
app.UseSwagger();
app.UseSwaggerUI();
}
you will find
if (!app.Environment.IsDevelopment())
{
app.UseExceptionHandler("/Home/Error");
}
// You shoukd add swagger calls here
app.UseSwagger();
app.UseSwaggerUI();
If you create a new project by selecting the template ASP.NET Core Web API and check "Enable OpenAPI support" you will have different Program.cs with preinstalled swagger package and related code.
This took some time for me to find, hope to help someone.

Adding a relative path worked for me:
app.UseSwaggerUI(c =>
{
c.SwaggerEndpoint("../swagger/v1/swagger.json", "My App");
});

Personally I had the same issue and when I tried again today after a while I found in the new version (2.5.0) that going in the json I could see an explanation of the error that was in here.
Also another thing that helped to fix it to me was removing the hosting information connected to the website that is hold inside "..vs\config\applicationhost.config" at the root of the solution folder
I removed the element that was configuring the website.
<site name="**" id="9">
<application path="/" applicationPool=""></application>
<bindings></bindings>
</site>

I had this problem when I used a inner class in Post parameters
[HttpPost]
public async Task Post([FromBody] Foo value)
{
}
Where Foo is
public class Foo
{
public IEnumerable<Bar> Bars {get;set;}
public class Bar
{
}
}

Try to follow these steps, easy and clean.
Check your console are you getting any error like "Ambiguous HTTP method for action. Actions require an explicit HttpMethod binding for Swagger 2.0."
If YES:
Reason for this error: Swagger expects
each endpoint should have the method (get/post/put/delete)
.
Solution:
Revisit your each and every controller and make sure you have added
expected method.
(or you can just see in console error which controller causing ambiguity)
If NO. Please let us know your issue and solution if you have found any.

Same problem - easy fix for me.
To find the underlying problem I navigated to the actual swagger.json file which gave me the real error
/swagger/v1/swagger.json
The actual error displayed from this Url was
NotSupportedException: Ambiguous HTTP method for action ... Actions require an explicit HttpMethod binding for Swagger/OpenAPI 3.0
The point being
Actions require an explicit HttpMethod
I then decorated my controller methods with [HttpGet]
[Route("GetFlatRows")]
[HttpGet]
public IActionResult GetFlatRows()
{
Problem solved

Make sure you have all the required dependencies, go to the url xxx/swagger/v1/swagger.json you might find that you're missing one or more dependencies.

I was getting this Swagger error when I created Version 2 of my api using version headers instead of url versioning. The workaround was to add [Obsolete] attributes to the Version 1 methods then use SwaggerGeneratorOptions to ignore the obsolete api methods in Startup -> ConfigureServices method.
services.AddSwaggerGen(c =>
{
c.SwaggerGeneratorOptions.IgnoreObsoleteActions = true;
c.SwaggerDoc("v2", new Info { Title = "My API", Version = "v2" });
});

I had the same problem. I was using swagger like below mentioned pattern i.e. "../swagger/v1/swagger.json" because I am using IIS Express.Later than I change it to
"/swagger/v1/swagger.json"and clean,rebuild the solution worked for me.

You might forgetting to include.. StartUp.cs/Configure()
app.UseSwagger();
Check if you forgot to include, you error must be remove.

I'd a similar issue, my Swagger documentation broke after I was adding async version of APIs to existing ones.
I played around the Swagger DLL's by installing / Reinstalling, finally commenting newly added APIs, and it worked.
Then I added different signature in attributes, and bingo!, It worked.
In your case, you are having two API with matching signatures
[HttpGet]
public IEnumerable<string> Get()
{
return new string[] { "value1", "value2" };
}
// GET api/values/5
[HttpGet("{id}")]
public string Get(int id)
{`enter code here`
return "value";
}
Try providing different names in attributes like
[HttpGet("List")]
public IEnumerable<string> Get()
{
return new string[] { "value1", "value2" };
}
// GET api/values/5
[HttpGet("ListById/{id}")]
public string Get(int id)
{
return "value";
}
This should solve the issue.

I have came across the same issue, and noticed that my API has not hosted in the root folder and in an virtual directory.
I moved my API to the root folder in IIS and worked.
More info in this answer

Take a look on Chrome developer tools, sometimes, swagger.json request throws http 500, witch means that there is some inconsistency on your controllers.
For example: In my case, there is an "Ambiguous HTTP method for action":

Also I had an issue because I was versioning the application in IIS level like below:
If doing this then the configuration at the Configure method should append the version number like below:
app.UseSwaggerUI(options =>
{
options.SwaggerEndpoint("/1.0/swagger/V1/swagger.json", "Static Data Service");
});

I was able to fix and understand my issue when I tried to go to the swagger.json URL location:
https://localhost:XXXXX/swagger/v1/swagger.json
The page will show the error and reason why it is not found.
In my case, I saw that there was a misconfigured XML definition of one of my methods based on the error it returned:
NotSupportedException: HTTP method "GET" & path "api/Values/{id}" overloaded by actions - ...
...
...

In my case problem was in method type, should be HttpPOST but there was HttpGET
Once I changed that, everything starts work.
https://c2n.me/44p7lRd.png

You should install the following packages into your project.
5.0.0-rc4 version of Swashbuckle is the minimum. Otherwise, it won't work.
As of now, directly installing it from Nuget, installs the old versions which won't work for Core 3.
I inserted the following lines into .csproj project file like that:
<PackageReference Include="Microsoft.OpenApi" Version="1.1.4" />
<PackageReference Include="Swashbuckle.AspNetCore.Swagger" Version="5.0.0-rc4" />
<PackageReference Include="Swashbuckle.AspNetCore.SwaggerGen" Version="5.0.0-rc4" />
<PackageReference Include="Swashbuckle.AspNetCore.SwaggerUi" Version="5.0.0-rc4" />
After that, Rebuild installs the newer versions.
If not, you can use restore too.
In the Startup.cs, you should configure Swashbuckle like that:
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddControllers();
// Register the Swagger generator, defining 1 or more Swagger documents
services.AddSwaggerGen(c =>
{
c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1" });
});
services.AddMvc();
}
 
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
app.UseHttpsRedirection();
// Enable middleware to serve generated Swagger as a JSON endpoint.
app.UseSwagger();
// Enable middleware to serve swagger-ui (HTML, JS, CSS, etc.),
// specifying the Swagger JSON endpoint.
app.UseSwaggerUI(c =>
{
c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
//c.RoutePrefix = String.Empty;
});
app.UseRouting();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
});
}
Just go to the "https://localhost:5001/swagger/index.html" and you'll see the Swagger UI.
(5001 is my local port, you should change it with yours)
It took a little time for me to figure it out.
I hope it will help others :)

Answer:
If using directories or application with IIS or a reverse proxy,<br/> set the Swagger endpoint to a relative path using the ./ prefix. For example,<br/> ./swagger/v1/swagger.json. Using /swagger/v1/swagger.json instructs the app to<br/>look for the JSON file at the true root of the URL (plus the route prefix, if used). For example, use http://localhost:<br/><br/><port>/<route_prefix>/swagger/v1/swagger.json instead of http://localhost:<br/><port>/<virtual_directory>/<route_prefix>/swagger/v1/swagger.json.<br/>
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
// Enable middleware to serve generated Swagger as a JSON endpoint.
app.UseSwagger();
app.UseSwaggerUI(c =>
{
//c.SwaggerEndpoint("/swagger/v1/swagger.json", "MyAPI V1");
//Add dot in front of swagger path so that it takes relative path in server
c.SwaggerEndpoint("./swagger/v1/swagger.json", "MyAPI V1");
});
}
[Detail description of the swagger integration to web api core 3.0][1]
[1]: https://learn.microsoft.com/en-us/aspnet/core/tutorials/getting-started-with-swashbuckle?view=aspnetcore-3.1&tabs=visual-studio

How to enable https in mvc6

How I tried to do this:
1- Set filter in startup:
public IServiceProvider ConfigureServices(IServiceCollection services)
{
//...
services.AddMvc();
services.Configure<MvcOptions>(options =>
{
options.Filters.Add(new RequireHttpsAttribute());
});
2- set [RequireHttps] in cotroler
[RequireHttps]
public class HomeController : BaseController
{
public ViewResult Index()
{
return View();
}
}
3- add in project.json
"kestrel": "Microsoft.AspNet.Hosting --server=Microsoft.AspNet.Server.Kestrel --server.urls=https://localhost:1234"
And still not working.
What have I done wrong?

EDIT : This is a new feature that is not in beta8 yet. I've noticed after I've tried to find this feature in the beta8 tag on Github. It seems like your only solution for now is to either but it behind IIS (who supports HTTPS) or behind NGINX while will add that module for you.
Make sure to enable SSL in your Startup.cs/Configure method.
It is done like so:
var certPath = "c:\\mycert.pfx";
app.UseKestrelHttps(new X509Certificate2(certPath, "certificatePassword"));
The action filters will just act on the actual URL. You do need to listen on a port with a certificate on it to have to HTTPs.
Hope this helps.
Source to sample Startup.cs