120

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...

enter image description here

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)
    {
    }
}
4
  • 2
    check output in visual studio Commented Oct 16, 2020 at 14:00
  • Its not always obvious, but when you publish make sure it publishes in 'development' environment, unless you really do want swagger in release or production environment. Commented Mar 9, 2021 at 19:39
  • does any one have a solution for AKS Commented Mar 17, 2022 at 14:07
  • stackoverflow.com/q/62376063/4393351 Commented Jun 28, 2022 at 8:35

39 Answers 39

86

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.

Sign up to request clarification or add additional context in comments.

3 Comments

oh man, your frist paragraph saved me~! I realized that the reason why the swagger.json was not there was because that there were some errors in my API Controller which prevented the swagger to generate the json file. Once I fixed all errors, the swagger UI was back~! By looking into the url points to swagger.json, it throws errors which is really helpful for fixing the issue!!!
I had the same issue, One of my delete endpoints is not completely implemented and uses Route attribute. Once I changed the Route attribute to HttpDelete for that endpoint, the error is gone. Thanks @Marisol
In addition, the error might not actually show up in your browser. Run your application in debug mode, and turn on breaking on all CLR exceptions. When you load the swagger.json URL, the exception will be thrown and shown to you. This should contain the details of why the swagger.json file isn't being generated.
73

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:

enter image description here

14 Comments

I actually had the app.UseSwagger above the env.IsDevelopment line, but I moved it into that section and added the app.UseSwaggerUI. Same issue. No output still. I updated my question to reflect the new code.
Now I am also bugged. I dont know if it actually creates a file, or if it just generates the json on the fly and dont save it.
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"); });
Thanks @2b77bee6-5445-4c77-b1eb-4df3e5; that worked perfectly for me.
@Eru Glad it was helpful, I have just added it as an answer
|
56

If your application is hosted on IIS/IIS Express try the following:

c.SwaggerEndpoint("../swagger/v1/swagger.json", "MyAPI V1");

4 Comments

only answer that worked. Thanks a lot. Can you please also elaborate the reason in detail please
This is what solved it for me too. Not sure why though.
Same, exactly what I needed for IIS hosting. I'm guessing the "../" allows for relative URL hosting. Thanks so much!
Typically, this is related to how the site is hosted in IIS. If you're hosting at the site level, you likely won't have this issue, but if you're hosting at an app under a site you likely will see this. The other problem even with the change above is that Swashbuckle may end up showing a server dropdown list on the swagger page, which will just show you one item which will be the name of the app. In this scenario, you can remove it by using the app name in place of the ".." that prefixes the /swagger/..., and adding a DocumentFilter to clear the server list.
38

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");
});

1 Comment

Wow, that seems random. (And it worked in my case, thanks.)
31
#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

1 Comment

it would be better to use the SwaggerUIOptions.RoutePrefix to define the webapi prefix (using a value from the config) rather than having it hardcoded.
28

You must conform to 2 rules:

  1. Decorate all actions with explicit Http Verbs like[HttpGet("xxx")], [HttpPost("xxx")], ... instead of [Route("xxx")].
  2. 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.

3 Comments

for me enough just add [NonAction], with [Route("xxx")]
I'm working on a .NET 5 Controller with OnActionExecuting()/OnActionExecuted() implemented agaisnt IActionFilter, and adding the [NonAction] attribute to those method did the trick for me.
@MohammadBarbast Just for clarification, I used [NonAction] rather than [NoAction] (in your second bullet) because the [NoAction]attribute does not exist in .NET 5 (not sure if you have a typo or it used to exist in previous Core versions and was changed).
17

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.

2 Comments

Same here, Developer tools showed me that the path was pointing to the localhost root as opposed to the specific app under default site
After taking a look at the web console I figured out the document creation was crashing because I had two different entry models with the same name. Thanks for pointing in the right direction mate.
16

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"); });

Comments

10

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.

version name with capital V

2 Comments

Faced with the same problem. I found I used mismatching versions when declaring SwaggerDoc and SwaggerEndpoint configuration. After I fixed versions all started to work fine.
Thanks for this. This is actually the best answer. SwaggerDoc(name) must be the same with value of SwaggerDoc(OpenApi -> Version) & SwaggerEndpoint(url) also. Hence SwaggerUI will route to correct swagger file
8

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

  1. Having public methods in controller without HTTP method attributes

  2. Having multiple methods with same Http attributes which could map to same api call if you are not using "[action]" based mapping

  3. 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)

1 Comment

I had two HTTPGET's, different signatures but once I removed my new one my error went away.
8

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.

1 Comment

Oh that stings...! My exact problem.
6

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);
}

1 Comment

I had a controller without HttpMethod attribute (HttpGet, HttpPost etc) attributes on the methods that caused swagger to fail with Actions require an explicit HttpMethod binding for Swagger
6

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");

Comments

5

Adding a relative path worked for me:

app.UseSwaggerUI(c =>
{
    c.SwaggerEndpoint("../swagger/v1/swagger.json", "My App");
});

Comments

2

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>

Comments

2

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
    {
    }
}

Comments

2

Try to follow these steps, easy and clean.

  1. Check your console are you getting any error like "Ambiguous HTTP method for action. Actions require an explicit HttpMethod binding for Swagger 2.0."
  2. 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)

  1. If NO. Please let us know your issue and solution if you have found any.

1 Comment

In my case I missed the annotation for the put method [HttpPut], Swashbuckle fails ugly and doesn't give an explanation about the error. Thanks Unicoder.
2

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

Comments

1

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.

enter image description here

1 Comment

On top of this, if you don't get an exception back, but just a 500 error, you may still be getting an exception that's hidden. When running in debug mode turn on all CLR errors, and you should be able to find the details of the error.
1

Also I had an issue because I was versioning the application in IIS level like below:

enter image description here

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");
});

Comments

1

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" });
});

Comments

1

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.

Swagger Enable UI

Comments

1

You might forgetting to include.. StartUp.cs/Configure()

app.UseSwagger();

Check if you forgot to include, you error must be remove.

Comments

1

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.

Comments

1

maybe you have duplicate route in one api!

Comments

0

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

Comments

0

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":

enter image description here

Comments

0

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 - ...
...
...

Comments

0

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

Comments

0

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 :)

Comments

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