ASP NET Core - Swashbuckle not creating swagger json file

Question

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   gt                        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   gt                                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 lt string gt  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

User · Answer

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
    {
    }
}

User · Answer

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  quot  action  quot  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

User · Answer

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

User · Answer

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   gt        c SwaggerGeneratorOptions IgnoreObsoleteActions   true      c SwaggerDoc  v2   new Info   Title    My API   Version    v2

User · Answer

I had a silly issue  I had a capital v in the AddSwaggerGen method and a lowercase v in c SwaggerEndpoint   It appears to be case sensitive

User · Answer

Enable middleware to serve generated Swagger as a JSON endpoint   app UseSwagger c   gt        c SerializeAsV2   true          Enable middleware to serve swagger-ui  HTML  JS  CSS  etc       specifying the Swagger JSON endpoint  app UseSwaggerUI c   gt        c SwaggerEndpoint  quot  swagger v1 swagger json quot    quot API Name quot

User · Answer

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    lt PackageReference Include  Microsoft OpenApi  Version  1 1 4    gt   lt PackageReference Include  Swashbuckle AspNetCore Swagger  Version  5 0 0-rc4    gt   lt PackageReference Include  Swashbuckle AspNetCore SwaggerGen  Version  5 0 0-rc4    gt   lt PackageReference Include  Swashbuckle AspNetCore SwaggerUi  Version  5 0 0-rc4    gt    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   gt                                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   gt                        c SwaggerEndpoint   swagger v1 swagger json    My API V1                  c RoutePrefix   String Empty                       app UseRouting             app UseAuthorization             app UseEndpoints endpoints   gt                        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

User · Answer

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

User · Answer

You must conform to 2 rules   Decorate all actions with explicit Http Methods like HttpGet  quot xxx quot     HttpPost  quot xxx quot    or     instead of  Route  quot xxx quot     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

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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

User · Answer

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   gt    c SwaggerEndpoint  v1 swagger json    API name

User · Answer

You might forgetting to include   StartUp cs Configure   app UseSwagger     Check if you forgot to include  you error must be remove

User · Answer

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   gt        options SwaggerEndpoint   1 0 swagger V1 swagger json    Static Data Service

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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 lt TransactionResult gt  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 lt TransactionResult gt  WipAbort BodyWipStartDTO data        return await  wipServices WipAbort data       This a correct way   HttpPost  Route  Start    public async Task lt TransactionResult gt  WipStart BodyWipStartDTO data        return await  wipServices WipStart data       HttpPost  Route  Abort    public async Task lt TransactionResult gt  WipAbort BodyWipStartDTO data        return await  wipServices WipAbort data

User · Answer

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   gt                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

User · Answer

You actually just need to fix the swagger url by removing the starting backslash just like this   c SwaggerEndpoint  quot swagger v1 swagger json quot    quot MyAPI V1 quot     instead of   c SwaggerEndpoint  quot  swagger v1 swagger json quot    quot MyAPI V1 quot

User · Answer

If your application is hosted on IIS IIS Express try the following   c SwaggerEndpoint     swagger v1 swagger json    MyAPI V1

User · Answer

i had the same Error   but due to different issue  i was using a 3rd party library which cause this issue  and i did not need to have this library in my exposure  so i used the below solution that is posted here    Create somewhere class ApiExplorerIgnores with following content  public class ApiExplorerIgnores   IActionModelConvention       public void Apply ActionModel action                if  action Controller ControllerName Equals  ImportExport                action ApiExplorer IsVisible   false            Add following code to method ConfigureServices in Startup cs  services AddMvc c   gt  c Conventions Add new ApiExplorerIgnores       this will get read of all methods in that controller  you can also use a specific level  like method name or so  also you can remove one Method only  and so one

User · Answer

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

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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

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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

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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   amp  path  api Values  id   overloaded by actions -

User · Answer

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

User · Answer

In my case  I ve had forgotten to set public access modifier for methods

User · Answer

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

User · Answer

Answer   If using directories or application  with IIS or a reverse proxy  lt br  gt  set the Swagger endpoint to a relative path using the    prefix  For example  lt br  gt    swagger v1 swagger json  Using  swagger v1 swagger json instructs the app to lt br  gt look for the JSON file at the true root of the URL  plus the route prefix  if used   For example  use http   localhost  lt br  gt  lt br  gt  lt port gt   lt route prefix gt  swagger v1 swagger json instead of http   localhost  lt br  gt  lt port gt   lt virtual directory gt   lt route prefix gt  swagger v1 swagger json  lt br  gt  if  env IsDevelopment          app UseDeveloperExceptionPage            Enable middleware to serve generated Swagger as a JSON endpoint      app UseSwagger        app UseSwaggerUI c   gt          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   docs microsoft com en-us aspnet core tutorials getting-started-with-swashbuckle view aspnetcore-3 1 amp tabs visual-studio

User · 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

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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

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According to Microsoft  To serve the Swagger UI at the app s root  http   localhost     set the RoutePrefix property to an empty string   app UseSwaggerUI c   gt    c SwaggerEndpoint   swagger v1 swagger json    My API V1    c RoutePrefix   string Empty

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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               lt site name      id  9  gt                 lt application path     applicationPool    gt  lt  application gt                 lt bindings gt  lt  bindings gt              lt  site gt

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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 lt string gt  Get       return new string      quot value1 quot    quot value2 quot           GET api values 5  HttpGet  quot  id  quot    public string Get int id    enter code here    return  quot value quot      Try providing different names in attributes like  HttpGet  quot List quot    public IEnumerable lt string gt  Get      return new string      quot value1 quot    quot value2 quot           GET api values 5  HttpGet  quot ListById  id  quot    public string Get int id      return  quot value quot      This should solve the issue

User · Answer

Adding a relative path worked for me   app UseSwaggerUI c   gt        c SwaggerEndpoint     swagger v1 swagger json    My App

User · Answer

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   gt        swagger SwaggerDoc  quot AppAdministration quot   new Info   Title    quot App Administration API quot   Version    quot v1 0 quot                         app UseSwaggerUI c   gt        c SwaggerEndpoint  quot  swagger AppAdministration swagger json quot    quot App Administration quot

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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

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