[c#] 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.

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

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

#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

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");
});

You must conform to 2 rules:

1. Decorate all actions with explicit Http Methods like[HttpGet("xxx")],[HttpPost("xxx")] or ... 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.

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"); });

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)

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);
}

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.

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.

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)

3. 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

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.

Adding a relative path worked for me:

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

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");

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":

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

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 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 => 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 ,

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.

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

app.UseSwagger();

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

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

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 =>
{
c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
c.RoutePrefix = string.Empty;
});

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 - ...
...
...

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://docs.microsoft.com/en-us/aspnet/core/tutorials/getting-started-with-swashbuckle?view=aspnetcore-3.1&tabs=visual-studio

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.

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 :)

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.

// Enable middleware to serve generated Swagger as a JSON endpoint.

app.UseSwagger(c =>
{
    c.SerializeAsV2 = true;
});

// Enable middleware to serve swagger-ui (HTML, JS, CSS, etc.),
// specifying the Swagger JSON endpoint.
app.UseSwaggerUI(c =>
{
    c.SwaggerEndpoint("/swagger/v1/swagger.json", "API Name");
});