500 Error when setting up Swagger in asp .net CORE / MVC 6 app

Question

I'm trying to setup a basic swagger API doc in a new asp .net CORE / MVC 6 project and receiving a 500 error from the swagger UI: 500 : http://localhost:4405/swagger/v1/swagger.json

My startup class has the following code in it:

using Swashbuckle.SwaggerGen;
using Swashbuckle.SwaggerGen.XmlComments;
using Swashbuckle.Application;
....
public void ConfigureServices(IServiceCollection services)
{
  ...
  services.AddSwaggerGen();
  services.ConfigureSwaggerDocument(options =>
  {
    options.SingleApiVersion(new Info
    {
        Version = "v1",
        Title = "Blog Test Api",
        Description = "A test API for this blogpost"
    });
  });
}

and then under Configure:

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
....
  app.UseSwaggerGen();
  app.UseSwaggerUi();
....
}

When i build and run the project, the UI will come up when i go to swagger/UI/index.html, but the 500 error above is displayed. When i go to the swagger/v1/swagger.json link, console gives the following 500 error: Failed to load resource: the server responded with a status of 500 (Internal Server Error)

Is there any way i can figure out the root cause of the 500 or enable any additional debug in swagger to figure out why it's throwing this error? Based on some of the tutorials i've looked at, only what i have in startup is required for a base implementation. Please let me know if i can provide any additional information.

EDIT: this is for rc1, and may not be relevant to the new netcore 1.0 currently out (6/29/2016)

Answer 1

Initially I got a 500 error too. Deep down in the stacktrace it said: System.NotSupportedException: Unbounded HTTP verbs for path 'api/hotels'. Are you missing an HttpMethodAttribute?

It turned out I was missing a HttpGet attribute for one of my api methods:

[Microsoft.AspNetCore.Mvc.HttpGet]

also if you used a method with a parameter like this "Get(int id)" you will get the same error without an explanation so you need to add it into the decoration "[HttpGet("{id:int}")]"

Answer 2

If someone want to know the exact error is in the Swagger's stack trace, request the URL:

<your-app-url>/swagger/v1/swagger.json 

Or, click on the swagger.json link from the browser dev tools console:

Which will show the error in your IDE Output:

Answer 3

I got this error when one of my functions was marked as public, but wasn't meant to be a web service which could be called directly.

Changing the function to private made the error go away.

Alternatively, immediately before your public function, you can put the [NonAction] command, to tell Swagger to ignore it.

[NonAction]
public async Task<IActionResult> SomeEvent(string id)
{ 
   ...
}

(I wish Swagger would actually report the name of the function which caused this problem though, rather than just complaining that it could no longer find the "../swagger/v1/swagger.json" file... that's not particularly useful.)

Answer 4

Firstly you can enable de developer exception page by adding app.UseDeveloperExceptionPage(); on your Configure() in order to see better which is the root cause. Take a look here

In my case the problem was that I have to install also Microsoft.AspNetCore.StaticFiles nuget in order to make Swagger work.

Try also to uninstall/reinstall Swashbuckle.AspNetCore nuget.

Answer 5

I had this problem today and the cause was that some methods on my controllers API was missing [HttpGet]:

The exception (in stack trace) showed me the problme You can also check the exception in the Output window in Visual Studio like this (in my case it showed me):

Answer 6

Look here if you're not able to load the and look at the swagger.json in the console.

Swagger has a difficult time negotiating the differences between namespaces. When building the objects expected for api calls it will index through each defined class. If there are two classes that share a class name it won't be able to process the swagger.json file.

Example of two classes that .Net will process correctly, but Swagger will not.

namespace MyCompany.PaymentProcessor.DTO
{

    public class Payment
    {
      //dto content
    }
}

and

namespace MyCompany.CbData
{

    public class Payment
    {
       //couch base data
    }
}

Will be treated correctly by .Net, but unresolvable by swagger.

Answer 7

In my case I was missing an action in route attribute which exist in your API controller.

Something like this:

[Route("api/[controller]/[action]")]

Before I had:

[Route("api/[controller]")]

An error occoures when writing [Route("api/[controller]")] because swagger doesn't know how to separate the API methods without action inside your route attribute.

Answer 8

If someone want to know the exact error is in the Swagger's stack trace, request the URL:

<your-app-url>/swagger/v1/swagger.json

Or, click on the swagger.json link from the browser dev tools console:

Which will show the error in your IDE Output:

Answer 9

Had the same problem and the error message helped me identify the root cause:

{
  "error": "Conflicting method/path combination \"POST api/calls\" for actions - SMSApi_v2.Controllers.CallController.CreateCall (SMSApi_v2),SMSApi_v2.Controllers.CallController.CreateCalls (SMSApi_v2). Actions require a unique method/path combination for Swagger/OpenAPI 3.0. Use ConflictingActionsResolver as a workaround"
}

The root were these lines of code:

    **[HttpPost("calls")]**
    public IActionResult CreateCall([FromBody]Call call)
    {
        repository.Create(call);
        return Ok(call);
    }

    **[HttpPost("calls")]**
    public IActionResult CreateCalls([FromBody] string xmlFile)
    {
        var calls = xmlProcessor.DeserializeTo<List<Call>>(xmlFile);
        if (!calls.Any())
            return BadRequest("Deserializing was not done correctly.");

        repository.Create(calls);
        return Ok(calls);
    }

Even if the signatures of the methods are different, the two API verbs have the same route and this is generating the error.

Answer 10

Also if I may add, the swagger set up does not like it when you route at the root level of your controllers. For example:

Do not do this:

[Produces("application/json")]
[Route("/v1/myController")]
[Authorize]
public class myController
{
    [SwaggerResponse((int)System.Net.HttpStatusCode.OK, Type = typeof(RestOkResponse<Response>))]
    [SwaggerResponse((int)System.Net.HttpStatusCode.InternalServerError, Type = typeof(RestErrorResponse))]
    [SwaggerResponse((int)System.Net.HttpStatusCode.BadRequest, Type = typeof(RestErrorResponse))]
    [SwaggerResponse((int)System.Net.HttpStatusCode.Forbidden, Type = typeof(RestErrorResponse))]
    [SwaggerResponse((int)System.Net.HttpStatusCode.NotFound)]
    [HttpPost]
    [Authorize()]
    public async Task<IActionResult> Create([FromBody] MyObject myObject)
    {
        return Ok();
    }
}

Do this:

[Produces("application/json")]
[Authorize]
public class myController
{
    [SwaggerResponse((int)System.Net.HttpStatusCode.OK, Type = typeof(RestOkResponse<Response>))]
    [SwaggerResponse((int)System.Net.HttpStatusCode.InternalServerError, Type = typeof(RestErrorResponse))]
    [SwaggerResponse((int)System.Net.HttpStatusCode.BadRequest, Type = typeof(RestErrorResponse))]
    [SwaggerResponse((int)System.Net.HttpStatusCode.Forbidden, Type = typeof(RestErrorResponse))]
    [SwaggerResponse((int)System.Net.HttpStatusCode.NotFound)]
    [HttpPost("/v1/myController")]
    [Authorize()]
    public async Task<IActionResult> Create([FromBody] MyObject myObject)
    {
        return Ok();
    }
}

It took me a while to figure that the reason why I was getting internal server error was because of this routing issue. Hope this helps someone!

Answer 11

Might be obvious but, besides missing the HttpGet or HttpPost attributes, don't forget to differentiate the post methods.

You may have 2 different methods (with different names) marked with HttpPost, and that would also cause this kind of issue. Remember to specify the method name in the attribute: [HttpPost("update")].

Answer 12

I get same error in ASP.NET Boilerplate. I searched a lot and found a problem with my code. I use same name two DTO object, but located different namespaces.

For example first DTO object is like as below:

namespaces Test{
    public class TestDto
    {
        public int Id{get;set;}
    }
}

And second DTO object is like as below:

namespaces Test_2{
    public class TestDto
    {
        public int Id{get;set;}
    }
}

I changed Test_2.TestDto's name, problem did solve for me after.

Answer 13

In my case, a model has the same name as another model, I fixed changing the name