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)

I get notifications about this question from time to time and it warms my heart to see how far swashbuckle has come with .net web api's now. From it's infancy in pre-release .net core to now a standard inclusion in .net 6. — dr b, Mar 19 '22 at 16:36
This is still helpful in 2023 with .NET 7. Preventing lots of headaches — Carlos Muñoz, Jun 23 '23 at 20:33

score 268 · Answer 1 · edited Jan 23 '20 at 02:48

268

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:

edited Jan 23 '20 at 02:48

Ryan Leach

4,262
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answered Oct 15 '18 at 09:23

Zin Min

3,898
1
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27

That's the perfect way to find out what is really the problem. Thanks so much! – Machado Dec 06 '18 at 17:29
5

Wish I could upvote this more. There's loads of posts about this on the net, generally with guesses as to what the problem is rather than suggestions on how to debug. This method of debugging is actually all I wanted to know. – David Bridge Nov 29 '19 at 12:09
2

Not working for me. Clicking on link or going to address gave me error 500. – ohdev Apr 14 '20 at 22:03
4

@ohdev Check the order of the middleware pipeline. If UseSwagger comes before any kind of exception handling/logging, that could cause any errors to not be logged – Sangman May 12 '20 at 09:03
1

@Sangman Thanks. I got solution at another comment and I just simply had to change method access qualifier from my controller from public to protected. That's all. Swagger is expecting request type attribute (HttpPost, HttpGet and so on) for every public method in controller. – ohdev May 13 '20 at 08:33
2

Another quick way is to goto chrome debugger-> network tab-> preview. You will get the stack trace for the error. – Dragonknot Jul 29 '20 at 10:47
1

Thanks god I didn't jump out of window before seeing your answer – WSK Dec 10 '21 at 16:24
Using dotnet 6 in 2022, and this is still relevant. Thank you! – danijeljw-RPC Nov 13 '22 at 11:26
This worked for me, but I also turned on all exceptions and disabled 'just my code' in the Visual Studio debugging options and the exeption popped up. – Simon Stanford Feb 19 '23 at 16:50
thanks @Zin Min. Not of the anther answered really helped. In my case, I had 2 mondels that had the same name. I would have never figured that out – H20rider Jun 30 '23 at 16:25

score 205 · Accepted Answer · edited Sep 14 '22 at 20:59

205

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}")]"

edited Sep 14 '22 at 20:59

Abdou Mustafa

3
2

answered Aug 16 '16 at 07:30

hsop

3,546
3
20
19

15

Where do you get the stack trace? I just get the 500 error in my web client without further information. The server does not throw an exception. – Stiefel Jan 16 '18 at 10:16
2

The error message and stacktrace occured when opening the API's Swagger documentation site, i.e. https://myapi.somedomain.com/help/index – hsop Feb 08 '18 at 13:20
2

Thanks, I my case it was NoAction method – Priyesh Kumar Jun 14 '18 at 11:58
2

if method should not be added to swagger, you can make it protected – razon Jul 09 '18 at 07:28
2

Swagger really should handle this with a custom error. – Sellorio Dec 10 '18 at 01:15
One more , it turned one of the POST action method has invalid parameters – Srikanth Apr 27 '19 at 19:02
Thanks, it really worked for me after 2 hours of research. In my case, I missed out [HttpGet] Attribute on the Controller Action Method level. – Rajashekhar Reddy Jul 25 '19 at 09:33
In my case was because I created two methods with same route by mistake – Sales Lopes Jan 27 '20 at 10:27
In my case, I had given a duplicate Route – Guru Pasupathy Oct 20 '20 at 13:39
2

Damn why swagger is still so raw and unpolished, this is very basic stuff :C – AgentFire Dec 17 '20 at 13:16
You saved me. In my case, I was duplicating the [HTTPGet] attribute at a controller. – Shammie Jun 02 '21 at 16:52
I added a private method to my controller but declared it public by mistake. A slightly different flavor of: public-method + no-http-attribute = .net-swagger-bombs – Dudeman3000 Aug 15 '21 at 04:40
Can't believe, swagger crashes if one out of thousand methods is not according to it's expectations? – WSK Dec 10 '21 at 16:20

Mike Gledhill · Answer 3 · 2018-08-14T08:57:32.637

23

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.)

edited Aug 14 '18 at 08:57

answered May 22 '18 at 15:09

Mike Gledhill

27,846
7
149
159

1

In my case, public method from my BaseController should have change from public to protected. But your method was inspiration for me. – ohdev Apr 14 '20 at 22:25
It took me so long to find this solution – Tassisto Jan 19 '22 at 16:00
In my case I was inheriting a BaseController which had some methods without this attribute. Adding this attribute solved my problem. – Felipe Rugai Feb 23 '22 at 19:29

Popa Andrei · Answer 4 · 2022-11-02T09:54:49.263

11

Firstly you can enable the 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.

edited Nov 02 '22 at 09:54

answered Oct 02 '17 at 15:00

Popa Andrei

2,299
21
25

This fixed it for me – rfcdejong Feb 01 '18 at 15:44
2

uninstall/reinstall Swashbuckle.AspNetCore doesnt work for me – Syaiful Nizam Yahya Mar 09 '18 at 05:03
I had followed the directions from http://www.talkingdotnet.com/add-swagger-to-asp-net-core-2-0-web-api/ but for an API that I was upgrading from Core 1.1. Adding Microsoft.AspNetCore.StaticFiles worked from me. – Stephen McDowell Mar 11 '18 at 13:00
Cause for the error can be different in different cases. So, it is must to understand the root cause of the issue. fix might be simpler like in my case. Adding app.UseDeveloperExceptionPage(); in Configure() of start up helped me identify root cause and the fix was really simple – Anusha M Shetty Sep 08 '22 at 03:21
`app.UseDeveloperExceptionPage();` doesn't make any difference for me. I keep getting the same useless page – Alexandre M Jul 25 '23 at 01:01

score 7 · Answer 5 · answered Dec 06 '19 at 09:46

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):

score 7 · Answer 6 · answered May 25 '21 at 22:18

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.

Thanks for this one, took me 40min to find the error. Because there is no exception in the output. — Zar, Aug 31 '21 at 10:47

Mazz Ebra · Answer 7 · 2021-09-01T20:25:44.607

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.

edited Sep 01 '21 at 20:25

answered Aug 31 '21 at 23:08

Mazz Ebra

119
1
7

1

Thanks, this took 30 min of googling to find the right answer :) – Cine Jan 10 '22 at 06:22

M Komaei · Answer 8 · 2022-05-14T10:19:58.680

4

Add [HttpGet] or [HttpPost] on top of api actions.
Add [Reout("YourApiActionName")] on top of api actions ,

or add [Route("[controller]/[action]")] on top of your Controller class.

edited May 14 '22 at 10:19

answered May 14 '22 at 09:54

M Komaei

7,006
2
28
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score 2 · Answer 9 · answered Mar 07 '20 at 16:52

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.

score 2 · Answer 10 · answered Jan 15 '23 at 14:30

2

Might you've missed adding API verb to an endpoint. Can use below header as your need

1.[Microsoft.AspNetCore.Mvc.HttpGet]
2.[Microsoft.AspNetCore.Mvc.HttpPost]

answered Jan 15 '23 at 14:30

dilipkumar1007

329
4
22

score 1 · Answer 11 · answered Sep 13 '17 at 15:04

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!

score 1 · Answer 12 · answered Oct 17 '18 at 22:59

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")].

score 1 · Answer 13 · answered Dec 05 '18 at 16:21

1

in some cases, the router of controller is duplicated. Review the last controller modified.

answered Dec 05 '18 at 16:21

Michelle Rodrigues

61
3

You need review and check router's controllers...after this, build and run again. This is only a suggestion. In my case, this solved my problem... – Michelle Rodrigues Dec 07 '18 at 01:38

Ramil Aliyev 007 · Answer 14 · 2020-05-29T09:18:06.020

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.

score 1 · Answer 15 · answered Mar 15 '21 at 19:58

1

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

answered Mar 15 '21 at 19:58

Vinícius Beloni

11
1

samy nathan · Answer 16 · 2023-02-20T09:17:47.010

1

This came because you have a no-action method on your controller class check that missed an HTTP attribute on any of the controller action methods. If you need a no-action or no need for access from external methods declaration then make it private, you will fix this issue.

private void MyMethod() {

}

edited Feb 20 '23 at 09:17

answered Feb 20 '23 at 06:36

samy nathan

51
6

This one was my case thanks – Samuel B. Jul 24 '23 at 20:41

score 0 · Answer 17 · answered Oct 15 '18 at 14:28

0

When I Add the parameter Version , it works

services.AddSwaggerGen(options =>
        {
            options.SwaggerDoc("v1", new Info { Title = "My API", Version = "v1" });
        });

answered Oct 15 '18 at 14:28

Mohammed Eyad Fakhanee

13
3

score 0 · Answer 18 · answered Nov 26 '18 at 04:05

Also had this problem. In my case, it was caused by two endpoints in the same controller with the same route and method name (but different parameter types). Of course, it then became apparent that that was probably poor practice anyway so I changed the endpoint names and all was well.

score 0 · Answer 19 · answered Feb 20 '19 at 21:54

I was getting this error because in STARTUP.CS I not put the version's name in SwaggerDoc parameters:

Error => c.SwaggerDoc("", blablabla

WORK => c.SwaggerDoc("v1",blablabla

then, now are ok fine!

services.AddSwaggerGen(c => 
    {
c.SwaggerDoc("v1", new Swashbuckle.AspNetCore.Swagger.Info {Title = "PME SERVICES", Version = "v1"});
            });

score 0 · Answer 20 · answered Mar 07 '19 at 19:05

I ran into this issue today configuring Swagger in a .Net Core 2.2 Web Api project. I started down the path that @Popa Andrei mentions above by including the Microsoft.AspNetCore.StaticFiles dependency in my project as I figured that was most likely the culprit. That turned into a rabbit hole of chaining dependencies although it did ultimately work for me.

I then realized that in my ConfigureServices method in Startup I had services.AddMvcCore(...) which just gives you bare bones and you add dependencies as you need them. When I changed that to services.AddMvc(...) it started working without having to manually add all the dependencies required by Microsoft.AspNetCore.StaticFiles.

That doesn't mean you can't take the route of staying with services.AddMvcCore(...) and then adding all the necessary dependencies. You can, and it will work.

It is just much easier to take the services.AddMvc(...) approach and be done.

Hope that helps someone.

score 0 · Answer 21 · answered Mar 09 '19 at 02:50

Making sure my swagger versions lined up with each other fixed my issue. Since I was starting a new project I set my api version to be v0.1

services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v0.1", new Info { Title = "Tinroll API", Version = "v0.1" });
});

But had left my swagger url to be v1.

app.UseSwaggerUI(c =>
{
    c.SwaggerEndpoint("/swagger/v1/swagger.json", "Tinroll API v0.1");
    c.RoutePrefix = string.Empty;
});

I updated my versioning to be /swagger/v0.1/swagger.json instead of v1 and Swagger worked as expected.

score 0 · Answer 22 · edited Mar 25 '19 at 09:13

Since I don't see the solution which worked for me posted here, I will contribute one to the ongoing thread. In my case, it was the Route attribute was set separately with the HttpPost/HttpGet at the function level (not controller level).

INCORRECT:

[HttpPost]

[Route("RequestItem/{itemId}")]

CORRECT:

[HttpPost("RequestItem/{itemId}")]

Also, the Swagger seems to expect Ok(object) result instead of StatusCode(object) result for a success request to return.

score 0 · Answer 23 · answered Apr 20 '19 at 17:36

0

For me it was because of having two class types with the same name but with different namespaces, which are used as the return type of two different actions in different controllers!

When I changed the name of one of them, the problem solved!

answered Apr 20 '19 at 17:36

Majid

3,128
1
26
31

score 0 · Answer 24 · answered May 31 '19 at 09:13

0

For me the problem was due to OData. If I just commented out my services.AddOData(); I didn't get any error.just comment out the services.AddOData();

answered May 31 '19 at 09:13

shishir

1
2

score 0 · Answer 25 · answered Dec 21 '20 at 16:01

If you use Swagger, which is enabled by default in .Net Core 5, it needs to know something about your methods. Normally, you don't need to add [HttpGet] attribute because it is the default HttpMethod for your methods, but swagger requires that information to generate documentation of your code.

So adding [HttpGet] above my method solved my issue.

score -1 · Answer 26 · answered Mar 04 '16 at 15:47

-1

Give a look at this project. https://github.com/domaindrivendev/Ahoy/tree/master/test/WebSites/Basic

This repo is from Swashbuckle´s owner, is a basic ASP.NET 5 Sample app, this is help you to correct configure yours middlewares (and take care about the orders of them, it´s matter, e.g., use "app.UseSwaggerGen();app.UseSwaggerUi(); after app.UseMvc();)

To enable logging in your applcation give a look at: https://docs.asp.net/en/latest/fundamentals/logging.html?highlight=logging (the log will be generated inside "wwwroot" folder

answered Mar 04 '16 at 15:47

Richard Lee

2,136
2
25
33

I tried to get this working with the project i really wanted to add swashbuckle to but it just won't work. I think there may be something in the controller routes that's causing it to get hung up. Following the above i was able to add it to a new .net project with no issues. The issue i'm running into is definitely project specific. Will mark as accepted answer and if i can ever figure out which specific routes are causing the issue i will update the original question. Thanks! – dr b May 19 '16 at 13:30

ddagsan · Answer 27 · 2018-11-05T06:27:01.320

-1

To see the source of exception

open chrome browser
open developer tools
see exceptions in console tab
fix it.

edited Nov 05 '18 at 06:27

answered Nov 05 '18 at 06:17

ddagsan

1,786
18
21

It would be better if you give a proper explanation instead of asking us to go to console ! – Sagar Khatri Dec 19 '18 at 11:45
You're right. I tried to explain that there is no specific solution about it. The source of problem might be in console message. – ddagsan Mar 05 '19 at 10:40

score -2 · Answer 28 · answered Jun 09 '16 at 15:56

The setup for Swagger is varying greatly from version to version. This answer is for Swashbuckle 6.0.0-beta9 and Asp.Net Core 1.0. Inside of the ConfigureServices method of Startup.cs, you need to add -

 services.AddSwaggerGen(c =>
    {
      c.SingleApiVersion(new Info
      {
        Version = "v1",
        Title = "My Awesome Api",
        Description = "A sample API for prototyping.",
        TermsOfService = "Some terms ..."
      });
    });

Then in the Configure method you must add -

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
    loggerFactory.AddConsole(Configuration.GetSection("Logging"));
    loggerFactory.AddDebug();

    app.UseMvc();
    app.UseSwaggerGen();
    app.UseSwaggerUi();
}

Be sure you are referencing in Startup.cs -

using Swashbuckle.SwaggerGen.Generator;

My project.json file looks like -

"dependencies": {
    "Microsoft.AspNetCore.Mvc": "1.0.0-rc2-final",
    "Microsoft.AspNetCore.Server.IISIntegration": "1.0.0-rc2-final",
    "Microsoft.AspNetCore.Server.Kestrel": "1.0.0-rc2-final",
    "Microsoft.EntityFrameworkCore.SqlServer": "1.0.0-rc2-final",
    "Microsoft.EntityFrameworkCore.SqlServer.Design": "1.0.0-rc2-final",
    "Microsoft.EntityFrameworkCore.Tools": "1.0.0-*",
    "Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0-rc2-final",
    "Microsoft.Extensions.Configuration.FileExtensions": "1.0.0-rc2-final",
    "Microsoft.Extensions.Configuration.Json": "1.0.0-rc2-final",
    "Microsoft.Extensions.Logging": "1.0.0-rc2-final",
    "Microsoft.Extensions.Logging.Console": "1.0.0-rc2-final",
    "Microsoft.Extensions.Logging.Debug": "1.0.0-rc2-final",
    "Swashbuckle": "6.0.0-beta9"
  },

  "tools": {
    "Microsoft.AspNetCore.Server.IISIntegration.Tools": {
      "version": "1.0.0-preview1-final",
      "imports": "portable-net45+win8+dnxcore50"
    },
    "Microsoft.EntityFrameworkCore.Tools": {
      "version": "1.0.0-preview1-final",
      "imports": [
        "portable-net45+win8+dnxcore50",
        "portable-net45+win8"
      ]
    }
  },

  "frameworks": {
    "net452": { }
  },
  "buildOptions": {
    "emitEntryPoint": true,
    "preserveCompilationContext": true,
    "xmlDoc": false
  },

  "publishOptions": {
    "include": [
      "wwwroot",
      "Views",
      "appsettings.json",
      "web.config"
    ]
  },

  "scripts": {
    "postpublish": [ "dotnet publish-iis --publish-folder %publish:OutputPath% --framework %publish:FullTargetFramework%" ]
  }
}

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

28 Answers28

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