Add an upload button to your swagger page

The swagger adventures continue…

In .NET Core the current recommended way to upload a file in ASP.NET is with an IFormFile.

If you’re using an IFormFile in your ASP.NET Web Api like so:

public IActionResult UploadFile(IFormFile file)

If you do this, the Swagger page as rendered by Swashbuckle won’t look correct:

However, if you install version 2.5.0 or later of my Swashbuckle.AspNetCore.Examples NuGet package, then you can add the [AddSwaggerFileUploadButton] attribute to your controller action, like so:

public IActionResult UploadFile(IFormFile file)

and then enable my filter in your Startup.cs:

services.AddSwaggerGen(c =>

Then you’ll get a nice upload button:


Speed up development in a NuGet package-centric solution

As microservices architectures become more popular, so increases usage of NuGet as a way of sharing code amongst separate services. The last few projects I’ve worked on have typically contained a number of “Core” NuGet packages with shared code and interfaces that are consumed by one or more services in the solution. Our build pipeline will publish these NuGet packages to an in-house NuGet server.

This can cause a lot of developer friction when you’re working in one of the services and you decide you need to change one of the Core projects. Typically you’ll

  1. make the change to Core
  2. commit it
  3. (Perhaps raise a PR and wait for approval)
  4. wait for the build to publish new versions of the package
  5. and finally updated the package in your service.

Probably at least 20 min wait for all that to happen. And then you realise that your change didn’t quite work, so you have to go through the cycle again with another change.

Well, here’s a shortcut to that cycle and it’s pretty darn simple. Note that this only works if you’re using the newer .NET Core style .csproj containing <PackageReference>. Simply

  1. make the change in Core and compile it locally
  2. Copy the resulting dll(s) to your local NuGet packages feed folder. NOT the bin folder of your service, or the packages folder of your service. On my machine the local NuGet packages feed folder is C:\Users\matt\.nuget\packages\.

As soon as the dll is copied, Visual Studio detects the change – you don’t need to tell it to update the NuGet packages or even compile!

Another surprise bonus of this – while debugging you can step into the Core code! You don’t need to mess around copying PDBs around or anything. I don’t know how it works, but Visual Studio seems to somehow know that the DLL you’ve copied into the NuGet folder came from your local machine and thus it knows where the source code for it is.

Obviously once you’re happy that your changes to Core are working correctly, then you can can commit them and consume an updated version of the package in your service as usual.

Anyway, hopefully this will speed up your local development as much as it has mine.

How to include Swashbuckle .xml files in your Service Fabric project

If you’re using Swashbuckle’s IncludeXmlComments() option, then your build needs to output an XML file containing the various comments.

By default, the XML file will not be included in your Service Fabric deployment. To get it to work, one way is to add the following section to your Web project’s .csproj:

  <Target Name="PrepublishScript" BeforeTargets="PrepareForPublish">
      <DocFile Include="bin\x64\$(Configuration)\$(TargetFramework)\win7-x64\*.xml" />
    <Copy SourceFiles="@(DocFile)" DestinationFolder="$(PublishDir)" SkipUnchangedFiles="false" />

You should also make sure that your xml file is output for all of these different build configurations, again in your Web project’s .csproj:

  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">

  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">

  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|AnyCPU'">

  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'">

Thanks to vdevappa’s comment here

Run a Service Fabric solution locally without deploying to Service Fabric

This is a similar piece to another post of mine from a few years ago Run a Windows Azure cloud service locally without the Azure compute emulator

So you’re working on a Service Fabric application which has an ASP.NET Web api host project. I find the debugging experience painful, for two reasons:

  1. Time to start debugging the project is a minimum of 45 seconds, every time, because the app gets deployed to a local service fabric cluster which takes forever.
  2. You need to remember to run Visual Studio as administrator in order for the above local deployment to succeed.

If either of these things bug you, then here’s a possible solution. Once we’re done you’ll be able to set the Web project in your solution as the StartUp project instead of the Service Fabric application, for much faster debugging, and you’ll no longer need to run VS as admin.

First, change the Program.cs in the Web project:

private static void Main()
	if (UseServiceFabric())

private static bool UseServiceFabric()
	var webHostBuilder = new WebHostBuilder();
	var environment = webHostBuilder.GetSetting("environment");

	return environment != "Development";

private static void StartWebHost()
	var builder = new WebHostBuilder()

	var host = builder.Build();

private static void StartServiceFabric()
		// The ServiceManifest.XML file defines one or more service type names.
		// Registering a service maps a service type name to a .NET type.
		// When Service Fabric creates an instance of this service type,
		// an instance of the class is created in this host process.

			context => new WebHost(context)).GetAwaiter().GetResult();

		ServiceEventSource.Current.ServiceTypeRegistered(Process.GetCurrentProcess().Id, typeof(Web1).Name);

		// Prevents this host process from terminating so services keeps running. 
	catch (Exception e)

If the ASPNETCORE_ENVIRONMENT setting is Development, then it won’t use Service Fabric at all and will just use a plain ol’ ASP.NET Core WebHostBuilder to start the web host.

You’ll also need to change your Debug target to be the Web project, instead of IISExpress, via the VS Standard toolbar.

And just like that the app startup time has shrunk from around 40 seconds to around 5 seconds. Or from an unbearable 100 seconds for the application the team I just joined is working on.

Add an authorization header to your swagger-ui with Swashbuckle

Out of the box there’s no way to add an Authorization header to your API requests from swagger-ui. Fortunately (if you’re using ASP.NET), Swashbuckle 5.0 is extendable, so it’s very easy to add a new IOperationFilter to do it for us:

public class AddAuthorizationHeaderParameterOperationFilter : IOperationFilter
    public void Apply(Operation operation, SchemaRegistry schemaRegistry, ApiDescription apiDescription)
        if (operation.parameters != null)
            operation.parameters.Add(new Parameter
                name = "Authorization",
                @in = "header",
                description = "access token",
                required = false,
                type = "string"

Now all you need to do is register it in your EnableSwagger call:

    .EnableSwagger(c =>
        c.SingleApiVersion("v1", "Commerce Services - Discounts");

        foreach (var commentFile in xmlCommentFiles)

    .EnableSwaggerUi(config => config.DocExpansion(DocExpansion.List));

Once that’s done it’ll give you an input field where you can paste your Authorization header. Don’t forget to add the word “bearer” if you’re using a JWT token:

Edit: I wrote this more than a year ago using Swashbuckle 5.2.1, it may not work with later versions.

Generating Swagger example requests with Swashbuckle

This is a follow on from my post from last year about Generating example Swagger responses.

Update May 4th 2017: I have created a new NuGet package called Swashbuckle.Examples which contains the functionality I previously described in this blog post. The code lives on GitHub.

I have also created a .NET Standard version of the NuGet package at Swashbuckle.AspNetCore.Examples, which is also on GitHub.

It can also be useful to generate example requests, and in this post I will show you how.

First, install my Swashbuckle.Examples NuGet package.

Now decorate your controller methods with the included SwaggerRequestExample attribute:

[SwaggerRequestExample(typeof(DeliveryOptionsSearchModel), typeof(DeliveryOptionsSearchModelExample))]
[SwaggerResponse(HttpStatusCode.OK, Type = typeof(DeliveryOptionsModel), Description = "Delivery options for the country found and returned successfully")]
[SwaggerResponseExample(tHttpStatusCode.OK, typeof(DeliveryOptionsModelExample))]
[SwaggerResponse(HttpStatusCode.BadRequest, Type = typeof(ErrorsModel), Description = "An invalid or missing input parameter will result in a bad request")]
[SwaggerResponse(HttpStatusCode.InternalServerError, Type = typeof(ErrorsModel), Description = "An unexpected error occurred, should not return sensitive information")]
public async Task<IHttpActionResult> DeliveryOptionsForAddress(DeliveryOptionsSearchModel search)

Now implement it, in this case via a DeliveryOptionsSearchModelExample (which should implement IExamplesProvider), which will generate the example data. It should return the type you specified when you specified the [SwaggerRequestExample].

public class DeliveryOptionsSearchModelExample : IExamplesProvider
    public object GetExamples()
        return new DeliveryOptionsSearchModel
            Lang = "en-GB",
            Currency = "GBP",
            Address = new AddressModel
                Address1 = "1 Gwalior Road",
                Locality = "London",
                Country = "GB",
                PostalCode = "SW15 1NP"
            Items = new[]
                new ItemModel
                    ItemId = "ABCD",
                    ItemType = ItemType.Product,
                    Price = 20,
                    Quantity = 1,
                    RestrictedCountries = new[] { "US" }

Don’t forget to enable the ExamplesOperationFilter when you enable Swagger, as before:

    .EnableSwagger(c =>

Now that we’ve done all that, we should see the examples output in our swagger.json file, which you can get to by starting your solution and navigating to /swagger/docs/v1.


And the best part is, when you’re using swagger-ui (at /swagger/ui/index), now when you click the example request in order to populate the form, instead of getting an autogenerated request like this:


You’ll get your desired example, like this:


I find that having a valid request on hand is useful for smoke testing your API endpoints are working correctly.

Azure Emulator not working with SQL server alias

I just spent a few hours trying to figure out something that had me stumped.

In my local dev environment I’m building a web api which has a SQL database. The connection string for the database is an alias with a named pipe. If I set the web api as StartUp project in Visual Studio it works fine. (See this post for some tips on how to do that). But when I’d instead start the Azure emulator as the StartUp project it wouldn’t connect to the sql server, with the good ol’:

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 – Error Locating Server/Instance Specified)

Eventually I figured it out. The alias was the problem, because if I changed the connectionstring to .\sqlexpress it worked fine.

Digging deeper, the problem was I had set up the alias on the “SQL Native Client 11.0 Configuration (32bit)” node, but I hadn’t added an alias on the “SQL Native Client 11.0 Configuration” node. So the fix was to create an additional Alias on the “SQL Native Client 11.0 Configuration” node.


So it seems that debugging a web api locally may be a 32 bit process but debugging with the Azure emulator is a 64 bit process. Maybe?

Anyway, hope this helps someone.