How to use the autogenerated swagger client

A detailed post on how to use an autogenerated swagger client

This blogpost will focus on the generated C# client.
To get started you basically just need 1 thing.

  1. A Swagger.Json file

Creating the client

If you already have the client you can skip this part
So you have created an API and added Swagger to it or you have been given a swagger.json file or someone else has created a swagger enable API or any combination of the above.
Now you want to create a client for, thankfully http://editor.swagger.io

Can generate a client for you.
Get your swagger.json file (if using swashbuckle the default url for the file is {your api domain}/swagger/docs/v1)
Go the http://editor.swagger.io

swaggerpaste
and paste the swagger.json file into the modal that pops up.
Note:
The editor should notify you of any errors in the schema
For this article I have used the swagger.json from the petstore example (any valid swagger will do).
If no errors arise, you are ready to generate the client.
swaggergenerateclient
Once the zip file is done downloading you should unzip and compile it using the Compile.bat file, located inside the folder.
Once compiled you can find the client and it’s dependencies inside the /bin folder.
Then just add the reference to a new project.
I will be using a basic Console Application.


Using the client

Note: The generated client has 2 dependencies namely; Newtonsoft.Json and RestSharp, these should be referenced through Nuget instead of using the ones that come with the client.
I will provide a basic run-through of how to use the client with different types of authentication, and how to use the generated client.
2 things to note about the client.

  1. All endpoints for the are located in the IO.Swagger.Api namespace
  2. All configuration options for the httpclient is located in the IO.Swagger.Client namespace
    This is where we will provide:

* Authentication
* Default Headers
* UserAgent
* etc.
3. All response models are location in the IO.Swagger.Model namespace
I will start with the configuration as this needs to be out of the way to call the API.

Client Configuration

Authentication:
The examples given are general examples and are not related to the petstore client (apart from the api naming).
I will go through 2 types of Authentication

  1. Basic Authentication
  2. APIKey authentication

Basic Authentication in the generated client is very straightforward

The above example will use the Authorization Header as transport with whatever scheme is defined in the swagger.json file.
Using an APIKey is almost as easy as Basic Authentication:
There are 2 configuration options for apiKey ApiKeyPrefix and ApiKey.
They are both directly related to the header that will be used as transport for the token.

In the above example we are using the Authorization Header as transport and we are using the Bearer Scheme (ApiKeyPrefix)
The sent header will look like the following: Authorization: Bearer {Some token value}

Endpoints

Using the endpoints is almost insanely easy. Every API endpoint is wrapped in a nice easy to use method, with input and output models.
The petstore API uses an api_key header with the value of “special-key” for authentication.
apikeyauth
The code for accessing the store inventory looks as the following

which generates the following output
clientoutput
The code for getting all pets with a particular status (to show the use of output models)

which generates the following output (as of this writing)
Petnames

End

This concludes the post, you should find that using the generated API is pretty straightforward and easy.

Handling Exceptions in WebApi globally

Handling exceptions can be such a hassle. Thankfully the WebAPI pipeline can help alot.
Utilizing the ExceptionFilterAttribute class can create
a consistent and simple way of returning great error responses for your API – like this

Lets get started.

First of all we need:

The Error Model:

The error interface:

We have 4 things here
1. ExceptionType – The type of error
2. A HttpStatusCode – Because returning the statuscode can prove useful to consumers
3. A Code – I use this for the httpstatuscode message
4. A List of Errors
1. Exception Type

Just an enum. I tend to use only Error, but it allows for a more gradient approach if needed.
2. HttpStatusCode
Thankfully the System.Net namespace provides most HttpStatusCodes as enum, so I just utilize this.
3. Code
I use this for the string interpretation of the httpStatusCode, but could be an internal code as well.
4. List of Errors

The above class consists of a Reason phrase and a message to go with this phrase
The “reasons” is also encapsulated as enums, but will be converted into their string representations in the inherited ApiException Class

The derived ApiException Class

Not alot to it. A few constructors, but it should explain itself pretty well.
“All of this is all good and fine, but how do we handle exceptions globally?” you ask.

The GlobalExceptionAttribute


it basically just checks which type of exception was thrown, and acts accordingly, notably typeof(ApiException). Any “unhandled” errors is thrown as “internal server error”. This is also where you would put any logging, as all exceptions will go through this filter. (I have left this out).
The above attribute should be applied in the WebApiConfig.cs file.

As you can see from the following part of the attribute

We check for any errors with typeof(ApiException), but we haven’t implemented the error type yet.
So in any Actions where you would normally return errors, you throw a new ApiException instead.

The above would cause our API to return a response, with a responsecode of 404 and the following body