This overview is an introduction to the concepts, and covers what you need to get started. There is more detailed documentation in the links from this page about all of the options available for configuring the Owin pipeline and the middleware components.

Microsoft OWIN

The Owin Framework is built on Microsoft OWIN. The way that Microsoft OWIN works is by chaining middleware into a pipeline, then passing each http request through the pipeline until one of the middleware chooses to handle the request and return a response.

In the Microsoft world the application developer constructs a pipeline of middleware components using code that looks like this:

public void Configuration(IAppBuilder app)
   app.Use(new Middleware1())
      .Use(new Middleware2())
      .Use(new Middleware3())
      .Use(new Middleware4());

Owin Framework

This Owin Framework contains middleware that can be added to the Owin pipeline, and internally implements a richer middleware definition that adds:

  • Adding middleware the the pipeline
  • Providing information about how the middleware is configured
  • Defining dependencies between middleware
  • Spliting the OWIN pipeline into a tree of routes rather than a linear list

For a more complete description of how all of this works, see the Owin Framework Conceptual Overview.

When using the Owin Framework, the application code for setting up the middleware pipeline looks like this example:

public void Configuration(IAppBuilder app)
  var builder = new Builder();

  builder.Register(new NotFoundError())
    .ConfigureWith(configuration, "/owin/notFound/staticFiles");

  builder.Register(new FormsIdentification())
    .ConfigureWith(configuration, "/owin/auth/forms");


Note that the app.Use(builder); line at the end is calling the extension method that is defined by the Microsoft OWIN assembly. The code above that is specific to the Owin Framework.

Note that each middleware that is added to the Builder has fluent syntax for defining the configuration provider and the path within the configuration file to the configuration data for that middleware.

Note that each middleware can be named, and these names can be used to define dependencies. The Builder will add them to the Owin pipeline in an order that satisfies these dependencies.

Configuring Middleware

The Owin Framework provides a simple standardization of middleware configuration so that:

  • Application developers can choose any method they like to provide configuration to the middleware in their application, and are not restricted to everything being in a web.config file. For example they can use the Urchin centralized rules-based configuration management system instead of web.config if they like.
  • Applications define the layout of their configuration data and can therefore include multiple instances of the same middleware with different configurations. This is in contrast to the Microsoft approach where each component defines where it's configuration data is located in the web.config file which makes it impossible to have two instances of the same component with different configurations.
  • Middleware developers do not need to know or care which configuration mechanism the application developer chose.
  • All configuration data is strongly typed using simple class definitions. Middleware developers define the shape of the configuration data and the default values. Application developers define the layout of their configuration data as a whole and selectively override the default values.
  • It is possible to write unit tests that test different configurations by mocking the configuration data provider.
  • Middleware that can be configured can implement the optional IConfigurable interface.
  • Application developers configure the middleware in their application by using the fluid .ConfigureWith() method when adding middleware to the pipeline builder. The ConfigureWith() method is passed an object that implements the IConfiguration interface. The Owin Framework provides implementations of this interface for getting configuration data from web.config and for Urchin. This is a very simple interface that you can easily implement yourself to get configuration data from your database or any other source.

Configuration Options

How to use Urchin as a configuration provider

How to use the web.config file for configuration data

NuGet package configurations

For details of how to configure specific NuGet packages see the author's documentation for their package. In general Owin Framework middleware packages will have a Configuration class within the source code that is deserialized from the JSON configuration file. You can look at this source code to determine the definitive list of properties that can be configured.

The Index of NuGet packages has links the documentation and source code for all Owin Framework NuGet packages.