OwinGlobalAsax

This page explains how to use the NSwag OWIN middleware in your "Global.asax"- based web project. It is recommended to migrate your project to a completely OWIN-based project and use the OWIN middleware directly. The OWIN middlewares will be deprecated eventually and will not receive many bug fixes and new features.

Sample project

Integration

1. Install NuGet packages

Install the NuGet packages:

• Microsoft.Owin.Host.SystemWeb
• NSwag.AspNet.Owin

2. Edit web.config

Then open your Web.config and add the following app setting:

<configuration>
    <appSettings>
        <add key="owin:AutomaticAppStartup" value="false" />
    </appSettings>
    ...

Now we need setup the routing of the Swagger requests. There are two alternative ways to do this:

2.a) Pipe all request to the .NET pipeline

In the system.webServer tag, set runAllManagedModulesForAllRequests to true so that all requests are piped to ASP.NET:

<system.webServer>
	...
	<modules runAllManagedModulesForAllRequests="true">
		...

2.b) Pipe only the Swagger request to the specific middlewares

Important: The routes defined in the web.config and the UseSwagger/UseSwaggerUi methods must be the same:

<system.webServer>
	...
	<handlers>
		...
		<add name="NSwag" path="swagger" verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />

3. Edit Global.asax.cs

Now, open the Global.asax.cs and add the following call at the beginning of the Application_Start method:

public class WebApiApplication : System.Web.HttpApplication
{
	protected void Application_Start()
	{
		RouteTable.Routes.MapOwinPath("swagger", app =>
		{
			app.UseSwaggerUi3(typeof(WebApiApplication).Assembly, settings => 
			{
				settings.MiddlewareBasePath = "/swagger";
        //settings.GeneratorSettings.DefaultUrlTemplate = "api/{controller}/{id}";  //this is the default one
        settings.GeneratorSettings.DefaultUrlTemplate = "api/{controller}/{action}/{id}";
			});
		});
	
		...

Be careful about settings.GeneratorSettings.DefaultUrlTemplate, make sure the DefaultUrlTemplate is the same as you configured in config.Routes.MapHttpRoute, otherwise you will encounter exception as following:

The method 'Post' on path '/api/admin/v/product' is registered multiple times

Now, start the web project and browse to "http:/localhost:port/swagger" and the Swagger UI should be loaded.