title: Generate OpenApi 3 from ApiControllers (C#, .Net 4.5)
body: <p>We are using Swashbuckle to generate a swagger 2.0 json, using C# on Asp .Net 4.5 (not Asp .Net core). I am trying to adapt our solution to generate openApi 3.0:</p>
  
  <ul>
  <li>I understand that Swashbuckle for .Net 4.5 currently does not support openApi 3.0</li>
  <li>I tried using nSwag, but it seems that the openApi that is generated is always 2.0, regardless of using the function UseSwaggerUi3, or using GenerateForControllersAsync with SchemaType = SchemaType.OpenApi3.</li>
  </ul>
  
  <p>Is it supported in nSwag for .Net 4.5? If not, is there any other tool or solution without upgrading to .Net core?</p>
  
  <p>The code I tried with nSwag:</p>
  
  <pre><code>var settings = new WebApiToSwaggerGeneratorSettings
          {
              DefaultUrlTemplate = "api/{controller}/{action}/{id}"
          };
  
          var jsonSettings = new JsonSchemaGeneratorSettings();
          jsonSettings.SchemaType = SchemaType.OpenApi3;
          var schemaGen = new SwaggerJsonSchemaGenerator(jsonSettings);
          var generator = new WebApiToSwaggerGenerator(settings, schemaGen);
          var document = Task.Run(async () =&gt; await generator.GenerateForControllersAsync(controllers))
              .GetAwaiter().GetResult();
          var x= document.ToJson();
  </code></pre>
  
  <p>Thanks</p>