Web api Controller having constructors with parameters as Generic Service Interface

Question

In my Web api project I am having a controller DocumentViewerV1Controller which has a code as:

      /// <summary>
    /// 
    /// </summary>
    /// <param name="documentViewerService"></param>
    public DocumentViewerV1Controller(IDocumentViewerService<HtmlViewInformation> documentViewerService)
    {
        _documentViewerHtmlService = documentViewerService;
    }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="documentViewerService"></param>
    public DocumentViewerV1Controller(IDocumentViewerService<PageImage> documentViewerService)
    {
        _documentViewerImageService = documentViewerService;
    }/// <summary>
    /// Rendering Document as Html
    /// </summary>
    /// <returns></returns>
    [HttpGet]
    [Route(WebApiConfig.RootApiUri + "/v1/viewashtml/{docid}")]
    public string ViewAsHtml(string docId)
    {
        var documentInfo = new DocumentInfo { DocumentName = HostingEnvironment.MapPath("~/Uploads/") + docId };
        var response = _documentViewerHtmlService.RenderDocument(documentInfo, DocumentRenderType.Html);
        return GenerateResponse(response);
    }

When I run my service, make a call and debug the constructor initialization, It doesn't goes through the initialization which makes _documentViewerHtmlService as null, eventually fails returning Null reference Exception.

Is it possible to have service Interface as IDocumentViewerService?

@Karthik M R This is -> public DocumentViewerV1Controller(IDocumentViewerService<HtmlViewInformation> documentViewerService) { _documentViewerHtmlService = documentViewerService; } — Pushpendra
– Pushpendra, Commented Apr 20, 2016 at 14:04
But your class name is DocumentViewerController right?How will the function DocumentViewerV1Controller gets called? — Karthik M R
– Karthik M R, Commented Apr 20, 2016 at 14:05

Aydin · Accepted Answer · 2016-04-20 14:08:36Z

1

Yes, but you'll need to remove one of the constructors or tell it which one to use.

container.RegisterType<IViewerInformation, HtmlViewerInformation>();
container.RegisterType<IDocumentViewerService<IViewerInformation>, DocumentViewerServce<IViewerInformation>>();

You may / may not also need to initialize some of the constructors which you can do by

container.RegisterType<IDocumentViewerService<IViewerInformation>, DocumentViewerServce<IViewerInformation>>(
    new InjectionConstructor(...));

answered Apr 20, 2016 at 14:08

Aydin

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4 Comments

Pushpendra Over a year ago

I tried this way : container.RegisterType<IDocumentViewerService<HtmlViewInformation>, DocumentViewerService<HtmlViewInformation>>(new InjectionConstructor(typeof(IViewerHtmlRepository))); container.RegisterType<IDocumentViewerService<PageImage>, DocumentViewerService<PageImage>>(new InjectionConstructor(typeof(IViewerImageRepository))); Is there anything I am doing wrong?

Aydin Over a year ago

You can only run the constructor once, which constructor do you want to use?

Pushpendra Over a year ago

I want to use both the constructors depending on the calls which I will be making.

Aydin Over a year ago

You can't do that, if you need both, supply them both in the same constructor.

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