PosInformatique.AspNet.WebForms.DependencyInjection

PosInformatique.AspNet.WebForms.DependencyInjection is a library to add the IoC container support of Microsoft.Extensions.DependencyInjection for ASP .NET Web Forms

Installing from NuGet

The PosInformatique.AspNet.WebForms.DependencyInjection is available directly on the NuGet official website. To download and install the library to your Visual Studio project using the following NuGet command line

Install-Package PosInformatique.AspNet.WebForms.DependencyInjection

Setting up

After adding the PosInformatique.AspNet.WebForms.DependencyInjection package on your ASP .NET WebForms project call the AddServiceCollection the following lines in the Application_Start of your HttpApplication class in the Global.asax.cs code behind:

public class Global : HttpApplication
{
    protected void Application_Start(Object sender, EventArgs e)
    {
        ServicesConfig.RegisterServices(this.AddServiceCollection());

        // Code that runs on application startup
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);
    }
}

In the App_Start folder add a new static class called ServicesConfig which allows to register the services using the Microsoft.Extensions.DependencyInjection.ServiceCollection:

namespace PosInformatique.AspNet.WebForms.DependencyInjection.IntegrationTests
{
    using System;
    using System.Collections.Generic;
    using System.Collections.ObjectModel;
    using System.Linq;
    using Microsoft.Extensions.DependencyInjection;

    public static class ServicesConfig
    {
        public static void RegisterServices(IServiceCollection serviceCollection)
        {
            serviceCollection.AddSingleton<IDogRepository, DogRepository>();
            serviceCollection.AddTransient<IDogManager, DogManager>();
        }
    }
}

You can register services with a Transient or Singleton scope. Unlike to ASP .NET Core, PosInformatique.AspNet.WebForms.DependencyInjection does not support Scoped scope services which exists during the HTTP request lifetime.

Setting up using an existing IServiceProvider/IServiceCollection

If in your ASP .NET application you host the ASP .NET Core infrastructure (using the PosInformatique.AspNetCore.Server.AspNet library for example), you can reuse the IServiceProvider and IServiceCollection internally builded by the ASP .NET Core infrastructure to share the same services (and same singleton instances !) between your ASP .NET application and ASP .NET Core hosted application.

The following example, show how to reuse the internal IServiceProvider and IServiceCollection of ASP .NET Core application hosted in ASP .NET using the PosInformatique.AspNetCore.Server.AspNet library:

public class Global : System.Web.HttpApplication
{
    protected void Application_Start(object sender, EventArgs e)
    {
        var host = WebHost.CreateDefaultBuilder()
            .UseAspNet(options =>
            {
                options.Routes.Add("api");
                options.Routes.Add("swagger");
            })
            .ConfigureServices(services =>
            {
                // Add the default ASP .NET non-core services
                // in the IServiceCollection of ASP .NET core.
                services.AddDefaultAspNetServices(this);
            })
            .UseStartup<Startup>()
            .Start();

        // Reuse the built IServiceProvider of ASP .NET Core WebHost inside
        // the ASP .NET non-core infrastructure to use IoC feature.
        this.UseServiceProvider(host);
    }
}

The AddDefaultAspNetServices() method allows to add ASP .NET non-core infrastructure service like the HttpRequest or HttpContext into the IServiceCollection which will be available in the IServiceProvider built by the ASP .NET core infrastructure.

The UseServiceProvider() method allows to setup the ASP .NET non-core infrastructure to use the implementation of IServiceProvider which is builted by the IWebHost of the ASP .NET Core infrastructure started.

With this approach the ASP .NET non-core and Core components will share the same service. For example, if you register a IDogManager service as singleton in the services of ASP .NET Core, the IDogManager service instance will be available and the same instance:

• In the constructors of the ASP .NET Web Forms pages, user controls,...
• In the constructors of the ASP .NET Core controllers
• And so on...

Add the support of [ActivatorUtilitiesConstructor] attribute

By default, the Microsoft.Extensions.DependencyInjection dependency injection container will use any constructor which match the parameters of the control, or service to instantiate. In the version 2.1 of Microsoft.Extensions.DependencyInjection library, Microsoft has introduced a new ActivatorUtilitiesConstructorAttribute attribute which allows to force the IServiceProvider of the Microsoft.Extensions.DependencyInjection library to call explicitely the constructor decorated.

The version 1.2.0 of the PosInformatique.AspNet.WebForms.DependencyInjection library add the support of the ActivatorUtilitiesConstructorAttribute attribute even technically this attribute is not added by the ASP .NET Compiler on the generated ASPX and ASCX views.

For example, imagine that you have the following user control:

public partial class UserControlWithDependency : System.Web.UI.UserControl
{
    private readonly IDogManager dogManager;

    [ActivatorUtilitiesConstructor]   // Will be call by the IServiceProvider of the Microsoft.Extensions.DependencyInjection library.
    public UserControlWithDependency(IDogManager dogManager)
    {
        this.dogManager = dogManager;
    }

    public UserControlWithDependency()
    {
    }
}

When the application is loaded the ASP .NET Compiler generate the following code which will not add the ActivatorUtilitiesConstructorAttribute attribute on the constructors associated:

public class usercontrolwithdependency_ascx : UserControlWithDependency
{
	...

	[DebuggerNonUserCode]
	public usercontrolwithdependency_ascx()
	{
		__Init();
	}

	[DebuggerNonUserCode]
	public usercontrolwithdependency_ascx(IDogManager dogManager)
		: base(dogManager)
	{
		__Init();
	}

    ...
}

The previous generated code can not be used correctly by the Microsoft.Extensions.DependencyInjection library to call the right constructor based on the ActivatorUtilitiesConstructorAttribute.

In the version 1.2.0, the PosInformatique.AspNet.WebForms.DependencyInjection add the full support of the ActivatorUtilitiesConstructorAttribute by virtually add the attribute by reflection in the class generated by the ASP .NET Compiler.

Issue in the ASPX/ASCX designer

When changing the constructor of the user controls and control to inject dependencies using the HttpRuntime.WebObjectActivator, the following message can appear when adding these controls to a page or other user controls:

Element 'xxxxx' is not a known element. This can occur if there is a compilation error in the Web site, or the web.config file is missing.

In this case, lot of fakes errors/warnings can be raised by Visual Studio (but the application can compile successfully).

Also, the IntelliSense for the ASPX code to edit the properties of the added controls does not work...

This is a known issue of Visual Studio and Microsoft seam to take Under Consideration...

There is workaround, which is provided with the PosInformatique.AspNet.WebForms.DependencyInjection package by adding a constructor without parameter in the control:

public partial class UserControlWithDependency : System.Web.UI.UserControl
{
    private readonly IDogManager dogManager;

    [ActivatorUtilitiesConstructor]   // It is import to set this attribute to be sure this constructor will be called by the Microsoft.Extensions.DependencyInjection.
    public UserControlWithDependency(IDogManager dogManager)
    {
        this.dogManager = dogManager;
    }

    // Avoid the errors and the warnings in the Visual Studio ASPX code designer
    public UserControlWithDependency()
    {
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        this.doggoList.DataSource = this.dogManager.GetDogs();
        this.doggoList.DataBind();
    }
}

Remarks: You have also to add the ActivatorUtilitiesConstructorAttribute on the constructor which requires the services registered in the Microsoft.Extensions.DependencyInjection container. Without this attribute, the constructor without parameter can be used during the execution of the application with the default behavior of the Microsoft.Extensions.DependencyInjection.

Contributions

Do not hesitate to clone my code and submit some changes... It is a open source project, so everyone is welcome to improve this library... By the way, I am french... So maybe you will remarks that my english is not really fluent... So do not hesitate to fix my resources strings or my documentation... Merci !

Thanks

I want to thank the DiliTrust company to test and gave me their feedback of this library for their ASP .NET WebForms applications.