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Accessing ASP.NET Core DI Container From Static Factory Class

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闹比i
闹比i 2021-01-30 16:57

I\'ve created an ASP.NET Core MVC/WebApi site that has a RabbitMQ subscriber based off James Still\'s blog article Real-World PubSub Messaging with RabbitMQ.

In his arti

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  • 心在旅途
    心在旅途 (楼主)
    2021-01-30 17:35

    I know my answer is late, but I wanted to share how I did it.

    First of all: It's Antipattern to use ServiceLocator so try not to use it as you can. In my case I needed it to call MediatR inside of my DomainModel to implement the DomainEvents logic.

    However, I had to find a way to call a static class in my DomainModel to get an instance of some registered service from DI.

    So I've decided to use the HttpContext to access the IServiceProvider but I needed to access it from a static method without mention it in my domain model.

    Let's do it:

    1- I've created an interface to wrap the IServiceProvider

    public interface IServiceProviderProxy
{
    T GetService();
    IEnumerable GetServices();
    object GetService(Type type);
    IEnumerable GetServices(Type type);
}



    2- Then I've created a static class to be my ServiceLocator access point
    


    public static class ServiceLocator
{
    private static IServiceProviderProxy diProxy;

    public static IServiceProviderProxy ServiceProvider => diProxy ?? throw new Exception("You should Initialize the ServiceProvider before using it.");

    public static void Initialize(IServiceProviderProxy proxy)
    {
        diProxy = proxy;
    }
}

    


    3- I've created an implementation for the IServiceProviderProxy which use internally the IHttpContextAccessor
    


    public class HttpContextServiceProviderProxy : IServiceProviderProxy
{
    private readonly IHttpContextAccessor contextAccessor;

    public HttpContextServiceProviderProxy(IHttpContextAccessor contextAccessor)
    {
        this.contextAccessor = contextAccessor;
    }

    public T GetService()
    {
        return contextAccessor.HttpContext.RequestServices.GetService();
    }

    public IEnumerable GetServices()
    {
        return contextAccessor.HttpContext.RequestServices.GetServices();
    }

    public object GetService(Type type)
    {
        return contextAccessor.HttpContext.RequestServices.GetService(type);
    }

    public IEnumerable GetServices(Type type)
    {
        return contextAccessor.HttpContext.RequestServices.GetServices(type);
    }
}



    4- I should register the IServiceProviderProxy in the DI like this 
    


    public void ConfigureServices(IServiceCollection services)
{
    services.AddHttpContextAccessor();
    services.AddSingleton();
    .......
}

    


    5- Final step is to initialize the ServiceLocator with an instance of IServiceProviderProxy at the Application startup
    


    public void Configure(IApplicationBuilder app, IHostingEnvironment env,IServiceProvider sp)
{
    ServiceLocator.Initialize(sp.GetService());
}

    


    As a result now you can call the ServiceLocator in your DomainModel classes "Or and needed place" and resolve the dependencies that you need.
    


    public class FakeModel
{
    public FakeModel(Guid id, string value)
    {
        Id = id;
        Value = value;
    }

    public Guid Id { get; }
    public string Value { get; private set; }

    public async Task UpdateAsync(string value)
    {
        Value = value;
        var mediator = ServiceLocator.ServiceProvider.GetService();
        await mediator.Send(new FakeModelUpdated(this));
    }
}

    
    
    
             
    
                                                        
    
            
            
    
              
                
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