In an Asp.Net MVC Core (early versions, versions 1.0 or 1.1), dependency injection bindings are configured as follow in the Startup.cs class :
public class Startup
{
public void ConfigureServices(IServiceCollection services)
{
services.AddScoped<IMyService, MyService>();
// ...
}
}
In my applications, I usually have a base Startup class, where generic bindings are defined as a sequence of these lines :
public abstract class BaseStartup
{
public virtual void ConfigureServices(IServiceCollection services)
{
services.AddScoped<IMyService1, MyService1>();
services.AddScoped<IMyService2, MyService2>();
}
}
Then in my application, I inherit the startup class, and inject other services as well :
public class Startup : BaseStartup
{
public override void ConfigureServices(IServiceCollection services)
{
base.ConfigureServices(services);
services.AddScoped<IMyService3, MyService3>();
services.AddScoped<IMyService4, MyService4>();
}
}
I now wonder : how can I kind of 'override' a previous binding ? I would like, for instance, to either remove, or modify a binding defined in the base class, like :
services.Remove<IMyService1>(); // Doesn't exist
services.AddScoped<IMyService1, MyBetterService1>();
Or simply update the binding :
services.AddScoped<IMyService1, MyBetterService1>(replacePreviousBinding: true); // Doesn't exist either !
Is there a way to do that ? Or maybe simply declaring a new binding with the same interface as a previously defined binding will override that binding ?
You can use normal collection API to remove your services:
services.AddScoped<IService>();
var serviceDescriptor = services.FirstOrDefault(descriptor => descriptor.ServiceType == typeof(IService));
services.Remove(serviceDescriptor);
Also you can create extension methods to achieve the same:
public static class ServiceCollectionExtensions
{
public static IServiceCollection Remove<T>(this IServiceCollection services)
{
if (services.IsReadOnly)
{
throw new ReadOnlyException($"{nameof(services)} is read only");
}
var serviceDescriptor = services.FirstOrDefault(descriptor => descriptor.ServiceType == typeof(T));
if (serviceDescriptor != null) services.Remove(serviceDescriptor);
return services;
}
}