How do I configure .NET core DI in a file

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Using .NET Core 6 dependency injection I have code in Program.cs looking like this

C#

...

IConfigurationBuilder configuration = new ConfigurationBuilder();
configuration.SetBasePath(Directory.GetCurrentDirectory());
var host = Host.CreateDefaultBuilder()
    .ConfigureServices((context, services) =>
    {
        services.AddSingleton<IFileLogging, FileLogging>();
    }).Build();
logging = ActivatorUtilities.GetServiceOrCreateInstance<IFileLogging>(host.Services);
logging.Debug(log4net, "Starting up...");
Console.ReadLine();

It works nicely. I get a reference to a singleton for the interface IFileLogging.

Now I'm wondering if there is a way to perform the configuration in an external json file, i.e. moving the line

C#

services.AddSingleton<IFileLogging, FileLogging>();

to a separate json file, i.e. something along the lines

JSON

{
  "components": [
    {
      "type": "DITest.Default_DI_Namespace.FileLogging, DITest",
      "services": [
        {
          "type": "DITest.Default_DI_Namespace.IFileLogging, DITest"
        }
      ],
      "instanceScope": "single-instance",
      "injectProperties": true
    }
  ]
}

I assume that I need to configure my services to get the information from file, but I don't know how.

If anyone has an idea I would be most grateful.

King regards
Magnus

What I have tried:

I've Googled quite a lot, but mostly found how to read settings from appsettings.json for getting data.
Example[^]

Posted 17-Jan-22 0:10am

Magnus Sydoff

Updated 17-Jan-22 7:12am

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2 solutions

Solution 1

Check this: Article is doing the same thing

.NET Core Dependency Injection with Configuration – csharp.christiannagel.com[^]

Posted 17-Jan-22 1:20am

_Asif_

Comments

Magnus Sydoff 17-Jan-22 13:05pm

Hi _Asif,

Yes, I looked at that article, but if I'm not misreading it, it just gives me a value in return, not wiring up my services.

I have ended up writing my own implementation that reads from a json file and then looks at the defined interfaces and classes and wires it up.

Thanks!

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Magnus Sydoff · Accepted Answer · 2022-01-17T07:12:00

I finally gave up Googling this issue and took a deep look on how the automatic variant of injecting services was made.

I used this NuGet package, AutoRegisterDI[^]
as a starting point and ended up something looking like the code below (some of my own types are not shown for brevity, but I hope the general idea comes across)

C#

Assembly assemblyForInterface = Assembly.LoadFrom(Path.Combine(folderToLoadModulesFrom, config.InterfaceDefinition.FileName));
Assembly assemblyForImplementation = Assembly.LoadFrom(Path.Combine(folderToLoadModulesFrom, config.ConcreteClassImplementation.FileName));

var exportedTypes = assemblyForImplementation.GetExportedTypes();
var implementationClass = exportedTypes.FirstOrDefault(t => t.Name == config.ConcreteClassImplementation.DefinedType && t.IsClass && !t.IsAbstract && !t.IsNested);
if (implementationClass == null)
{
    Console.WriteLine($"* Unable to find implementation {config.ConcreteClassImplementation.DefinedType} in file {config.ConcreteClassImplementation.FileName}. This config will not be used.");
    return;
}
var interfaceForImplementation = assemblyForInterface.GetExportedTypes().FirstOrDefault(t => t.Name == config.InterfaceDefinition.DefinedType && t.IsPublic && !t.IsNested);
if (interfaceForImplementation == null)
{
    Console.WriteLine($"* Unable to find interface {config.InterfaceDefinition.DefinedType} in file {config.InterfaceDefinition.FileName}. This config will not be used.");
    return;
}

if (!(ServiceLifetime.TryParse(typeof(ServiceLifetime), config.ServiceLifetime, out object lifetimeObject)) || (lifetimeObject is null))
{
    Console.WriteLine($"* Unable to parse {nameof(ServiceLifetime)} from value {config.ServiceLifetime}. This config will not be used.");
    return;
}
ServiceLifetime lifetime = (ServiceLifetime)lifetimeObject;

services.Add(new ServiceDescriptor(interfaceForImplementation, implementationClass, lifetime));