Dependency Injection

What is it?

Dependency Injection in ASP.NET development, is a technique used for creating instances of needed dependencies in different parts of an application. Each dependency is a Service, with shared functionality that can be reused.

---

Injecting services

To use a Service, it needs to be injected. Let’s inject a Service in the Middleware Pipeline:

// Set WebApplicationBuilder  
var builder = WebApplication.CreateBuilder(args);  
  
// Register services  
builder.Services.AddSingleton<IService, MyService>();  
  
// Set to building  
var myApp = builder.Build();  
  
void ConfigureMiddleware(IApplicationBuilder app)  
{  
    //  From the HTTP context, defines the first middleware and invokes the second  
    app.Run(async context =>  
    {  
        await context.Response.WriteAsync($"Hello from {context.Request.Path} \n");  
  
        // Injects service  
        var myService = app.ApplicationServices.GetRequiredService<IService>();  
        await context.Response.WriteAsync(myService.Method());  
    });  
}  
  
// Applies configuration  
ConfigureMiddleware(myApp);  
  
// Runs the WebApp.  
myApp.Run();