DBContext Middleware

Question

I am having trouble understanding the Program.cs class. I can't find any articles on how everything fits together. For example, why do we enclose in angle brackets the IUser Interface and the class that implements it UserManager likeso <IUser, UserManager>? Where does the builder class fit into all of this? And I also don't understand the options => statement. I know this question is loaded but I am having trouble understanding so that I can apply this to something I can build on my own or maybe someone has an example of where this same syntax is used in injecting a service into a container that is used as Middleware. I don't like using code that I don't fully understand. How does this code ultimately result in exploiting the concept of Dependency Injection.

builder.Services.AddDbContext<DatabaseContext>
(options =>
options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));

builder.Services.AddTransient<IUser, UserManager>();

Answer 1

You should learn c#. The net 6 makes heavy use if the following c# features

Interfaces
generics
lambda (closure) functions
Expression trees (used with binding)

Then there are several design patterns you should know very well

Interface design pattern
Dynamic dependency injection pattern (DI)
The builder pattern

Once you learn the above it will be simple to read. <> are used with generic interfaces. The builder pattern and DI is key to understanding the program.cs file.

Answer 2

You should learn c#. The net 6 makes heavy use if the following c# features

Interfaces
generics
lambda (closure) functions
Expression trees (used with binding)

Then there are several design patterns you should know very well

Interface design pattern
Dynamic dependency injection pattern (DI)
The builder pattern

Once you learn the above it will be simple to read. <> are used with generic interfaces. The builder pattern and DI is key to understanding the program.cs file.

For example

// register a dbcontext for DI using a generic method to define the actual type  
// then pass a lambda to initial the DatabaseContext parameters  
builder.Services.AddDbContext<DatabaseContext>  
(options =>  
options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));  
  
// register a concrete  type of IUser to be available to be injected  
// transient says it created on every request  
// AddTransient is a generic method requiring two type definitions   
// it’s actually overload so there are several signatures   
builder.Services.AddTransient<IUser, UserManager>();  

Answer 3

Hi @Ronald Rex ,

You can refer the following tutorials to learn how the use Dependency injection in asp.net core:

Dependency injection in ASP.NET Core.

And refer to the Tutorial: Get started with EF Core in an ASP.NET MVC web app or Part 5, work with a database in an ASP.NET Core MVC app to learn how to use the EF core in asp.net core:

Then, to use the UserManager and Asp.net core Identity, you can refer to the following links:

Introduction to Identity on ASP.NET Core

Scaffold Identity in ASP.NET Core projects

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Best regards
Dillion