How to build applications using .NET? Building applications with .NET can be achieved through the following steps: 1) Understand the basics of .NET, including C# language and cross-platform development support; 2) Learn core concepts such as components and working of the .NET ecosystem; 3) Master basic and advanced usage, from simple console applications to complex Web APIs and database operations; 4) Be familiar with common errors and debugging techniques, such as configuration and database connection issues; 5) Application performance optimization and best practices, such as asynchronous programming and caching.

introduction

When we talk about modern software development, the .NET ecosystem is undoubtedly the best among them. As an all-round development platform, .NET provides comprehensive support from desktop applications to mobile applications to cloud services. Today, I will take you into a deep dive into how to build applications with .NET, from basic to advanced, and gradually reveal the charm of this powerful platform. After reading this article, you will learn how to use the .NET ecosystem to build efficient and scalable applications, and learn some of the experience and skills I have personally accumulated during the development process.

Review of basic knowledge

.NET is a software framework developed by Microsoft that helps developers create and run applications. It includes a variety of programming languages ??such as C#, VB.NET, and F#, of which C# is the most commonly used. .NET provides rich class libraries and APIs, supporting cross-platform development, allowing developers to write code at once and run on multiple operating systems.

C# is a modern, object-oriented programming language that combines the power of C and C while simplifying syntax. It supports garbage collection, type safety and exception handling, allowing developers to focus more on business logic than underlying details.

Core concept or function analysis

Definition and role of .NET ecosystem

The .NET ecosystem is a comprehensive development platform that includes multiple components such as .NET Framework, .NET Core (now renamed .NET 5), ASP.NET, Xamarin, etc. Its function is to provide a unified development environment that supports multiple application types, from traditional desktop applications to modern cloud-native applications.

// C# example: Simple console application using System;
<p>namespace HelloWorld
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hello, .NET World!");
}
}
}</p>

This simple example shows how to write a console application using C#. Through the Console.WriteLine method, we can easily output information to the console.

How it works

The .NET ecosystem works based on the Common Language Runtime (CLR) and the Common Language Infrastructure (CLI). CLR is responsible for managing memory, handling exceptions, and executing code, while the CLI provides a set of standards that enable code written in different languages ??to run seamlessly on the .NET platform.

During development, the .NET compiler compiles C# code into an intermediate language (IL), and CLR then converts IL into machine code at runtime. This approach makes .NET applications cross-platform capability because ILs can be executed in CLRs on different operating systems.

Example of usage

Basic usage

Let's look at a more complex example of creating a simple Web API using ASP.NET Core.

// ASP.NET Core Web API example using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
<p>namespace MyWebApi
{
public class Startup
{
public void ConfigureServices(IServiceCollection services)
{
services.AddControllers();
}</p><pre class='brush:php;toolbar:false;'> public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseRouting();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        CreateHostBuilder(args).Build().Run();
    }

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseStartup<Startup>();
            });
}

}

This example shows how to set up an ASP.NET Core Web API project, including configuration services and middleware. With AddControllers method, we can easily add controller support, while UseEndpoints defines the routing of the API.

Advanced Usage

Now, let's see how to use Entity Framework Core for database operations, a more advanced usage.

// Example using Microsoft.EntityFrameworkCore;
using System.Collections.Generic;
using System.Linq;
<p>namespace MyWebApi.Models
{
public class MyDbContext : DbContext
{
public DbSet<User> Users { get; set; }</p><pre class='brush:php;toolbar:false;'> protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer("Server=myServerAddress;Database=myDataBase;User Id=myUsername;Password=myPassword;");
    }
}

public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class UserService
{
    private readonly MyDbContext _context;

    public UserService(MyDbContext context)
    {
        _context = context;
    }

    public List<User> GetAllUsers()
    {
        return _context.Users.ToList();
    }

    public void AddUser(User user)
    {
        _context.Users.Add(user);
        _context.SaveChanges();
    }
}

}

In this example, we use Entity Framework Core to connect to the SQL Server database and define a User model and a UserService class to manage user data. With DbContext and DbSet , we can easily perform CRUD operations.

Common Errors and Debugging Tips

Common errors when developing with .NET include configuration issues, dependency injection errors, and database connection issues. Here are some debugging tips:

• Configuration issues : Make sure your appsettings.json file is configured correctly, especially connection strings and environment variables.
• Dependency injection error : Check the ConfigureServices method in your Startup.cs file to make sure all services are registered correctly.
• Database connection problem : Use Entity Framework Core's migration feature to manage database schemas to ensure that the database connection string is correct.

Performance optimization and best practices

Performance optimization and best practices are crucial in .NET development. Here are some suggestions:

• Asynchronous programming : Use the async/await keyword to write asynchronous code to improve application responsiveness and throughput.

// Asynchronous programming example public async Task <List<User> > GetAllUsersAsync()
{
    return await _context.Users.ToListAsync();
}

• Caching : Use in-memory cache or distributed cache to reduce the number of database queries and improve application performance.

// Cache example using Microsoft.Extensions.Caching.Memory;
<p>public class UserService
{
private readonly IMemoryCache _cache;
private readonly MyDbContext _context;</p><pre class='brush:php;toolbar:false;'> public UserService(IMemoryCache cache, MyDbContext context)
{
    _cache = cache;
    _context = context;
}

public async Task<List<User>> GetAllUsersAsync()
{
    string cacheKey = "allUsers";
    if (!_cache.TryGetValue(cacheKey, out List<User> users))
    {
        users = await _context.Users.ToListAsync();
        var cacheEntryOptions = new MemoryCacheEntryOptions()
            .SetSlidingExpiration(TimeSpan.FromMinutes(5));

        _cache.Set(cacheKey, users, cacheEntryOptions);
    }
    return users;
}

}

• Code readability : Follow the naming convention, use meaningful variable names and method names, write clear comments, and improve the maintainability of the code.

• Unit Testing : Write unit tests to ensure the correctness and reliability of the code, especially when refactoring.

// Unit test example using Xunit;
<p>public class UserServiceTests
{
[Fact]
public async Task GetAllUsersAsync_ReturnsAllUsers()
{
// Arrange
var context = new MyDbContext();
var service = new UserService(context);</p><pre class='brush:php;toolbar:false;'> // Act
    var users = await service.GetAllUsersAsync();

    // Assert
    Assert.NotNull(users);
    Assert.NotEmpty(users);
}

}

During my development career, I have found the flexibility and power of the .NET ecosystem to enable me to quickly build and deploy applications of all types. From simple console applications to complex microservice architectures, .NET provides a wealth of tools and libraries to support my development needs. I hope this article can help you better understand and utilize the .NET ecosystem and build efficient and scalable applications.

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