1、通过配置实体类的方式

1）配置实体类

public class Settings
{
    public string From { get; set; }
    public string SmtpServer { get; set; }
    public int Port { get; set; }
    public string Username { get; set; }
    public string Password { get; set; }
}

2）appsettings.json配置文件内容

"settings": {
    "From": "url@gmail.com",
    "SmtpServer": "smtp.gmail.com",
    "Port": 465,
    "Username": "url@gmail.com",
    "Password": "123456"
  }

3）实现代码

using Microsoft.OpenApi.Models;
using NLog.Web;

var builder = WebApplication.CreateBuilder(args);
// Add services to the container.
builder.Logging.ClearProviders();
builder.Host.UseNLog();
//获取 appsettings.json 中配置
var settings = builder.Configuration.GetSection("Settings").Get<Settings>();
var smtpServer = settings.SmtpServer;
builder.Services.AddControllers();

builder.Services.AddEndpointsApiExplorer();
var app = builder.Build();
ServiceLocator.Instance = app.Services;
//app.UseAuthentication();
//app.UseAuthorization();
app.UseDefaultFiles();
app.UseStaticFiles();
app.MapControllers();
app.Run();

2、通过Configuration属性来获取

1）appsettings.json配置内容

"settings": {
    "From": "url@gmail.com",
    "SmtpServer": "smtp.gmail.com",
    "Port": 465,
    "Username": "url@gmail.com",
    "Password": "123456"
}

2）实现代码

using Microsoft.OpenApi.Models;
using NLog.Web;

var builder = WebApplication.CreateBuilder(args);
// Add services to the container.
builder.Logging.ClearProviders();
builder.Host.UseNLog();
builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
var app = builder.Build();
ServiceLocator.Instance = app.Services;
//获取 appsettings.json 中配置
var config = app.Configuration;
var smtpServer = config["settings:SmtpServer"];
//app.UseAuthentication();
//app.UseAuthorization();
app.UseDefaultFiles();
app.UseStaticFiles();
app.MapControllers();