Asp.net core Webapi 如何执行定时任务？ - ToB企服应用市场:ToB评测及商务社交产业平台

创建一个 asp.net core webapi 项目

从 Nuget 安装以下包

Microsoft.AspNetCore.Identity.EntityFrameworkCore
Microsoft.EntityFrameworkCore.Relational
Microsoft.EntityFrameworkCore.SqlServer
Microsoft.EntityFrameworkCore.Tools

打开 appsettings.json 并添加数据库连接字符串，如：

{
"Logging": {
"LogLevel": {
"Default": "Information",
"Microsoft.AspNetCore": "Warning"
}
},
"AllowedHosts": "*",
"ConnectionStrings": {
"Default": "Server=(localdb)\\mssqllocaldb;Database=IdentityTestDB;Trusted_Connection=True;MultipleActiveResultSets=true"
}
}

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添加一个继承于 IdentityUser 的 User 类

using Microsoft.AspNetCore.Identity;
public class User: IdentityUser<long>
{
public DateTime CreationTime { get; set; }
public string? NickName { get; set; }
}

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添加一个继承于 IdentityRole 的 Role 类

using Microsoft.AspNetCore.Identity;
public class Role: IdentityRole<long>
{
}

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创建数据库上下文

using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;
public class TestDbContext: IdentityDbContext<User, Role, long>
{
public TestDbContext(DbContextOptions<TestDbContext> options):base(options)
{
}
protected override void OnModelCreating(ModelBuilder builder)
{
base.OnModelCreating(builder);
builder.ApplyConfigurationsFromAssembly(this.GetType().Assembly);
}
}

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创建一个 ExplortStatisticBgService 类并继承 BackgroundService，这是托管服务类

using Microsoft.EntityFrameworkCore;
using System.Text;
public class ExplortStatisticBgService : BackgroundService
{
private readonly TestDbContext ctx;
private readonly ILogger<ExplortStatisticBgService> logger;
private readonly IServiceScope serviceScope;
/// <summary>
/// 在构造方法注入IServiceScopeFactory服务，
/// 用来创建IServiceScope对象，
/// 这样就可以通过IServiceScope来创建短生命周期的服务了
/// </summary>
/// <param name="scopeFactory"></param>
public ExplortStatisticBgService(IServiceScopeFactory scopeFactory)
{
this.serviceScope = scopeFactory.CreateScope();
var sp = serviceScope.ServiceProvider;
this.ctx = sp.GetRequiredService<TestDbContext>();
this.logger = sp.GetRequiredService<ILogger<ExplortStatisticBgService>>();
}
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
// 用 while 循环实现服务常驻
while (!stoppingToken.IsCancellationRequested)
{
// 用 try...catch 捕捉异常记录错误信息并避免方法退出
try
{
// 这里实现每隔5秒从数据库中导出数据
// 更复杂的配置可以用第三方开源的框架
await DoExecuteAsync();
await Task.Delay(5000);
}
catch (Exception ex)
{
logger.LogError(ex, "获取用户统计数据失败");
await Task.Delay(1000);
}
}
}
private async Task DoExecuteAsync()
{
var items = ctx.Users.AsNoTracking().GroupBy(u => u.CreationTime.Date)
.Select(e => new
{
Date = e.Key,
Count = e.Count()
});
StringBuilder sb = new StringBuilder(1024);
sb.AppendLine($"Date: {DateTime.Now}");
foreach (var item in items)
{
sb.Append(item.Date).AppendLine($": {item.Count}");
}
await File.WriteAllTextAsync("d:/1.txt", sb.ToString());
logger.LogInformation($"导出完成");
}
/// <summary>
/// IServiceScope 需要释放
/// 所以重写 Dispose 方法
/// </summary>
public override void Dispose()
{
base.Dispose();
serviceScope.Dispose();
}
}

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打开 Program.cs，注入托管服务等，看代码的注释

using Microsoft.AspNetCore.Identity;
using Microsoft.EntityFrameworkCore;
var builder = WebApplication.CreateBuilder(args);
// Add services to the container.
builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
IServiceCollection services = builder.Services;
// 注册托管服务
services.AddHostedService<ExplortStatisticBgService>();
// 注入数据库上下文
services.AddDbContext<TestDbContext>(options => {
string connStr = builder.Configuration.GetConnectionString("Default")!;
options.UseSqlServer(connStr);
});
// 数据保护服务注入
// ----数据保护提供了一个简单、基于非对称加密改进的加密API用于确保Web应用敏感数据的安全存储
// ----不需要开发人员自行生成密钥，它会根据当前应用的运行环境，生成该应用独有的一个私钥
services.AddDataProtection();
// 注入 Identity 框架的一些重要的基础配置
// 如果没有这个，下面的注入 UserManager 等服务会有问题，程序无法编译
services.AddIdentityCore<User>(options =>
{
options.Password.RequireDigit = false;
options.Password.RequireLowercase = false;
options.Password.RequireNonAlphanumeric = false;
options.Password.RequireUppercase = false;
options.Password.RequiredLength = 6;
options.Tokens.PasswordResetTokenProvider = TokenOptions.DefaultEmailProvider;
options.Tokens.EmailConfirmationTokenProvider = TokenOptions.DefaultEmailProvider;
});
// 注入 UserManager、RoleManager 等Identity 框架服务
var idBuilder = new IdentityBuilder(typeof(User), typeof(Role), services);
idBuilder.AddEntityFrameworkStores<TestDbContext>()
.AddDefaultTokenProviders()
.AddRoleManager<RoleManager<Role>>()
.AddUserManager<UserManager<User>>();
var app = builder.Build();
// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
app.UseSwagger();
app.UseSwaggerUI();
}
app.UseHttpsRedirection();
app.UseAuthorization();
app.MapControllers();
app.Run();
``

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Ctrl+F5 运行项目，不做任何操作，托管程序会自动导出数据