ABP.io 应用停止时，我们可以使用 HostApplicationLifetime 对象的 CancellationToken 来取消后台任务。具体实现方式如下：

1. 在 ApplicationModule.cs 的 ConfigureServices 方法中注入 HostApplicationLifetime 对象：

public override void ConfigureServices(ServiceConfigurationContext context) { ... context.Services.AddSingleton(); ... }

2. 创建一个实现 IHostApplicationLifetime 接口的包装器类 HostApplicationLifetimeWrapper，引入 Microsoft.Extensions.Hosting.Abstractions 命名空间：

using Microsoft.Extensions.Hosting;

public class HostApplicationLifetimeWrapper : IHostApplicationLifetime { private readonly IHostApplicationLifetime _lifetime;

public HostApplicationLifetimeWrapper(IHostApplicationLifetime lifetime)
{
    _lifetime = lifetime;
}

public CancellationToken ApplicationStarted => _lifetime.ApplicationStarted;

public CancellationToken ApplicationStopping => _lifetime.ApplicationStopping;

public CancellationToken ApplicationStopped => _lifetime.ApplicationStopped;

public void StopApplication() => _lifetime.StopApplication();

}

3. 在需要执行的后台任务类中注入 IHostApplicationLifetime 对象：

public class BackgroundService : ITransientDependency { private readonly IHostApplicationLifetime _applicationLifetime;

public BackgroundService(IHostApplicationLifetime applicationLifetime)
{
    _applicationLifetime = applicationLifetime;
}

public async Task DoWorkAsync(CancellationToken cancellationToken)
{
    while (!cancellationToken.IsCancellationRequested)
    {
        ...
    }

    // 应用停止时取消后台任务
    _applicationLifetime.ApplicationStopping.Register(() =>
    {
        ...
    });
}

}

4. 在 BackgroundService 中的 DoWorkAsync 方法中使用 CancellationToken 取消任务：

public async Task DoWorkAsync(CancellationToken cancellationToken) { while (!cancellationToken.IsCancellationRequested) { ... }

// 应用停止时取消后台任务
_applicationLifetime.ApplicationStopping.Register(() =>
{
    cancellationTokenSource.Cancel();
});

}

以上就是 ABP.io 应用停止时取消后台任务的解决方法。