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//案例：数据的定时导出
1  public class ExplortStatisticBgService : BackgroundService
2  {
3     private readonly TestDbContext ctx;
4     private readonly ILogger<ExplortStatisticBgService> logger;
5     private readonly IServiceScope serviceScope;
6     public ExplortStatisticBgService(IServiceScopeFactory scopeFactory)
7     {
8        this.serviceScope = scopeFactory.CreateScope();
9        var sp = serviceScope.ServiceProvider;
10       this.ctx = sp.GetRequiredService<TestDbContext>();
11       this.logger = sp.GetRequiredService<ILogger<ExplortStatisticBgService>>();
12    }
13    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
14    {
15       while (!stoppingToken.IsCancellationRequested)
16       {
17          try
18          {
19             await DoExecuteAsync();
20             await Task.Delay(5000);
21          }
22          catch (Exception ex)
23          {
24             logger.LogError(ex, "获取用户统计数据失败");
25             await Task.Delay(1000);
26          }
27       }
28    }
29    private async Task DoExecuteAsync()
30    {
31       var items = ctx.Users.GroupBy(u => u.CreationTime.Date)
32                   .Select(e => new { Date = e.Key, Count = e.Count() });
33       StringBuilder sb = new StringBuilder();
34       sb.AppendLine($"Date:{DateTime.Now}");
35       foreach (var item in items)
36       {
37          sb.Append(item.Date).AppendLine($":{item.Count}");
38       }
39       await File.WriteAllTextAsync("d:/1.txt", sb.ToString());
40       logger.LogInformation($"导出完成");
41    }
42    public override void Dispose()
43    {
44       base.Dispose();
45       serviceScope.Dispose();
46    }
47 }