c# DbContext needs 20seconds

当我启动may控制台程序并初始化我的DbContext类时，我的程序每20秒等待一次。

没有dbContext类，一切都可以正常工作。有人知道为什么吗？

这里有些代码

public class CobraDataBaseContext : DbContext
{
    public DbSet<Material> Materials { get; set; }
    public DbSet<Site> Sites { get; set; }
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        // Ein Workplace hat eine Optinale Maschine ABER eine Maschine muss immer einem Workplace 
        // zugeordnet sein.
        modelBuilder.Entity<WorkPlace>().HasOptional(m => m.machine).WithRequired(wp => wp.workPlace);
        // one material has optinal specification
        modelBuilder.Entity<Material>().HasOptional(n => n.specification).WithMany();
    }
}

服务类

public Site getSite(字符串siteName({var site=dbContext.Sites.FirstOrDefault(s=>s.name.Equals(siteName((；

        foreach (var wp in site.workPlaces)
        {
            if (wp.numberOfWorkers != null)
            {
                double count = wp.numberOfWorkers.value.Value;
            }
        }

        return dbContext.Sites.FirstOrDefault(s => s.name.Equals(siteName));
    }