The instance of entity type 'Item' cannot be tracked because another instance with the same key value for {'Id'} is already being tracked

//将

services.AddEntityFrameworkSqlServer().AddDbContext<OcelotConfigDbContext>(ServiceLifetime.Singleton);

//更改为

services.AddDbContext<OcelotConfigDbContext>(c => c.UseSqlServer(Guid.NewGuid().ToString())
            .UseQueryTrackingBehavior(QueryTrackingBehavior.NoTracking));

 

即可