我正在尝试使用 SqlDependency 类监视数据库表的更改。虽然我一定是错过了什么。我遵循了我在网上看到的所有示例，并查看了该站点上的所有问题。我只是不明白我错过了什么。以下是我在数据库上运行以启用服务代理并创建队列和服务的初始命令。
CREATE QUEUE ScheduleChangeQueue
GO
CREATE SERVICE ScheduleChangeService ON QUEUE ScheduleChangeQueue ([http://schemas.microsoft.com/SQL/Notifications/PostQueryNotification])
GO
ALTER DATABASE [database] SET ENABLE_BROKER
在 C# 方面，我创建了一个类，该类具有一个静态 Setup 方法，该方法被调用以启动该过程。这是代码：
public class SqlDependencyManager
{
private static bool DoesUserHavePermission()
{
var success = false;
try
{
Program.Log.Info("Retrieving SqlPermission to establish dependency...");
var clientPermission = new SqlClientPermission(System.Security.Permissions.PermissionState.Unrestricted);
// this will throw an error if the user does not have the permissions
clientPermission.Demand();
success = true;
Program.Log.Info("SqlPermission established. Continue setting up dependency.");
}
catch (Exception ex)
{
Program.Log.Error(ex, "SqlPermission not able to be established.");
}
return success;
}
public static void Setup()
{
if (!DoesUserHavePermission())
{
return;
}
var connectionString = ConfigurationManager.ConnectionStrings["ShowMakerPro"].ConnectionString;
// You must stop the dependency before starting a new one.
// You must start the dependency when creating a new one.
SqlDependency.Stop(connectionString);
SqlDependency.Start(connectionString);
using (var cn = new SqlConnection(connectionString))
{
using (var cmd = cn.CreateCommand())
{
cmd.CommandType = CommandType.Text;
//cmd.CommandText = "SELECT MAX(LastChangeTime) FROM Schedule WHERE ChannelID IN ( SELECT ID FROM Channels WHERE Type = 1 ) AND StartTime BETWEEN (GETDATE() - 7) AND (GETDATE() + 30)";
cmd.CommandText = "SELECT LastChangeTime FROM dbo.Schedule";
cmd.Notification = null;
// Creates a new dependency for the SqlCommand. Then creates attaches handler for the notification of data changes
new SqlDependency(cmd).OnChange += SqlDependency_OnChange;
cn.Open();
cmd.ExecuteReader();
}
}
Program.Log.Info("SQL Dependency set. Now monitoring schedule table for changes.");
}
private static void SqlDependency_OnChange(object sender, SqlNotificationEventArgs e)
{
if (e.Type == SqlNotificationType.Change)
{
// this will remove the event handler since the dependency is only for a single notification
((SqlDependency)sender).OnChange -= SqlDependency_OnChange;
ScheduleOutputterService.BuildSchedules();
Program.Log.Info("SQL Dependency triggered schedule rebuild. Resetting SqlDependency to monitor for changes.");
Setup();
}
}
}
我看到代码设置正常，并且 OnChange 方法为订阅触发了一次，但之后我再也没有看到它触发过。我手动进入数据库并更改 LastChangeTime 字段，希望它会强制触发事件，但没有任何反应。
有人可以说明我在哪里搞砸了吗？我看到有人在网上说这在 Windows 窗体中可以正常工作，但他们在服务中也遇到了一些问题。