[英]SqlDependency doesn't fire OnChange event when dataset is changed
我对使用SQL Server查询通知的概念是陌生的,需要花一些时间来解决这个问题。
我的目标是创建一个Windows服务应用程序,当对SQL Server表进行更改时会收到通知。 我遵循了该指南,这对帮助我入门很有帮助。
但是我无法获得预期的结果。 Windows服务应用程序中的OnStart()
方法如下所示:
protected override void OnStart(string[] args)
{
eventLog1.WriteEntry("Service Started");
serviceRun = false;
SqlClientPermission perm = new SqlClientPermission(System.Security.Permissions.PermissionState.Unrestricted);
try
{
perm.Demand();
eventLog1.WriteEntry("permission granted");
}
catch (System.Exception)
{
eventLog1.WriteEntry("permission denied");
}
try
{
connstr = "Data Source=THSSERVER-LOCAL;Initial Catalog=ET;User ID=mujtaba;Password=ths123";
connection = new SqlConnection(connstr);
SqlCommand command = new SqlCommand("select * from dbo.Customer_FileUploads", connection);
// Create a dependency and associate it with the SqlCommand.
SqlDependency dependency = new SqlDependency(command);
// Maintain the reference in a class member.
// Subscribe to the SqlDependency event.
dependency.OnChange += Dependency_OnChange;
SqlDependency.Start(connstr);
connection.Open();
// Execute the command.
using (SqlDataReader reader = command.ExecuteReader())
{
if (reader.HasRows)
{
while (reader.Read())
{
//eventLog1.WriteEntry("reading data");
}
}
else
{
eventLog1.WriteEntry("No rows found.");
}
reader.Close();
}
}
catch (Exception e)
{
eventLog1.WriteEntry("Error Message: " + e.Message);
}
}
订阅了SqlDependency
事件,如下所示:
private void Dependency_OnChange(object sender, SqlNotificationEventArgs e)
{
// Handle the event.
eventLog1.WriteEntry("data changed");
}
OnStop()
方法如下所示:
protected override void OnStop()
{
SqlDependency.Stop(connstr);
connection.Close();
eventLog1.WriteEntry("In onStop.");
}
我在数据库中将ENABLE_BROKER
设置为true。 最终结果是,该服务运行,并创建了以下日志:
"Service Started"
"permission granted"
"data changed"
但是,当我将新数据插入表中时,不会触发OnChange()
事件,也不会创建新日志。 同样,当我停止并再次启动该服务时,即使没有插入新数据,也会触发OnChange()
。
谁能帮助我了解这一过程?
事件触发后将删除SqlDependency,因此您需要再次使用依赖项执行命令。 下面是一个控制台应用程序示例,除非由于错误通知,否则该示例将再次订阅。
using System;
using System.Data;
using System.Data.SqlClient;
namespace SqlDependencyExample
{
class Program
{
static string connectionString = @"Data Source=.;Initial Catalog=YourDatabase;Application Name=SqlDependencyExample;Integrated Security=SSPI";
static void Main(string[] args)
{
SqlDependency.Start(connectionString);
getDataWithSqlDependency();
Console.WriteLine("Waiting for data changes");
Console.WriteLine("Press enter to quit");
Console.ReadLine();
SqlDependency.Stop(connectionString);
}
static DataTable getDataWithSqlDependency()
{
using (var connection = new SqlConnection(connectionString))
using (var cmd = new SqlCommand("SELECT Col1, Col2, Col3 FROM dbo.MyTable;", connection))
{
var dt = new DataTable();
// Create dependency for this command and add event handler
var dependency = new SqlDependency(cmd);
dependency.OnChange += new OnChangeEventHandler(onDependencyChange);
// execute command to get data
connection.Open();
dt.Load(cmd.ExecuteReader(CommandBehavior.CloseConnection));
return dt;
}
}
// Handler method
static void onDependencyChange(object sender,
SqlNotificationEventArgs e)
{
Console.WriteLine($"OnChange Event fired. SqlNotificationEventArgs: Info={e.Info}, Source={e.Source}, Type={e.Type}.");
if ((e.Info != SqlNotificationInfo.Invalid)
&& (e.Type != SqlNotificationType.Subscribe))
{
//resubscribe
var dt = getDataWithSqlDependency();
Console.WriteLine($"Data changed. {dt.Rows.Count} rows returned.");
}
else
{
Console.WriteLine("SqlDependency not restarted");
}
}
}
}
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