当数据集被改变的SqlDependency不会触发OnChange事件(SqlDependency

我是新来的查询通知与SQL Server的概念，这将需要一些时间对我来说，环绕它我的头。

我的目标是创建时的变化已经到SQL Server表作出通知Windows服务的应用程序。 我跟着这个指南，是让我开始有帮助的。

但是我没能获得预期的结果。 的OnStart()在我的Windows服务应用方法看起来像这样：

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);
        }
}

该事件SqlDependency订阅了，看起来就像这样：

private void Dependency_OnChange(object sender, SqlNotificationEventArgs e)
{
    // Handle the event.
    eventLog1.WriteEntry("data changed");
}

该OnStop()方法看起来像这样：

protected override void OnStop()
{
        SqlDependency.Stop(connstr);
        connection.Close();
        eventLog1.WriteEntry("In onStop.");
}

我有ENABLE_BROKER设置为true在我的数据库。 最终的结果是，该服务运行及以下日志创建：

"Service Started"
"permission granted"
"data changed"

然而，当我把新数据插入表中， OnChange()事件不火而没有创建新日志。 此外，当我再次停止和启动服务时， OnChange()是即使有插入没有新的数据触发。

谁能帮我理解这个过程？

Answer 1:

所以你需要与依赖再次执行命令的SqlDependency是事件触发后取出。 下面是一个控制台应用程序例如除非通知是由于一个错误，将重新订阅。

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");
            }

        }


    }
}

文章来源: SqlDependency doesn't fire OnChange event when dataset is changed