通过 Sql 服务器数据库更改通知 winforms 应用程序

Question

我创建了一个 Sql 服务器数据库，我在其中添加了一个名为 user 的 table。然后我执行了这个脚本

ALTER DATABASE [TestNotification] SET ENABLE_BROKER

我想在 user table 更改时使用 SqlDependency class 通知 winforms 应用程序。

 namespace Watcher
{
    public partial class Form1 : Form
    {
        private int changeCount = 0; 
        private const string statusMessage = "{0} changes have occurred."; 
        private DataSet dataToWatch = null;
        private SqlConnection connection = null;
        private SqlCommand command = null;

        public Form1()
        {
            InitializeComponent();
            button1.Enabled = CanRequestNotifications();
            this.FormClosed += Form1_FormClosed;
        }

        void Form1_FormClosed(object sender, FormClosedEventArgs e)
        {
            SqlDependency.Stop(GetConnectionString());
            if (connection != null)
            {
                connection.Close();
            }
        }

        private bool CanRequestNotifications()
        {
            // In order to use the callback feature of the
            // SqlDependency, the application must have
            // the SqlClientPermission permission.
            try
            {
                SqlClientPermission perm =
                    new SqlClientPermission(
                    PermissionState.Unrestricted);

                perm.Demand();

                return true;
            }
            catch
            {
                return false;
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {

            changeCount = 0;
            label1.Text = String.Format(statusMessage, changeCount);
            //SqlDependency.Stop(GetConnectionString());
            SqlDependency.Start(GetConnectionString());

            if (connection == null)
            {
                connection = new SqlConnection(GetConnectionString());
            }

            if (command == null)
            {
                command = new SqlCommand(GetSQL(), connection);
            }
            if (dataToWatch == null)
            {
                dataToWatch = new DataSet();
            }

            GetData();

        }

        private string GetConnectionString()
        {
            return @"Data Source=BILOG-PRT-12\SQLEXPRESS; Initial Catalog=TestNotification;Integrated Security=True";
        }

        private string GetSQL()
        {
            return "Select   [id],[nom],[prenom],[age]  from   [dbo].[user]";
        }


        private void dependency_OnChange(object sender, SqlNotificationEventArgs e)
        {

            MessageBox.Show("modification Occurred");
            ISynchronizeInvoke i = (ISynchronizeInvoke)this;
            if (i.InvokeRequired)
            {
                OnChangeEventHandler tempDelegate =new OnChangeEventHandler(dependency_OnChange);
                object[] args = { sender, e };
                i.BeginInvoke(tempDelegate, args);
                return;
            }

            SqlDependency dependency = (SqlDependency)sender;
            dependency.OnChange -= dependency_OnChange;
            ++changeCount;
            label1.Text = String.Format(statusMessage, changeCount);
             GetData();

        }
        private void GetData()
        {

            //dataToWatch.Clear();
            //command.Notification = null;
            SqlDependency dependency = new SqlDependency(command);
            if (connection.State != ConnectionState.Open) connection.Open();
            using (var dr = command.ExecuteReader())
            {
                dependency.OnChange += new OnChangeEventHandler(dependency_OnChange);
            }

        }



    }
}

所有经纪服务运行 :

我启动了应用程序，然后单击按钮，最后进入 Sql 服务器管理工作室 我插入了一个新行。问题是应用程序中的消息框未显示，因此 SQL 服务器未通知 c# 应用程序！！！

所以我需要知道:

为什么会这样？
我忘了哪一步了？
我该如何解决这个问题？

Answer 1

SqlDependency 有很多限制。引用一个相关问题：

The projected columns in the SELECT statement must be explicitly stated, and table names must be qualified with two-part names.Notice that this means that all tables referenced in the statement must be in the same database.

（完整列表请参阅 https://msdn.microsoft.com/library/ms181122.aspx）

您必须明确使用由两部分组成的名称（例如 dbo.user 而不仅仅是 user）。

还有，你需要执行命令。它不只是开始自动工作 :) 添加一个简单的 using (var dr = command.ExecuteReader()) {} 就足够了。

通过 Sql 服务器数据库更改通知 winforms 应用程序

Notify winforms application by Sql Server database changes

.net

c#

sql-server

sqldependency

winforms