当每分钟尝试调用方法时，它只调用两次

Question

当我在 form_load 中调用 ScheduleBackUp() 时，方法只执行两次！

这是我的 class:

class BackupDBs : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        private readonly object _lock = new object();
        private int _state = -1;
        string nameBackupFolder;    

        public void ScheduleBackUp()
        {
            var startTimeSpan = TimeSpan.Zero;
            var periodTimeSpan = TimeSpan.FromMinutes(1);

            var timer = new System.Threading.Timer((e) =>
            { 
                DoBackup();
            }, null, startTimeSpan, periodTimeSpan);

        }

        public int MyState
        {
            get
            {
                return _state;
            }
            set
            {
                lock (_lock)
                {
                    if (value != _state)
                    {
                        _state = value;
                        NotifyStateChanged("MyState");
                    }
                }
            }
        }

        private void NotifyStateChanged(string propertyName)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

        public void DoBackup()
        {
            MyState = 0;

            try
            {
                MyState = 1;
                MyState = 2;
                CreateBackupFolder();
            }
            catch
            {
                MyState = 3;                
                return;
            }

            try
            {
                var con = new MainCon();
                con.sqlQuery("BACKUP DATABASE [" + DataCenter.DEFAULT_DB_NAME + "] TO DISK='" + nameBackupFolder + "\" + DataCenter.DEFAULT_DB_NAME + "-" + DateTime.Now.ToString("yyyy-MM-dd--HH-mm-ss") + ".bak'");

                con.nonQueryEx();
                con.closecon();

                MyState = 4;
            }
            catch
            {
                MyState = 5;                
            }
        }

 public void CreateBackupFolder()
        {
            //couz we need create to each DB special folder so we need to get the descr of default DB           
            string desc = DataCenter.DEFAULT_DB_DESCRIPTION;

            //Get the default path for backup
            string pathBackup = DataCenter.BACKUP_PATH;

            //Preaper the name for our folder
            nameBackupFolder = pathBackup + @"\" + "backup for " + desc;

            // Create a new target folder, if not exists.
            if (!System.IO.Directory.Exists(nameBackupFolder))
            {
                System.IO.Directory.CreateDirectory(nameBackupFolder);
            }
        }

我用这个来调用方法:

private Classes.BackupDBs budb = new Classes.BackupDBs();
budb.ScheduleBackUp();

刚刚发生了两次成功的备份然后什么都没有发生。请问我错过了什么？

Answer 1

您只需将 timer 的声明移至您的表单字段，这样它就不会超出范围并被回收。

您的字段应如下所示：

public event PropertyChangedEventHandler PropertyChanged;
private readonly object _lock = new object();
private int _state = -1;
string nameBackupFolder;    

System.Threading.Timer timer;

现在 ScheduleBackup()，执行：

timer = new System.Threading.Timer((e) =>
{ 
    DoBackup();
}, null, startTimeSpan, periodTimeSpan);

现在它将永远有效。

当每分钟尝试调用方法时，它只调用两次

When try call method every minute it called just twice

c#

timespan