/// <summary>
        /// open existing database
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void OpenToolStripMenuItem_Click(object sender, EventArgs e)
        {
            //close opened database
            this.CloseToolStripMenuItem.PerformClick();

            string filename = "";

            //get database location
            using (OpenFileDialog dialog = new OpenFileDialog())
            {
                dialog.Title            = "Open database";
                dialog.InitialDirectory = Application.StartupPath;
                dialog.Filter           = "SQLite database | *.db";
                dialog.ShowDialog(this);

                if (dialog.FileName.Trim() != "")
                {
                    filename = dialog.FileName.Trim();
                }
            }

            //open database
            if (filename.Trim() != "")
            {
                this._Database = new Database.SQLiteDatabase(filename);

                //check master password
                bool MasterPassword = false;
                while (true)
                {
                    using (MasterPasswordForm master = new MasterPasswordForm(this._Database))
                    {
                        master.ShowDialog(this);
                        if (master.DialogResult == DialogResult.OK)
                        {
                            if (master.IsValid() == true)
                            {
                                this._MasterPassword = master.GetMasterPassword();
                                MasterPassword       = true;
                                break;
                            }
                        }
                        else
                        {
                            break;
                        }
                    }
                }

                //if master password true, show all account
                if (MasterPassword == true)
                {
                    //this.AccountTable.DataSource = this._Database.LoadAccount();
                    this._Database.LoadAccount(ref this.AccountTable);
                }
            }
        }
        /// <summary>
        /// create new database
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void NewToolStripMenuItem_Click(object sender, EventArgs e)
        {
            //close opened database
            this.CloseToolStripMenuItem.PerformClick();

            bool new_database = false;

            using (MasterPasswordForm master = new MasterPasswordForm())
            {
                while (true)
                {
                    master.ShowDialog(this);
                    if (master.DialogResult == DialogResult.OK)
                    {
                        if (master.PasswordRequiment() == true)
                        {
                            this._MasterPassword = master.GetMasterPassword();
                            new_database         = true;
                            break;
                        }
                    }
                    else
                    {
                        break;
                    }
                }
            }

            string filename = "";

            if (new_database == true)
            {
                //create new database
                using (SaveFileDialog dialog = new SaveFileDialog())
                {
                    dialog.Title            = "Save database";
                    dialog.InitialDirectory = Application.StartupPath;
                    dialog.Filter           = "SQLite database | *.db";
                    dialog.ShowDialog(this);

                    if (dialog.FileName.Trim() != "")
                    {
                        filename = dialog.FileName.Trim();
                    }
                }
            }

            if (filename != "")
            {
                try
                {
                    if (System.IO.File.Exists(filename))
                    {
                        System.IO.File.Delete(filename);
                    }
                }
                catch
                {
                    MessageBox.Show("Can't replace the file.");
                    return;
                }

                //Database.SQLiteDatabase.CreateDatabase(dialog.FileName);
                this._Database = new Database.SQLiteDatabase();
                this._Database.CreateDatabase(filename);
                this._Database = new Database.SQLiteDatabase(filename);
                this._Database.CreateQPassDatabase(this._MasterPassword);

                //show account list
                this._Database.LoadAccount(ref this.AccountTable);
            }
        }