private void buttonAdd_Click(object sender, EventArgs e)
        {
            if (this.textBoxActivityName.Text == string.Empty)
            {
                this.labelError.Text    = Constants.ACTIVITY_NAME_EMPTY;
                this.labelError.Visible = true;
            }
            else if (this.numericUpDownActivityCost.Value < 0)
            {
                this.labelError.Text    = Constants.ACTIVITY_COST_NEGATIVE;
                this.labelError.Visible = true;
            }
            else
            {
                try
                {
                    this.labelError.Visible = false;

                    var activityToAdd = new Activity();
                    activityToAdd.Name = this.textBoxActivityName.Text;
                    activityToAdd.Cost = (int)this.numericUpDownActivityCost.Value;
                    activityToAdd.Date = dateTimePickerActivityDate.Value;

                    IActivityLogic activitiesOperations = Provider.GetInstance.GetActivityOperations();
                    activityToAdd.Id = activitiesOperations.GetNextActivityNumber();
                    activitiesOperations.AddActivity(activityToAdd);
                    this.CleanForm();
                    this.labelSuccess.Text = Constants.SUCCESS_ACTIVITY_REGISTRATION;
                }
                catch (CoreException ex)
                {
                    labelError.Text = ex.Message;
                }
            }