private void Datepicker_Unfocused(object sender, FocusEventArgs e)
        {
            string textValue = ((Entry)sender).ValidatedText();
            bool   isValid   = IsRequired ? !string.IsNullOrWhiteSpace(textValue) : true;

            IsValid = Validators.DateStringValidator(textValue) && isValid;
            ((Entry)sender).TextColor = IsValid ? DefaultColor : ErrorColor;
        }