wpf单选按钮的验证规则

Question

I have a RadioButton inside ItemsControl . By default Radio Buttons will be unchecked. I want the user to select either of the radio buttons if a particular value (string value) is configured in another screen. I need to apply a validation rule for the same. If the user does not select either of the radio buttons, then on click on a submit button, I should display validation error.

XAML

<StackPanel Grid.Row="1" Visibility="{Binding Path=IsUpdateSendDateConfigured}" Orientation="Horizontal" Margin="0,2,0,0">
        <TextBlock Text="{Binding Path=UpdateSendDate, UpdateSourceTrigger=PropertyChanged}" FontWeight="Bold" FontSize="12" Width="400" TextWrapping="WrapWithOverflow" />
        <ItemsControl Name="updateSendDateLevelItemsControl" ItemsSource="{Binding UpdateSendDateLevel}" Margin="10,5,0,10">
                 <ItemsControl.ItemsPanel>
                         <ItemsPanelTemplate>
                                <StackPanel Orientation="Horizontal"/>
                         </ItemsPanelTemplate>
                 </ItemsControl.ItemsPanel>
                 <ItemsControl.ItemTemplate>
                         <DataTemplate>
                                <RadioButton Height="25" GroupName="updateSendDateLevel" IsChecked="{Binding Selected, ValidatesOnDataErrors=True}" Padding="10,0,10,0" >  <!--Need to apply Validation rule here -->
                                       <TextBlock Text="{Binding Description}"/>
                                </RadioButton>
                         </DataTemplate>
                  </ItemsControl.ItemTemplate>
        </ItemsControl>
</StackPanel>

UpdateSendDateLevel is a view model which I am updating in the controller.

if (!string.IsNullOrEmpty(configuredUpdateDueDateSelection))
{
       UpdateSendDateViewModel updateSendDateLevelViewModel = null;
       foreach (SendDate value in Enum.GetValues(typeof(SendDate)).Cast<SendDate>())
       {
             updateSendDateLevelViewModel = new UpdateSendDateViewModel();
             updateSendDateLevelViewModel.UpdateSendDateLevel = value;
             updateSendDateLevelViewModel.Description = EnumHelper.GetDescription(value);

             m_sendDataContext.UpdateSendDateLevel.Add(updateSendDateLevelViewModel);
        }

} 

Can someone please help with with adding xaml side validation rule or point me in the right direction?

Let me know if you need any other details.

Answer 1

ValidationRules can be added as an extension of the Binding property, like so:

<RadioButton>
    <TextBlock Text="{Binding Description}"/>
    <RadioButton.IsChecked>
        <Binding Path="Selected" UpdateSourceTrigger="PropertyChanged">
          <Binding.ValidationRules>
            <rules:YourValidationRule Min="21" Max="130"/>
          </Binding.ValidationRules>
        </Binding>
    </RadioButton.IsChecked>
</RadioButton>

(Note for the above that you don't actually need to use a TextBlock if all you're doing is putting text in the block. You can just include that text binding in the Content="" field on the RadioButton.)

Then you'd also need to define an object (YourValidationRule) that inherits from ValidationRule and overrides public ValidationResult Validate(object value, CultureInfo cultureInfo), and add a static reference (rules, in this case) to the namespace in which your custom ValidationRule exists.

An in-depth tutorial for ValidationRules exists on MSDN at this link: http://msdn.microsoft.com/en-us/library/ms753962%28v=vs.110%29.aspx

However, Miiko is correct - it may be easier for you to use an object that implements ICommand, and use CanExecute to determine whether the customer may proceed. The main downside of this is that a ghosted, unusable button is not necessarily communicative, and you should be careful to ensure that your customers understand why they're unable to use the button.