Maintain selected value of RadCombox

[Jackey]

Hi guys,

I am try my best to make myself clear. I have two pages with one of them being Config page. In the config page, I have a RadCombox to choose a time span value. The code snippets are below.

<telerik:RadComboBox Width="125" FontSize="{DynamicResource FontSizeBig}"
        VerticalAlignment="Center" Height="32" Margin="0,0,5,0" SelectedValue="{Binding Realtime.TimeRemaining, Converter={StaticResource DetectionDurationConverter}, Source={StaticResource Locator}}">
              <telerik:RadComboBoxItem Content="10 s" />
              <telerik:RadComboBoxItem Content="10 minutes"/>
              <telerik:RadComboBoxItem Content="1 hour"/>
              <telerik:RadComboBoxItem Content="Custom" Margin="0"/>
</telerik:RadComboBox>

As you can see from the above code, I binds the selected value to TimeRemaing property and I would use a customized converter named DetectionDurationConverter to turn 10 s, 10 minutes and 1 hour into a time span value in C#.  Here is my converter. 

public class DetectionDurationConverter : IValueConverter
{
    private static readonly string[] durationSet = new[] {"10 s", "10 minutes", "1 hour"};

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var timeSpan = (TimeSpan) value;
        if (timeSpan == TimeSpan.FromSeconds(10.0))
        {
            return durationSet[0];
        } else if (timeSpan == TimeSpan.FromMinutes(10.0))
        {
            return durationSet[1];
        } else if (timeSpan == TimeSpan.FromHours(1.0))
        {
            return durationSet[2];
        }
        return string.Empty;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var timeSpan = TimeSpan.MinValue;
        if (value is RadComboBoxItem)
        {
            var val = System.Convert.ToString((value as RadComboBoxItem).Content);
            if (val == durationSet[0])
            {
                timeSpan = TimeSpan.FromSeconds(10.0);
            }
            else if (val == durationSet[1])
            {
                timeSpan = TimeSpan.FromMinutes(10.0);
            }
            else if (val == durationSet[2])
            {
                timeSpan = TimeSpan.FromHours(1.0);
            }
        }
        return timeSpan;
    }
}

For example, when I select a '10 s', it goes to ConvertBack method as expected and TimeRemaining is a 10 second time span value. Then I switched to another page and switched back, it goes to Convert method with TimeRemaining being 10 seonds still. Note, the method Convert would be entered twice. However, in the UI, no items have been selected. I just hope the selected item would be consistent with the value of TimeRemaining.

Thanks,
-J

[Jackey]

Somebody helps me to move this thread to Combox forum. Thanks a lot!

[Nasko]

Hello Jingfei,

What I can suggest you in order to achieve the desired functionality would be to bind the ItemsSource of the ComboBox to a collection of objects instead of using static RadComboBoxItems:

http://www.telerik.com/help/wpf/radcombobox-populating-with-data-binding-to-object.html

The reason why the converter does not work properly is because it returns objects of type string while it is expected to return RadComboBoxItem and thus in the UI no items would be selected.

I hope this information will help you.

Regards,
Nasko
Telerik

 

 

[Jackey]

Hi Nasko,

Thanks very much for your reply. I would take your suggestion then.
For expanding my knowledge, I still want to know how to return a RadComboBoxItem object to make the converter work?  Following code also didn't work.

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    var boxItem = new RadComboBoxItem();
    var timeSpan = (TimeSpan) value;
    if (timeSpan == TimeSpan.FromSeconds(10.0))
    {
        boxItem.Content = durationSet[0];
    } else if (timeSpan == TimeSpan.FromMinutes(10.0))
    {
        boxItem.Content = durationSet[1];
    } else if (timeSpan == TimeSpan.FromHours(1.0))
    {
        boxItem.Content = durationSet[2];
    }
    return boxItem;
}

Thanks,
-J

[Nasko]

Hi Jingfei,

That implementation of the Convert method in this case could not work properly due to the fact that it should return the instance of the required item instead of a newly created RadComboBoxItem. However I recommend you to use the the approach I suggested you it the previous response.

Please do not hesitate to contact us if you have any additional questions.

Regards,
Nasko
Telerik

 

 

[Jackey]

Thanks a lot, Nasko.

I know what I should do now.