CSLA .NET discussion

Re: Silverlight 4 ComboBox is broken and wasting my time.

Ubuntu — Fri, 12 Apr 2013 00:50:05 GMT

Dear Jaans,

I wounder If you can help to apply this solution for telerik RadComboBox, I tried myself but didn't succeed

Best

Re: Silverlight 4 ComboBox is broken and wasting my time.

Ubuntu — Thu, 11 Apr 2013 23:56:40 GMT

Dear Jaans,

I was preparing a repo to send to you, when I suddenly descoverd the issue !!!

It was the Region combo, I was using telerik combo for Regions and not your modified one, when I replace the telerik combo with that one, everything worked fine as excpected ...

I now have simple issue, which is when the Govs changed the old selected value in Region combo is still there, but this is easy & can resolve.

Thanks to you, I managed to resolve the Main Big issue.

Best regards

Re: Silverlight 4 ComboBox is broken and wasting my time.

Jaans — Wed, 10 Apr 2013 20:57:20 GMT

@kondamca - Hi

Not much to go on here... could you attach a sample project showing the problem?

Re: Silverlight 4 ComboBox is broken and wasting my time.

kondamca — Wed, 10 Apr 2013 10:03:09 GMT

Hi Jaans,

I have implemented the same, in my scenario based on combobox1 selection my other combobox2 itemsource is getting update. When I am clicking on combobox2 I am getting object reference null exception I am getting

Message: Unhandled Error in Silverlight Application

Code: 4004

Category: ManagedRuntimeError

Message: System.NullReferenceException: Object reference not set to an instance of an object.

at System.Windows.Controls.ItemContainerGenerator.System.Windows.Controls.Primitives.IItemContainerGenerator.PrepareItemContainer(DependencyObject container)

at System.Windows.Controls.ComboBox.SetContentPresenter(Int32 index)

at System.Windows.Controls.ComboBox.OnIsDropDownOpenChanged(Boolean isDropDownOpen)

at System.Windows.Controls.ComboBox.OnIsDropDownOpenChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)

at System.Windows.DependencyObject.RaisePropertyChangeNotifications(DependencyProperty dp, Object oldValue, Object newValue)

at System.Windows.DependencyObject.UpdateEffectiveValue(DependencyProperty property, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, ValueOperation operation)

at System.Windows.DependencyObject.SetValueInternal(DependencyProperty dp, Object value, Boolean allowReadOnlySet, Boolean isBindingInStyleSetter)

at System.Windows.DependencyObject.SetValue(DependencyProperty property, Boolean b)

at System.Windows.Controls.ComboBox.ElementDropDownToggle_Click(Object sender, RoutedEventArgs e)

at System.Windows.Controls.Primitives.ButtonBase.OnClick()

at System.Windows.Controls.Primitives.ToggleButton.OnClick()

at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)

at System.Windows.Controls.Control.OnMouseLeftButtonUp(Control ctrl, EventArgs e)

at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName, UInt32 flags)

Can you please help me out what can be the issue for this exception.

Thanks in advance

Re: Silverlight 4 ComboBox is broken and wasting my time.

Jaans — Tue, 09 Apr 2013 21:16:59 GMT

Admittedly, I can't clearly see a culprit, but there are some possibilities.

Please note that binding to *only* the SelectedItem (not just changing the BindingMode of SelectedValueProper to OneWay) has always worked correctly for the standard combo box and does not require the workaround posted in this thread. This scenario of binding to SelectedItem is very effective when you need the full object of the item selected in the combo box, but you have to do extra work to use the value. I often use DependencyProperty for my SelectedItem binding targets and then utilise the PropertyChangedEvent of those to do the 'extra work'.

However, if you instead require binding of a property (on the object of the selected item), then this ComboBoxEx workaround might help by using SelectedValueProper.

From the above it would seem that you are mixing the two. You could consider using just the one or the other. From the above, you are binding both the CurrentItem.MgovID property to SelectedValueProper and the SelectedGov property to SelectedItem on the combobox, and both are trying to influence the combo box.

Furthermore, the code that sets SelectedGov is getting a different instance of the Goverment class. Remember, just because the MgovID's match doesn't mean it's the same object, just an equivalent one. If you are using the SelectedItem binding this will be a problem because you need to be using the same instance as that which is present in the combo box's ItemSource collection.

If you are using SelectedValueProper scenario, then you don't need the SelectedGov nor do you need to look it up against the data source again (possibly an expensive database hit). It (the ComboBoxEx) should be using the CurrentItem.MgovID value to lookup the matching Government instance, and 'preselect' the correct item for you.

PS: If this is urgent then a working repo would probably be the quickest way for me to help.

Hope that helps,
Jaans

Re: Silverlight 4 ComboBox is broken and wasting my time.

Ubuntu — Tue, 09 Apr 2013 18:18:32 GMT

Dear Jaans,

Appreciate your prompt reply.

I tried and changed the SelectedItem to be Twoway and made the SelectedValueProper Oneway.

Well, I am almost there, It doesn't do the trick first time, but If I continue to change the Gov, Regions changes accordingly.

Here is the Gov item source, it is a telerik QueryableDomainServiceCollectionView here is how I define it in the VM:

private QueryableDomainServiceCollectionView<Government> _gov;

public QueryableDomainServiceCollectionView<Government> Govs

{

get { return _gov; }

set { _gov = value; RaisePropertyChanged(() => Govs); }

}

and I am populating it as follow:

SelectedGov = DataService.GetGovernments().Where(o=>o.ID == CurrentItem.MgovID).FirstOrDefault();

if (Govs!=null) { if (Govs.HasChanges) Govs.RejectChanges(); }

Govs = DataService.GetGovernments();

Govs.AutoLoad = true;

please note that the SelectedGov is binded to the SelectItem from the combo

CurrentItem is defined as follow:

private MasterFile _currentItem;

public MasterFile CurrentItem

{

get{return _currentItem ;}

set { _currentItem = value; RaisePropertyChanged(() => CurrentItem);

}

and I am poupating it using Loadoperation.

Note: If I follow the other solution and make the SelectedItem as Oneway and SelectedValueProper as Twoway and try to populate the region when the Gov changes in the CurrentItem ProperityChanged the value never changed to the newly selected Gov, as if it is stuck and doesn't comply. see the code below:

void CurrentItem_PropertyChanged(object sender, PropertyChangedEventArgs e)

{

var currRecord = (MasterFile)sender;

switch (e.PropertyName)

{

case "MgovID":

if (currRecord.MgovID == null) return;

if (Regions != null) if (Regions.HasChanges) Regions.RejectChanges();

Regions = DataService.GetRegionsByGovId((int)currRecord.MgovID);

Regions.AutoLoad = true;

break;

}

If this is not enough, tell me and I will try to submit you a repo.

Thanks again & best regards

Re: Silverlight 4 ComboBox is broken and wasting my time.

Jaans — Mon, 08 Apr 2013 22:21:11 GMT

At quick glance it could be many things.

One I'm wondering about it that you are using two way binding for both the SelectedItem and the SelectedValueProper. Usually you can bind to the one or the other, but if you bind to both you could get them affecting each other. Try using only the one.

Also, I'm unable to see the code for the item source (ContextProxy's DataSource.Govs) and the code for the target binding (CurrentItem.MgovID) as these could be part of the problem (especially the latter) if it's not implemented as a writable property on a dependency object (ultimately not raising the relevant INPC events).

If you are still stuck, please try and provide a complete sample / code showing the issue, so that I could look at it and see if I can find the issue.

Hth.

Re: Silverlight 4 ComboBox is broken and wasting my time.

Ubuntu — Mon, 08 Apr 2013 18:20:36 GMT

Hello Jaans,

I though this could help me !! but not ... let me explain my issue in details:

I have two comboboxs; the first one is showing the Countries, based on its selection the second combo is showing list of Regions, this is how i define the Countries(Gov) combo in xaml:

<Infrastructure:ComboBoxEx x:Name="cbxMGov" Margin="0,0,0,5" Grid.Row="6" Grid.Column="1" Grid.ColumnSpan="4"

ItemsSource="{Binding Source={StaticResource ContextProxy},Path=DataSource.Govs,NotifyOnValidationError=True,ValidatesOnExceptions=True}" MaxDropDownHeight ="120"

SelectedValuePath ="ID" SelectedValueProper="{Binding Path=CurrentItem.MgovID, Mode=TwoWay,NotifyOnValidationError=True,ValidatesOnExceptions =True}" DisplayMemberPath ="Name"

SelectedItem="{Binding Source={StaticResource ContextProxy},Path=DataSource.SelectedGov,Mode=TwoWay}">

<i:Interaction.Triggers>

<i:EventTrigger EventName ="SelectionChanged">

<i:InvokeCommandAction Command="{Binding SelectionChangedGovCommand}" CommandParameter="{Binding SelectedItem, ElementName=cbxMGov}" />

</i:EventTrigger>

</i:Interaction.Triggers>

</Infrastructure:ComboBoxEx>

Here is; when the user select or change his selection in the combobox, I use the SelectedGov to retrieve the Regions based on the selection, the SelectedValueProper should hold the current ID of the selected Country. and store it in the CurrentItem.MgovID.

This scenario works okay when I create a new record, but when I try to updated an existing record and change the country from the combobox, it doesn't accept any changes and keep the selection of the first selected country !!!

What could be the reason of this.

I hope I explained the issue, please advise if more information is needed

Best regards

Re: Silverlight 4 ComboBox is broken and wasting my time.

jason.liao — Thu, 21 Mar 2013 08:17:07 GMT

A quick solution is, store the selected item in a tempure var, then restore the item from it.

Re: Silverlight 4 ComboBox is broken and wasting my time.

cshenbagaraj — Thu, 15 Dec 2011 03:12:32 GMT

I can use this getting selected value is working fine but i need selectionChanged for my own use. i hae functionalities using selectionchanged in my project. And also when i use this im receiving an error

"Failed to assign to property 'System.Windows.FrameworkElement.Style'. [Line: 279 Position: 240]"

can u help me out...

Re: Silverlight 4 ComboBox is broken and wasting my time.

Tim — Wed, 03 Aug 2011 02:37:05 GMT

I wanted to provide an update on something I found related to Jaans' fix. While using his solution, I came across an issue in SL4/CSLA 4.1 where I would select a combobox item from the list but the item would not appear as the selected item. If I selected the same item a second time, it finally appeared as selected. In addition, binding was not working...it wouldn't save.

I tried Walk's modification, and it seemed to make the selection issue work correctly (i.e. the first selection made the item actually appear as selected), but two-way binding was still not working. I noticed the other combobox on my usercontrol was working fine with Jaans' code, so I began to look at what was different between the two. Turns out the problem had something to do with binding to a managed property that was defined as a byte. I changed this to an int and everything started working fine.

Re: Silverlight 4 ComboBox is broken and wasting my time.

vvalk — Tue, 19 Apr 2011 13:34:12 GMT

In my project I replaced the original combobox with the extended one and now binding to nullable foreign keys became easy. But I noticed that if ItemsSource of the combo is bound to ICollectionView, CurrentChanged event of the view doesn't get fired...

To handle this situation I modified the ComboBoxEx_SelectionChanged event handler:

private void ComboBoxEx_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            // Avoid recursive stack overflow
            if (_suppressSelectionChangedUpdatesRebind)
                return;
 
            if (e.AddedItems != null && e.AddedItems.Count > 0)
            {
                //SelectedValueProper = GetMemberValue( e.AddedItems[0] );
                SelectedValueProper = SelectedValue; // This is faster than GetMemberValue
                                
                if (this.ItemsSource is ICollectionView)
                    (this.ItemsSource as ICollectionView).MoveCurrentTo(this.SelectedItem);
            }
            // Do not apply the value if no items are selected (ie. the else)
            // because that just passes on the null-value bug from the combobox            
        }

Re: Silverlight 4 ComboBox is broken and wasting my time.

TexMurphy01 — Mon, 11 Apr 2011 15:51:35 GMT

Hi there Jaans,

Wow, okay I'm a bit of a newbie, but your code has saved me a lot of arsing around. All I wanted to do was to be able to update the text that we can see when the combo box is not in drop down mode. Jesus H Christ was that like trying to pull teeth. I was on the Silverlight forums for days... but this fixes it.

I created an account just so I could tell you how grateful I am for this.

Re: Silverlight 4 ComboBox is broken and wasting my time.

cualquiera15 — Fri, 08 Apr 2011 19:41:29 GMT

You just saved me a lot of time. This bug is so annoying. Your fix worked like a charm.

Thanks!!

Re: Silverlight 4 ComboBox is broken and wasting my time.

yesso — Thu, 10 Feb 2011 12:46:51 GMT

i have solved the problem by looking on your old post about the combobox :)

i have changed the code:

        /// <summary>
        /// Sets the selected value suppressing change event processing.
        /// </summary>
        /// <param name="newSelectedValue">The new selected value.</param>
        private void SetSelectedValueSuppressingChangeEventProcessing(object newSelectedValue)
        {
            try
            {
                _suppressSelectionChangedUpdatesRebind = true;
                SelectedValue = newSelectedValue;

                var sel = (from item in this.Items
                           where GetMemberValue(item).Equals(newSelectedValue)
                           select item).SingleOrDefault();

                this.SelectedItem = sel;

            }
            finally
            {
                _suppressSelectionChangedUpdatesRebind = false;
            }
        }

know it works fine...

here my xaml code:

                                     <myctrl:ComboBoxEx x:Name="cmboxSubType"
                                                       DisplayMemberPath="DisplayMember"
                                                       SelectedValuePath="ValueMember"
                                                       SelectedValueProper="{Binding Path=SubType, Mode=TwoWay}"
                                                       ItemsSource="{Binding ElementName=cmboxType, Path=SelectedItem, Converter={StaticResource EnumToComboBoxItemsConverter}, ConverterParameter=SUBTYPE}"
                                                       >
                                    </myctrl:ComboBoxEx>