ComboBox SelectedItem binding not updating

Question

I'm a bit puzzled: this works:

<StackPanel Orientation="Horizontal" HorizontalAlignment="Right">
            <Label Content="Rol" />
            <ComboBox ItemTemplate="{StaticResource listRollen}"
                      Height="23" Width="150"
                      SelectedItem="{Binding Path=SelectedRol, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"
                      ItemsSource="{Binding Path=allRollen, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
        </StackPanel>

and the property for SelectedRol is:

public TblRollen SelectedRol
    {
        get { return _selectedRol; }
        set
        {
            if (_selectedRol != value)
            {
                _selectedRol = value;
                OnPropertyChanged("SelectedRol");
            }
        }
    }

But this doesn't work:

<StackPanel Orientation="Horizontal" HorizontalAlignment="Right">
            <Label Content="Soort" />
            <ComboBox ItemTemplate="{StaticResource listSoorten}"
                      Height="23" Width="150"
                      ItemsSource="{Binding Path=allSoorten}"
                      SelectedItem="{Binding Path=SelectedProduct, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
        </StackPanel>

with following property SelectedProduct:

public TblProduktSoorten SelectedProduct
    {
        get { return _selectedPSoort; }
        set
        {
            if (_selectedPSoort != value)
            {
                _selectedPSoort = value;
                OnPropertyChanged("SelectedProduct");
            }
        }
    }

somewhere in my code I set SelectedProduct = p.TblProduktSoorten and while debugging, I see the property gets set correctly...

Sorry. Went about too quickly. the combobox for the SelectedRol correctly displays the property when the property gets a new value (from a selectionChanged event in a listbox) However, with almost exactly the same code, the SelectedPSoort combobox never displays anything. The ItemsSource works, the SelectedItem gets filled but doesn't display in the combobox. If that makes sense... — olvr_vrmr, Jun 03 '11 at 11:29
Don't you have to use the Mode=TwoWay for the ItemsSource as well (as in the working sample)? — Gorgsenegger, Jun 03 '11 at 11:33
Are you sure your ItemsSource contains objects of type TblProduktSoorten? Because if not you will not get any error on SelectedItem binding. — Dummy01, Jun 03 '11 at 11:40
My ItemsSource is `ObservableCollection allSoorten = new ObservableCollection(pRep.Service.GetAll());` — olvr_vrmr, Jun 03 '11 at 11:42
Bindings only work against properties, not fields (http://stackoverflow.com/questions/842575/why-does-wpf-support-binding-to-properties-of-an-object-but-not-fields) — CodeNaked, Jun 03 '11 at 11:45

score 15 · Answer 1 · edited Jun 20 '20 at 09:12

15

Combobox inside a DataGrid?

If the combobox is in a DataGrid you must add this :

Mode=TwoWay, UpdateSourceTrigger=PropertyChanged

See this : https://stackoverflow.com/a/5669426/16940

edited Jun 20 '20 at 09:12

Community

1
1

answered Aug 22 '17 at 01:27

Simon_Weaver

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Same for some other controls too like `RadioButton`. Not sure the exact criteria or why this is necessary. May be something to do with the visual tree hierarchy or something like that. – Simon_Weaver Oct 25 '17 at 08:46

score 7 · Answer 2 · answered Jun 03 '11 at 11:32

7

Try to use not selected item but value path look at the code sample

<ComboBox Name="projectcomboBox" ItemsSource="{Binding Path=Projects}" IsSynchronizedWithCurrentItem="True" DisplayMemberPath="FullName"
          SelectedValuePath="Name"  SelectedIndex="0"  Grid.Row="1" Visibility="Visible" Canvas.Left="10" Canvas.Top="24" Margin="11,6,13,10">
</ComboBox>

the binding property is

public ObservableCollection<Project> Projects
{
    get { return projects; }
    set
    {
        projects = value;
        RaisePropertyChanged("Projects");
    }
}

answered Jun 03 '11 at 11:32

Sergey K

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IsSynchronizedWithCurrentItem="True" helped me. Thx – RDV Sep 26 '16 at 22:31
@RDV ouugh this solved my issue as well! For me, the update worked, but only at _every other_ selection! I don't know what this weirdness has caused. But adding `IsSynchronizedWithCurrentItem="True"`, solved this and the binding update works with every update now! – Nicolas Oct 25 '18 at 09:49
@RDV if you would take a look in the code I've provided there is IsSynchronizedWithCurrentItem="True" set up – Sergey K Apr 19 '23 at 20:04
Yes, that was the only thing missing from my code, and I thanked you for that. – RDV Apr 21 '23 at 23:38

score 6 · Answer 3 · answered Jan 15 '20 at 22:51

6

My problem was caused by my own tired brain. Same symptom, maybe it will kick you into seeing your problem.

Setting the SelectedItem must be given an item in the List!! (duhh) Normally this happens naturally but I had a case I got a "Role" from another service (Same object type) and was trying to set it and expecting the combobox to change! ;(

instead of -

Roles = roles;
CurrentRole = role;

remember to do this -

Roles = roles;
CurrentRole = roles.FirstOrDefault(e=> e.ID == role.ID); //(System.Linq)

answered Jan 15 '20 at 22:51

HD28

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made that same mistake! already had that inkling that this might be the rootcause in the beginning, still searched the web for an hour until I saw your answer, lol – drkthng Jan 05 '21 at 21:32
Just had the same mistake. Glad I found your post. – Athanasios Emmanouilidis Oct 14 '22 at 12:45

score 6 · Answer 4 · edited May 23 '17 at 12:19

6

This might be related to the fact that apparently attribute order does matter, in your second case the ItemsSource and SelectedItem declarations are swapped.

edited May 23 '17 at 12:19

Community

1
1

answered Jun 03 '11 at 12:26

H.B.

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I have to say I think this is total nonsense for a properly tested component. It *may* be technically possible (I'm still not convinced about that) but you should *never* have to worry about this for Microsoft controls. – Simon_Weaver Aug 22 '17 at 01:27

score 3 · Answer 5 · answered Apr 17 '19 at 08:49

If you set the SelectedProduct property when SelectedProduct is changed in the property changed event handler, you need to set this property asynchronously.

private void ViewModel_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
    if (e.PropertyName == "SelectedProduct")
        App.Current.Dispatcher.InvokeAsync(() => SelectedProduct = somevalue);
}

score 2 · Answer 6 · answered Apr 09 '18 at 15:08

2

I don't know if you fixed it yet, but I encountered the same issue today. It was fixed by making sure the collection for selecteditems was an ObservableCollection.

answered Apr 09 '18 at 15:08

A. Don

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6

I tried all the other answers to no avail. This answer worked for me. Short and sweet. – rr789 Mar 17 '20 at 23:17

score 2 · Answer 7 · answered Feb 19 '21 at 10:20

I think this problem is caused by the type of ItemSource and SelectedItem is mitchmatched.

For example, if the ItemSource is binded to a List of int and the SelectedItem is binded to a string. If you set selected item to null or empty string, the combobox cannot know what item is selected. So the combobox will show nothing.

score 0 · Answer 8 · answered Nov 01 '22 at 08:12

0

This might be old but I have not seen the trick that did it for me; I had to add NotifyOnSourceupdate=true to my SelectedItem in the ComboBox

answered Nov 01 '22 at 08:12

Pauldb

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score 0 · Answer 9 · answered Dec 16 '22 at 07:00

This had me stumped for a while inside a DataGrid, using SelectedItem. Everything was fine but I am deserializing the app state which loads the items and also has a selected item. The collection was there but the selected isn't actually visible until I used the Text="{Binding Path=Score.SelectedResult.Offset}"

<DataGridTemplateColumn.CellTemplate>
    <DataTemplate>
        <ComboBox ToolTip="Score offset results" 
          ItemsSource="{Binding Score.SearchResults,UpdateSourceTrigger=PropertyChanged}"                                                   
          SelectedItem="{Binding Score.SelectedResult, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
          Text="{Binding Path=Score.SelectedResult.Offset}"
          SelectedValuePath="Offset"
          DisplayMemberPath="Offset"/>
    </DataTemplate>
</DataGridTemplateColumn.CellTemplate>

ComboBox SelectedItem binding not updating

9 Answers9

Combobox inside a DataGrid?