Develop Reference

Combobox value changes, but visually SelectedValue stays the same

I have a combobox with a custom enum (just true/false). I have a function that checks conditions if the SelectedValue changes from false to true and if the conditions are wrong it changes the combobox SelectedValue back to false. This changes the SelectedValue to false if you check it in code, but when you look at the UI it's still on true.
Here's the xaml for the combobox:
<ComboBox x:Name="comboEnabled1" Width="80" Height="26"
ItemsSource="{Binding Path=TrueFalseChoices}"
SelectedValue="{Binding Path=Enable1, Mode=TwoWay}"/>
Here's the viewmodel
private TrueFalse _enable1 = TrueFalse.False;
public TrueFalse Enable1
{
get { return _enable1; }
set
{
if (_enable1 != value)
{
_enable1 = value;
base.OnPropertyChanged("Enable1");
OnEnableChanged(EventArgs.Empty);
}
}
}
And here's the function that I'm using to check the conditions
public void HandleEnable(object sender, EventArgs e)
{
if(Enable1 == TrueFalse.True)
{
if(!connected)
{
HandleMessage("Can't enable, not connected");
Enable1 = TrueFalse.False;
}
else if (!_main.CBCheck(_main.cbReason))
{
Enable1 = TrueFalse.False;
}
}
Console.WriteLine("Enabled {0}", Enable1);
}
Was thinking I'm changing the value too rapidly, but the last Console.Writeline produces the right outcome each time.
Any help appreciated!
Edit: Calling Handleenable here:
protected void OnEnableChanged(EventArgs e)
{
EventHandler handler = EnableChanged;
if (handler != null)
handler(this, e);
}
And in the ViewModel funct:
EnableChanged += HandleEnable;
Changing the Enable1 in any other place worked as it should have, only having issues in HandleEnable function.Also tried changing other comboboxes in the HandleEnable function and that worked as it should have.

I would recommend actually disabling the ComboBox if the requirements are not met.
But if you insist on reverting Enable1 back to False if conditions are not met, you should push the notification properly through the dispatcher.
set
{
var effectiveValue = condition ? value : TrueFalse.False;
if (effectiveValue == TrueFalse.False && value == TrueFalse.True)
System.Windows.Threading.Dispatcher.CurrentDispatcher.BeginInvoke(
new Action(() => base.OnPropertyChanged("Enable1"), null));
//your regular set-code follows here
}
It happens because WPF is already responding to that event, and therefore ignoring the subsequent calls until it's done. So you immediately queue another pass as soon as the current one is finished.
But I would still recommend disabling the ComboBox when it is effectively disabled. Accessing the dispatcher from a viewmodel does not smell good no matter how you look at it.
UPD: You can also solve that with {Binding Enable1, Delay=10} if your framework is 4.5.1+.

Property bound to DataGrid's SelectedItem does not change its child properties when CellEditEnding is fired

I have a DataGrid which looks like:
<DataGrid Grid.Row="3" Grid.Column="1" ItemsSource="{Binding Purchases}" SelectionMode="Single" SelectionUnit="FullRow"
SelectedItem="{Binding SelectedPurchase, Source={x:Static ex:ServiceLocator.Instance}}"
AutoGenerateColumns="False" CanUserAddRows="False">
<e:Interaction.Triggers>
<e:EventTrigger EventName="CellEditEnding">
<e:InvokeCommandAction Command="{Binding DataContext.CellEditEndingCommand,
RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Page}}}"/>
</e:EventTrigger>
</e:Interaction.Triggers>
<DataGrid.Columns>
.......
........
<DataGrid.Columns>
</DataGrid>
Property SelectedPurchase looks like:
private Purchase _selectedPurchase;
public Purchase SelectedPurchase
{
get
{
return _selectedPurchase;
}
set
{
_selectedPurchase = value;
NotifyPropertyChanged("SelectedPurchase");
}
}
CellEditEndingCommand
public ICommand CellEditEndingCommand { get; set; }
private void CellEditEndingMethod(object obj)
{
XDocument xmlPurchases = XDocument.Load(DirectoryPaths.DataDirectory + "Purchases.xml");
var currentPurchaseInData = (from purchase in xmlPurchases.Element("Purchases").Elements("Purchase")
where Convert.ToInt32(purchase.Attribute("Id").Value) == ServiceLocator.Instance.SelectedPurchase.Id
select purchase).FirstOrDefault();
currentPurchaseInData.SetElementValue("CreditorId", ServiceLocator.Instance.SelectedPurchase.Creditor.Id);
currentPurchaseInData.SetElementValue("AnimalId", ServiceLocator.Instance.SelectedPurchase.Animal.Id);
currentPurchaseInData.SetElementValue("QuantityInLitre", ServiceLocator.Instance.SelectedPurchase.Litre);
currentPurchaseInData.SetElementValue("FAT", ServiceLocator.Instance.SelectedPurchase.FAT);
currentPurchaseInData.SetElementValue("RatePerLitre", ServiceLocator.Instance.SelectedPurchase.RatePerLitre);
xmlPurchases.Save(DirectoryPaths.DataDirectory + "Purchases.xml");
}
Now If I change any value in DataGridCell and then I hit Enter CellEditEndingCommand is fired and CellEditEndingMethod is fired. But If I keep a breakpoint inside CellEditEndingMethod and take a look at it, then I can see that Values of any property of SelectedPurchase does not change to new values.
Let me give an example to explain the above line more correctly:
When I keep a breakpoint on any line inside CellEditEndingMethod and take a look at Properties like Litre, FAT etc., these properties values does not change. I mean I expect the property to take new value but it holds old value. Also, In view I can see the new values but in XML file there are still old values.
Update:
Purchases = new ObservableCollection<Purchase>(
from purchase in XDocument.Load(DirectoryPaths.DataDirectory + "Purchases.xml")
.Element("Purchases").Elements("Purchase")
select new Purchase
{
Id = Convert.ToInt32(purchase.Attribute("Id").Value),
Creditor = (
from creditor in XDocument.Load(DirectoryPaths.DataDirectory + "Creditors.xml")
.Element("Creditors").Elements("Creditor")
where creditor.Attribute("Id").Value == purchase.Element("CreditorId").Value
select new Creditor
{
Id = Convert.ToInt32(creditor.Attribute("Id").Value),
NameInEnglish = creditor.Element("NameInEnglish").Value,
NameInGujarati = creditor.Element("NameInGujarati").Value,
Gender = (
from gender in XDocument.Load(DirectoryPaths.DataDirectory + #"Basic\Genders.xml")
.Element("Genders").Elements("Gender")
where gender.Attribute("Id").Value == creditor.Element("GenderId").Value
select new Gender
{
Id = Convert.ToInt32(gender.Attribute("Id").Value),
Type = gender.Element("Type").Value,
ImageData = gender.Element("ImageData").Value
}
).FirstOrDefault(),
IsRegisteredMember = creditor.Element("IsRegisteredMember").Value == "Yes" ? true : false,
Address = creditor.Element("Address").Value,
City = creditor.Element("City").Value,
ContactNo1 = creditor.Element("ContactNo1").Value,
ContactNo2 = creditor.Element("ContactNo2").Value
}
).FirstOrDefault(),
Animal = (
from animal in XDocument.Load(DirectoryPaths.DataDirectory + #"Basic\Animals.xml")
.Element("Animals").Elements("Animal")
where animal.Attribute("Id").Value == purchase.Element("AnimalId").Value
select new Animal
{
Id = Convert.ToInt32(animal.Attribute("Id").Value),
Type = animal.Element("Type").Value,
ImageData = animal.Element("ImageData").Value,
Colour = animal.Element("Colour").Value
}
).FirstOrDefault(),
Litre = Convert.ToDouble(purchase.Element("QuantityInLitre").Value),
FAT = Convert.ToDouble(purchase.Element("FAT").Value),
RatePerLitre = Convert.ToDouble(purchase.Element("RatePerLitre").Value)
}
);

The CellEditEnding Event is not meant to update the datarow but to validate the single cell and keep it in editing mode if the content is not valid. The real update is done when the whole row is committed. Try it by adding the code in the HandleMainDataGridCellEditEnding method in http://codefluff.blogspot.de/2010/05/commiting-bound-cell-changes.html to your CellEditEndingMethod. It is good explained there. You may replace the if (!isManualEditCommit) {} by if (isManualEditCommit) return;.
UPDATE
You can extend your Purchase class by interface IEditableObject. DataGrid will call the method EndEdit() of this interface after the data has been committed and so you can do the XML stuff there. So you don't need any further buttons because a cell goes in edit mode automatically and the commit is done when you leave the row.
I think the CollectionChanged solution does not work because if you edit a dataset all changes take place inside the single object (Purchase) and not in the collection. CollectionChanged will be called by adding or removing an object to the collection
2nd UPDATE
Another try by putting it all together:
I simplified your Purchase class for demonstration:
class Purchase
{
public string FieldA { get; set; }
public string FieldB { get; set; }
}
Create a derived class to keep the real Purchase class clean:
class EditablePurchase : Purchase, IEditableObject
{
public Action<Purchase> Edited { get; set; }
private int numEdits;
public void BeginEdit()
{
numEdits++;
}
public void CancelEdit()
{
numEdits--;
}
public void EndEdit()
{
if (--numEdits == 0)
{
if (Edited != null)
Edited(this);
}
}
}
This is explained in SO WPF DataGrid calls BeginEdit on an IEditableObject two times?
And create the Purchases collection:
ObservableCollection<EditablePurchase> Purchases = new ObservableCollection<EditablePurchase>()
{
new EditablePurchase {FieldA = "Field_A_1", FieldB = "Field_B_1", Edited = UpdateAction},
new EditablePurchase {FieldA = "Field_A_2", FieldB = "Field_B_2", Edited = UpdateAction}
};
Purchases.CollectionChanged += Purchases_CollectionChanged;
private void Purchases_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.NewItems != null)
foreach (EditablePurchase item in e.NewItems)
item.Edited = UpdateAction;
}
void UpdateAction(Purchase purchase)
{
// Save XML
}
This provides that the calls to Edited are catched for all EditablePurchase elements from initialization and for newly created ones. Be sure to have the Edited property set in initializer

This is a disgrace for WPF. No DataGrid.CellEditEnded event? Ridiculous, and I didn't know about that so far. It's an interesting question.
As Fratyx mentioned, you can call
dataGrid.CommitEdit(DataGridEditingUnit.Row, true);
in a code behind CellEditEnding method. While it works, I find it's quite ugly. Not only because of having code behind (could use a behavior to circumnavigate that), but your ViewModel CellEditEndingMethod will be called twice, once for no good reason because the edit is not yet committed.
I would probably opt to implement INotifyPropertyChanged in your Purchase class (I recommend using a base class so you can write properties on one line again) if you haven't already, and use the PropertyChanged event instead:
public MyViewModel()
{
Purchases = new ObservableCollection<Purchase>();
Purchases.CollectionChanged += Purchases_CollectionChanged;
}
private void Purchases_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.NewItems != null)
foreach (Purchase item in e.NewItems)
item.PropertyChanged += Purchase_PropertyChanged;
if (e.OldItems != null)
foreach (Purchase item in e.OldItems)
item.PropertyChanged -= Purchase_PropertyChanged;
}
private void Purchase_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
// save the xml...
}

You will not get any CollectionChanged event before DataGrid is changing the collection. And this does not before happen a dataset is committed.
If you press 'Enter' in a cell you change the value of this cell in a kind of copy of the real dataset. So it is possible to skip the changes by rollback. Only after finishing a row e.g. by changing to another row or direct commit your changed data will be written back to the original data. THEN the bindings will be updated and the collection is changed.
If you want to have an update cell by cell you have to force the commit as in the code I suggested.
But if you want to have a puristic MVVM solution without code behind you have to be content with the behavior DataGrid is intended for. And that is to update after row is finished.

WPF ListView: Changing ItemsSource does not change ListView

I am using a ListView control to display some lines of data. There is a background task which receives external updates to the content of the list. The newly received data may contain less, more or the same number of items and also the items itself may have changed.
The ListView.ItemsSource is bound to an OberservableCollection (_itemList) so that changes to _itemList should be visible also in the ListView.
_itemList = new ObservableCollection<PmemCombItem>();
_itemList.CollectionChanged += new NotifyCollectionChangedEventHandler(OnCollectionChanged);
L_PmemCombList.ItemsSource = _itemList;
In order to avoid refreshing the complete ListView I do a simple comparison of the newly retrieved list with the current _itemList, change items which are not the same and add/remove items if necessary. The collection "newList" contains newly created objects, so replacing an item in _itemList is correctly sending a "Refresh" notification (which I can log by using the event handler OnCollectionChanged of the ObservableCollection`)
Action action = () =>
{
for (int i = 0; i < newList.Count; i++)
{
// item exists in old list -> replace if changed
if (i < _itemList.Count)
{
if (!_itemList[i].SameDataAs(newList[i]))
_itemList[i] = newList[i];
}
// new list contains more items -> add items
else
_itemList.Add(newList[i]);
}
// new list contains less items -> remove items
for (int i = _itemList.Count - 1; i >= newList.Count; i--)
_itemList.RemoveAt(i);
};
Dispatcher.BeginInvoke(DispatcherPriority.Background, action);
My problem is that if many items are changed in this loop, the ListView is NOT refreshing and the data on screen stay as they are...and this I don't understand.
Even a simpler version like this (exchanging ALL elements)
List<PmemCombItem> newList = new List<PmemCombItem>();
foreach (PmemViewItem comb in combList)
newList.Add(new PmemCombItem(comb));
if (_itemList.Count == newList.Count)
for (int i = 0; i < newList.Count; i++)
_itemList[i] = newList[i];
else
{
_itemList.Clear();
foreach (PmemCombItem item in newList)
_itemList.Add(item);
}
is not working properly
Any clue on this?
UPDATE
If I call the following code manually after updating all elements, everything works fine
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
But of course this causes the UI to update everything which I still want to avoid.

After a change, you can use the following to refresh the Listview, it's more easy
listView.Items.Refresh();

This is what I had to do to get it to work.
MyListView.ItemsSource = null;
MyListView.ItemsSource = MyDataSource;

I know that's an old question, but I just stumbled upon this issue. I didn't really want to use the null assignation trick or the refresh for just a field that was updated.
So, after looking at MSDN, I found this article:
https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.inotifypropertychanged?redirectedfrom=MSDN&view=netframework-4.7.2
To summarize, you just need the item to implement this interface and it will automatically detect that this object can be observed.
public class MyItem : INotifyPropertyChanged
{
private string status;
public string Status
{
get => status;
set
{
OnPropertyChanged(nameof(Status));
status = value;
}
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
So, the event will be called everytime someone changes the Status. And, in your case, the listview will add a handler automatically on the PropertyChanged event.
This doesn't really handle the issue in your case (add/remove).
But for that, I would suggest that you have a look at BindingList<T>
https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.bindinglist-1?view=netframework-4.7.2
Using the same pattern, your listview will be updated properly without using any tricks.

You should not reset ItemsSource of ListView each time observable collection changed. Just set proper binding that will do your trick. In xaml:
<ListView ItemsSource='{Binding ItemsCollection}'
...
</ListView>
And in code-behind (suggest to use MVVM) property that will be responsible for holding _itemList:
public ObservableCollection<PmemCombItem> ItemsCollection
{
get
{
if (_itemList == null)
{
_itemList = new ObservableCollection<PmemCombItem>();
}
return _itemList;
}
}
UPDATE:
There is similar post which most probably will Answer your question: How do I update an ObservableCollection via a worker thread?

I found a way to do it. It is not really that great but it works.
YourList.ItemsSource = null;
// Update the List containing your elements (lets call it x)
YourList.ItemsSource = x;
this should refresh your ListView (it works for my UAP :) )

An alternative on Xopher's answer.
MyListView.ItemsSource = MyDataSource.ToList();
This refreshes the Listview because it's a other list.

Please check this answer:
Passing ListView Items to Commands using Prism Library
List view Items needs to notify about changes (done is setter)
public ObservableCollection<Model.Step> Steps
{
get { return _steps; }
set { SetProperty(ref _steps, value); }
}
and UpdateSourceTrigger need to be set in xaml
<Image Source="{Binding ImageData, UpdateSourceTrigger=PropertyChanged}" />

WPF iterate through datagrid

Using WPF C#.NET4.5 using visual studio 2012 ulti.
Old winforms code:
foreach (DataGridViewRow paretoRow in ParetoGrid.Rows)
{
if ((Convert.ToInt32(paretoRow.Cells["CurrentPareto"].Value) < (Convert.ToInt32(paretoRow.Cells["NewPareto"].Value))))
{
paretoRow.Cells["pNew"].Value = downArrow
}
}
As you can see each row I cycle through I check a specific cell, if true I then populate another cell. This was good old winforms code I used many times before...however.
Switching over to WPF was alot more different than i previously assumed.
DataGrid does not contain the Row property. Instead, I think you need to use:
DataGridRow paretoRow in paretogrid.Items
But im still at a loss on who to now get the cell.
So my question is, is there syntax changes to perform, if so where? Or as I'm beginning to believe datagrids in WPF operate with Objects more so than winforms thus not needing to use a propertie called "row", if this is the case what logic/syntax should i know use in this example?
Thanks for your patience guys, think when I go home for the bank holiday I'll do a bit of WPF digging to see how different it actually is.

People seem to be overcomplicating this, this worked for me:
foreach (System.Data.DataRowView dr in yourDataGrid.ItemsSource)
{
MessageBox.Show(dr[0].ToString());
}

I think first think you want to do is to get all rows of your DataGrid:
public IEnumerable<Microsoft.Windows.Controls.DataGridRow> GetDataGridRows(Microsoft.Windows.Controls.DataGrid grid)
{
var itemsSource = grid.ItemsSource as IEnumerable;
if (null == itemsSource) yield return null;
foreach (var item in itemsSource)
{
var row = grid.ItemContainerGenerator.ContainerFromItem(item) as Microsoft.Windows.Controls.DataGridRow;
if (null != row) yield return row;
}
}
and then iterate through your grid:
var rows = GetDataGridRows(nameofyordatagrid);
foreach (DataGridRow row in rows)
{
DataRowView rowView = (DataRowView)row.Item;
foreach (DataGridColumn column in nameofyordatagrid.Columns)
{
if (column.GetCellContent(row) is TextBlock)
{
TextBlock cellContent = column.GetCellContent(row) as TextBlock;
MessageBox.Show(cellContent.Text);
}
}

Yes, you are right. WPF DataGrid is built around better supporting the use of objects.
You could use a ViewModel similar to the following. Build them all into a collection and then set that collection as your ItemsSource. You would also need to use a ValueConverter if you want to display and image instead of a checkmark for pNew being true/false.
public class FooViewModel : INotifyPropertyChanged
{
private int currentPareto;
public int CurrentPareto
{
get
{
return currentPareto;
}
set
{
if (currentPareto == value)
return;
currentPareto = value;
OnPropertyChanged("CurrentPareto");
OnPropertyChanged("pNew");
}
}
private int newPareto;
public int NewPareto
{
get
{
return newPareto;
}
set
{
if (newPareto == value)
return;
newPareto = value;
OnPropertyChanged("NewPareto");
OnPropertyChanged("pNew");
}
}
public bool pNew
{
get
{
return CurrentPareto < NewPareto;
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Edit
To simplify it a little, you could use a base ViewModel class and use PropertyChanged weaving. The code would simplify to this:
public class FooViewModel : ViewModelBase
{
public int CurrentPareto { get; set; }
public int NewPareto { get; set; }
public bool pNew { get { return CurrentPareto < NewPareto; } }
}

I don't even understand why is it just so complicated to get rows and their values in a datagrid. It feels like hell finding how. The api even give funny funny event names which is not so direct to the point also. Why can't just people concentrate on the baseline and give what exactly is needed and not all sorts of different options with no use and sense at all. I mean to eat all you need is a spoon and fork right. Never even changed since 100,000 years ago. This is my code thanks to the guy who mentioned some people just try to over-complicate things and waste your time.
private void dtaResultGrid_DataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
{
ActivateTestDatagridAccess();
}
public async void ActivateTestDatagridAccess()
{
try
{
await Task.Delay(500);
foreach (System.Data.DataRowView dr in dtaResultGrid.ItemsSource)
{
for (int j = 0; j < dtaResultGrid.Columns.Count; j++)
{
Console.WriteLine(dr[j].ToString());
}
Console.Write(Environment.NewLine);
}
}
catch (Exception exrr)
{
Console.WriteLine(exrr.ToString());
}
}

The 'simplest' answer, from Charles, did it for me. But I used Items instead of ItemsSource.
Now, for people getting this error:
System.InvalidCastException
Unable to cast object of type 'MS.Internal.NamedObject' to type 'System.Data.DataRowView'.
What did it for me was disabling the DataGrid's property CanUserAddRows. This removes the placeholder line for a new line, thus removing the placeholder object (which is NOT a DataRowView, but something else). If you already have this disabled, then I don't know.
Since I wanted to loop through each element of each row, I added another foreach:
foreach (System.Data.DataRowView dr in nameofyourgrid.Items)
{
foreach (var item in dr.Row.ItemArray)
{
MessageBox.Show(item.ToString());
}
}

In WPF you go about it a lot more dynamic and ObjectOrientated. You can bind the Column "pNew" on a Property of the element you put in the DataGrid, which returns downarrow.
If the value changes you can raise the Event PropertyChanged (Interface INotifyPropertyChanged) and the bound Property will get reevaluated.
Also interesting for beginning with WPF is DataTemplate, ControlTemplate, Converter.
Converter changes the Property Value to a usable Value for WPF (e.g. BoolToVisibility) when the Property gets called.
DataTemplate and ControlTemplate can be used to alter the appearance of the Control.
There are several good Tutorials for WPF out there. I would also recommend to look into the MVVM-Pattern to use as a between layer of your Businessobject and your WPF-Control, especially to handle things like what you try to do here.

if you fill your datagridview rows using an instance of a class (like struct_class)
this would be the fastest way to have a foreach loop
foreach (struct_class row in dgv.Items)
{
MessageBox.Show(row.name);
}

Why can't you just use this property to get the number of rows and then use a For loop to iterate through?
dataGridView1.Rows.Count

wpf combobox selecteditem to null after onsourceinitialized

I have overrided the method OnSourceInitialized and I have one problem. After populating my combobox with source property from c# code I want automatically an item will appear selected in the combobox when a page is loaded (default value) but for some reason after onsourceinitialized method, the combobox selected item change to null.
EDIT
First of all, very good explanation thanks.
I'll try to explain more and I post some code following. I have made some modifications but without success. It continues not working.
My goal is to show a default value selected in the combobox when window is loaded and it is shown.
Initially, when user selects a option in menu application I do the following:
WinMain.xaml.cs:
namespace MyNamespace
{
public partial class WinMain : Window
{
<...>
private void mnuItemPreferences_Click(object sender, RoutedEventArgs e)
{
MyNamespace.Windows.EditPreferences editPrefWnd =
new MyNamesapece.Windows.EditPreferences();
//
// Modal window that I want to open with default values in comboboxes
//
editPrefWnd.ShowDialog();
}
<...>
} // end WinMain class
} // end namespace
EditPreferences.xaml.cs:
namespace MyNamespace.Windows
{
public partial class EditPreferences : Window
{
<...>
// My constructor
public EditPreferences()
{
//
// Handlers
//
Loaded += PreferencesWindow_Loaded;
Closing += PreferencesWindow_Closing;
InitializeComponent();
if (System.Environment.OSVersion.Version.Major < 6)
{
this.AllowsTransparency = true;
_bolAeroGlassEnabled = false;
}
else
{
_bolAeroGlassEnabled = true;
}
this.ShowInTaskbar = false;
} // end constructor
private void PreferencesWindow_Loaded(object sender,
System.Windows.RoutedEventArgs e)
{
if (this.ResizeMode != System.Windows.ResizeMode.NoResize)
{
//this work around is necessary when glass is enabled and the
//window style is None which removes the chrome because the
//resize mode MUST be set to CanResize or else glass won't display
this.MinHeight = this.ActualHeight;
this.MaxHeight = this.ActualHeight;
this.MinWidth = this.ActualWidth;
this.MaxWidth = this.ActualWidth;
}
//
// Populate comboboxes
//
cbLimHorasExtra.ItemsSource = Accessor.GetLimHorasExtraSorted();
cbFracHorasExtra.ItemsSource = Accessor.GetFracHorasExtraSorted();
//
// Fill controls with default values (see below)
//
FillControls();
//
// Install other handlers
//
rdoBtnOTE.Checked += this.rdoBtnOTE_Checked;
rdoBtnOTM.Checked += this.rdoBtnOTM_Checked;
chkboxRestrict.Checked += this.chkboxRestrict_Checked;
expAdditionalDetails.Collapsed +=
this.expAdditionalDetails_Collapsed;
expAdditionalDetails.Expanded += this.expAdditionalDetails_Expanded;
cbLimHorasExtra.SelectionChanged +=
this.cbLimHorasExtra_SelectionChanged;
cbFracHorasExtra.SelectionChanged +=
this.cbFracHorasExtra_SelectionChanged;
}
protected override void OnSourceInitialized(System.EventArgs e)
{
base.OnSourceInitialized(e);
if (_bolAeroGlassEnabled == false)
{
//no aero glass
this.borderCustomDialog.Background =
System.Windows.SystemColors.ActiveCaptionBrush;
this.tbCaption.Foreground =
System.Windows.SystemColors.ActiveCaptionTextBrush;
this.borderCustomDialog.CornerRadius =
new CornerRadius(10, 10, 0, 0);
this.borderCustomDialog.Padding =
new Thickness(4, 0, 4, 4);
this.borderCustomDialog.BorderThickness =
new Thickness(0, 0, 1, 1);
this.borderCustomDialog.BorderBrush =
System.Windows.Media.Brushes.Black;
}
else
{
//aero glass
if (VistaAeroAPI.ExtendGlassFrame(this,
new Thickness(0, 25, 0, 0)) == false)
{
//aero didn't work make window without glass
this.borderCustomDialog.Background =
System.Windows.SystemColors.ActiveCaptionBrush;
this.tbCaption.Foreground =
System.Windows.SystemColors.ActiveCaptionTextBrush;
this.borderCustomDialog.Padding =
new Thickness(4, 0, 4, 4);
this.borderCustomDialog.BorderThickness =
new Thickness(0, 0, 1, 1);
this.borderCustomDialog.BorderBrush =
System.Windows.Media.Brushes.Black;
_bolAeroGlassEnabled = false;
}
}
}
private void FillControls()
{
tblPreferencias tbl_pref = null;
//
// Obtain data (a record with fields)
// Accessor is a class where I define the methods to
// obtain data of different tables in my database
//
tbl_pref = Accessor.GetActualPreferencias();
//
// Only returns one register
//
if (tbl_pref != null)
{
rdoBtnOTE.IsChecked = (bool)tbl_pref.OTE;
rdoBtnOTM.IsChecked = (bool)tbl_pref.OTM;
chkboxRestrict.IsChecked =
(bool)tbl_pref.RestriccionHExtraTipoA;
// Here the value assigned is always in the range of the values
// which combo has been populated.
// With one 0 ... 8
// I debbugged it and works.
// selected value (no null) and text gets the correct value I
// want but after OnSourceInitialized method is executed I note
// that for some rease selected value property gets value null
cbLimHorasExtra.Text = tbl_pref.LimiteHorasExtra.ToString();
cbFracHorasExtra.Text =
tbl_pref.FraccionDeMinutosExtra.ToString();
}
}
<...>
} // end EditPreferences class
} // end namespace
EditPreferences.xaml (I put as example one of the comboboxes):
<Window x:Class="MyNamespace.Windows.EditPreferences"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="EditPreferences" Height="Auto" Width="500"
Background="{x:Null}"
SnapsToDevicePixels="True" SizeToContent="Height"
WindowStartupLocation="CenterScreen"
ResizeMode="NoResize"
WindowStyle="None"
Margin="0,0,0,0"
>
<...>
<ComboBox x:Name="cbLimHorasExtra"
DisplayMemberPath="LimHora"
SelectedValuePath="Id"
SelectedItem="{Binding Path=Id}"
VerticalAlignment="Center"
HorizontalContentAlignment="Right"
Width="50"/>
<...>
</Window>
Accessor.cs:
namespace GesHoras.Classes
{
class Accessor
{
<...>
// This method is used to populate the combobox with its values
// tblLimHorasExtra is a table in my SQL Database
// Its fields are:
//
// Id : int no null (numbers 1 ... 9)
// LimHora: int no null (numbers 0 ... 8)
//
public static System.Collections.IEnumerable GetLimHorasExtraSorted()
{
DataClassesBBDDDataContext dc = new
DataClassesBBDDDataContext();
return (from l in dc.GetTable<tblLimHorasExtra>()
orderby l.LimHora
select new { Id=l.Id, LimHora=l.LimHora });
}
// tblPreferencias is a table in my SQL Database
// Its fields are:
//
// Id : int no null
// Descripcion : varchar(50) no null
// OTE : bit no null
// OTM : bit no null
// LimiteHorasExtra : int no null
// FraccionDeMinutosExtra : int no null
// RestriccionHExtraTipoA : bit no null
//
public static tblPreferencias GetActualPreferencias()
{
DataClassesBBDDDataContext dc = new
DataClassesBBDDDataContext();
return (from actP in dc.GetTable<tblPreferencias>()
where (actP.Id == 3)
select actP).SingleOrDefault<tblPreferencias>();
}
<...>
} // end class
} // end namespace
The problem I see is that when method fillControls is executed all is ok, selectedvalue and text property for the combobox is correct (I have debbugged it and is correct) but after executing OnSourceInitialized method, selectedvalue property for the combobox gets null value.
Also I note that, when window opens, the comboboxes appear with the default values selected that I want but quickly I see that for some reason their values selected turns to empty in the comboboxes. It's like some event (I think after executing OnSourceMethod because I have debugged and see how it change to null) makes the selected default values that appears ok in the comboboxes turn to empty.
I have tested that comboboxes are populated correctly because once the window is shown I click in the comboboxes and I can see they are populated ok.
EDIT 2
Also I have forced selected index for combobox in fillControls method by doing:
cbLimHorasExtra.SelectedIndex = 1;
but without success...
The combobox is populated with values: 0 to 8 both included.

Cause
This appears to be the problem:
SelectedItem="{Binding Path=Id}"
If the "Id" property in the DataContext is not an item in the ItemsSource, SelectedItem will be set to null.
Timing
When InitializeComponent is called, it parses the XAML which sets the SelectedItem binding. If the DataContext is not set, then initially this will be null. Later when DataContext is set, the binding is re-evaluated. If Id is in the list at that point, the SelectedItem is set. Otherwise it is set to null.
Any binding that cannot be evaluated initially during InitializeComponent is scheduled using the dispatcher to be re-evaluated once all events have fired. Without details on how your DataContext is being set I can't give specifics, but my guess is that one of your binding is getting deferred so your {Binding Path=Id} binding is evaluated in a dispatcher callback.
A dispatcher callback is not an event - it is a prioritized work queue. If you have this kind of situations your choices are:
Change the bindings so they can be evaluated during initialization
Use a Dispather.BeginInvoke to schedule your own callback to execute after the Binding completes
Let the Binding take care of setting the SelectedItem rather than setting manually in code
Additional notes
Your use of SelectedValueSource looks suspicious. Your binding to SelectedItem seems to indicate that each item in the ItemsSource is an "Id", but your definition of SelectedValueSource seems to indicate that each item in the ItemsSource contains an "Id". It is rare to find a data structure where the structure itself is called "Id" by another structure, yet it itself has an "Id" field. Thus I suspect some confusion here. Without seeing your actual data structures I can't say more.
Your use of OnSourceInitialized also makes it appear you have a misunderstanding. The "Source" in the name of OnSourceInitialized refers to a "presentation source" such as a Win32 hWnd, not a source of data. The purpose of OnSourceInitialized is to interact at a low level with the Windows operating system, or to update your application based on where it is being presented. Your use seems completely unrelated to this. I would recommend you stay away from OnSourceInitialized. Generally the best time to initialize ComboBoxes and such is to just provide it in your view model and let data binding take care of it. As soon as the view model is available the data will be populated with no code required.

Set the SelectedIndex property at the end of your override, by the way, i can't seem to find OnSourceInitialised, only Initialised. But it should still work if you set it at the end of your code.
private void MyListBox_Initialized(object sender, EventArgs e)
{
// Run some code
if (MyListBox.Items.Count > 0)
{
MyListBox.SelectedIndex = 0;
}
}

I don't have a real answer to your question, but OnSourceInitialized seems to be too early in the initialization process.
Again, I have not tried your exact scenario, but many problems like this one are solved by calling FillControls (i.e. setting the selected item) in the Loaded event instead of earlier.

I have solved it!
The problem was in binding the SelectedItem property in EditPreferences.xaml:
<ComboBox x:Name="cbLimHorasExtra"
DisplayMemberPath="LimHora"
SelectedValuePath="Id"
SelectedItem="{Binding Path=Id}"
VerticalAlignment="Center"
HorizontalContentAlignment="Right"
Width="50"/>
The solution is to change to:
<ComboBox x:Name="cbLimHorasExtra"
DisplayMemberPath="LimHora"
SelectedValuePath="Id"
SelectedItem="Id"
VerticalAlignment="Center"
HorizontalContentAlignment="Right"
Width="50"/>