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WPF: Bind to SelectedItem of row in DataGrid

I'm very new to WPF. I'm trying to bind to a property a row in a DataGrid so that when the row's clicked the property is set. The ItemsSource that's bound to the DataGrid is an ObservableCollection of objects of type Field.
I've tried to bind to the SelectedItem attribute on the DataGrid, but the property is not being called. I'm using almost identical code to bind to the SelectedItem of a ComboBox and this is working fine. Is there a difference that I don't know about?
<ComboBox ItemsSource="{Binding RecordTypes}" SelectedItem="{Binding SelectedRecordType}" ...
<DataGrid ItemsSource="{Binding Fields}" SelectedItem="{Binding SelectedField}" ...
In my ViewModel:
private Field SelectedField
{
get
{
return _selectedField;
}
set
{
_selectedField = value;
}
}
(I will use auto properties later, it's just currently set up like this so that I could break when the property was set).
I'm not sure if it makes a difference, but the DataGrid is composed of 2 DataGridTextColumns and a DataGridTemplateColumn, which contains a checkbox.
Does anyone have any ideas? I'd really appreciate any suggestions.
To confirm, the reason that I want to listen to the click of a row is so that I can have the checkbox be checked whenever a row is clicked. If there's a better solution for this then please let me know.

You need to make it a two-way binding:
SelectedItem="{Binding SelectedField,Mode=TwoWay}"
That propagates changes in the view (user selects an item, SelectedItem changes) back to the viewmodel ("SelectedField" property).
Also, as #KevinDiTraglia pointed out, you need to make sure that the viewmodel property SelectedField is public, not private, otherwise the binding will not be able to access the getter/setter.

ComboBox ItemsSource binding not updated after value selected

I have a ComboBox in WPF binding its ItemsSource Property to a Property returning an IEnumerable of String. The binding is just one-way. The class that contains the data for the ComboBox implements INotifyPropertyChanged Interface and calls the OnPropertyChanged(..) as soon as the Property gets updated. When I leave the ComboBox untouched the changes are correctly propagated. But as soon as the ComboBox is expanded once or a value is selected the changes in the ItemsSource Collection are no longer updated. What may be the reason for this behaviour?
Heres the XAML
<ComboBox Name="cmbSourceNames"
Grid.Row="0"
SelectedItem="{Binding Path=CurrentSource, UpdateSourceTrigger=PropertyChanged}"
ItemsSource="{Binding Path=SourceAddresses, NotifyOnSourceUpdated=True}"/>
The DataContext is set in the code behind:
this.cmbSourceNames.DataContext = this._dpa;
And this one is the Method that triggers the change of the Property. The Method for adding the Packet is delegated to the Current Dispatcher with BeginInvoke.
private void DispatcherAddDataPacket(DataPacket dp)
{
ObservableCollection<DataPacket> dpList;
this._dpkts.TryGetValue(dp.SourceAddress, out dpList);
if (dpList == null)
{
dpList = new ObservableCollection<DataPacket>();
dpList.Add(dp);
this._dpkts.Add(dp.SourceAddress, dpList);
OnPropertyChanged("SourceAddresses");
}
else
{
dpList.Add(dp);
}
}
The Property is giving back the Keys of the Dictionary as IEnumerable.

Finally I implemented the Binding Property using an ObservableCollection tracking the keys when a new Packet gets added (so every key to the Dictionary has an equivalent in this ObservableCollection). I think it's not really a satisfying solution (because you have to keep track of both Collections independently) but it works like this.

Two-way binding combobox to enum

I have a View that is linked to my ViewModel using a DataTemplate, like this
<DataTemplate DataType="{x:Type ViewModels:ViewModel}">
<Views:View />
</DataTemplate>
The ViewModel holds a property ProcessOption that is of type MyEnum?, where MyEnum is a custom enumeration that has let's say 3 values: Single, Multiple and All. I am trying to bind a combobox to this property, so the approach I am following is:
ViewModel has a property of List<string> that is
public List<string> Options
{
get
{
return Enum.GetNames(typeof(MyEnum)).ToList();
}
}
to which I bind the ItemsSource property of the Combobox. Then, in addition to the ProcessOption property, the ViewModel also has an OptionName property (of string), which is intended to hold the selected option's name. The ViewModel implements INotifyPropertyChanged and both properties raise the PropertyChanged event in their setters. The binding I am using then is:
<ComboBox ItemsSource="{Binding Options}"
SelectedItem="{Binding OptionName}"
SelectedValue="{Binding ProcessOption}"/>
This works fine up to this point. Initially the combobox is empty and both properties are null, and when the user selects an option this is propagated to the ViewModel as it should.
The problem appears when I load the data from a Database, and I want to load the controls with initial values. In this case, in the ViewModel's constructor I have this:
this.ProcessOption = objectFromDB.ProcessOption // this is the value restored from DB, let's say it is MyEnum.Multiple
this.OptionName = Options.First(x => x.Equals(Enum.GetName(typeof(MyEnum), objectFromDB.ProcessOption)));
The problem is, although the above sets the two properties to their correct values, they are later set to null from the Combobox binding, so the initial values are not kept. I have also tried to do something like if (value == null) { return; } in the properties' setters, in which case they have the correct values after the View loads, however the Combobox still does not display the correct option, it is empty.
I should also note that I've also tried setting IsSynchronisedWithCurrentItem and it doesn't make any difference, apart from the fact that the first element is displayed instead of the combobox being empty.
Can anyone help with this binding? Any help will be very much appreciated, this is driving me crazy!

<ComboBox ItemsSource="{Binding Options}"
SelectedItem="{Binding OptionName}"
SelectedValue="{Binding ProcessOption}"/>
Your binding doesn't look like it should work at all -- you don't have TwoWay binding set up, and I think SelectedItem and SelectedValue is an either/or proposition.
I suggest that you get rid of OptionName and just bind SelectedItem to ProcessOption (TwoWay) with an IValueConverter that will convert to/from string.

Changing Data Context for Data Template clears Combo Box selection

I have a TreeView that permits the user to select different items. The display for each item is determined using Data Templates with the DataType set to the appropriate ViewModel type. The DataContext is automatically set based on the selected item in the tree view to the appropriate ViewModel.
Here's the problem:
One of the DataTemplates has a ComboBox bound to an ObservableCollection to get the list of items and a property to get/set the SelectedValue in the ViewModel.
When I select one item of this type, and then select another item of the same type, the ComboBox displays blank instead of the correct selected item. It appears that the Combo Box is setting the SelectedValue property to NULL immediately after the transition to the new item, and then never updating.
<ComboBox Margin="1,0"
ItemsSource="{Binding ItemsToSelect}"
SelectedValue="{Binding SelectedValue}"
SelectedValuePath="ValuePath" DisplayMemberPath="DisplayPath"
IsEnabled="{Binding CanSelectItem}">
</ComboBox>
The really strange part is if I select an item of a different type between selecting items of the same type, it always displays correctly.
I've tried ignoring the NULL value in the SelectedValue setter, and that didn't work regardless of whether I also raised the PropertyChanged event or not.
private MyObject selectedValue;
public MyObject SelectedValue
{
get
{
return selectedValue;
}
set
{
if (value != null)
{
this.selectedValue = value;
}
this.OnPropertyChanged("SelectedValue");
}
}
Looking at the similar questions while writing this lead me to an interesting attribute that I hadn't found yet - IsSynchronizedWithCurrentItem from this question. At first, I thought this solved the problem, but alas it just changes the behavior somewhat.
With this attribute set to True, the combo doesn't entirely clear its selection, but instead just marks the first item as selected. So, instead of being set to NULL, now the SelectedValue property is being set to the first item in the list.
Anyone have any ideas for a solution?

If I understand your problem correctly, a couple of things are going on here.
First you do not have Mode=TwoWay, UpdateSourceTrigger=PropertyChanged} set in your bindings.
Second, the property binding will only update if there is a change in the value itself.
Check this out Data Binding

I figured out a work around, but it isn't quite what I wanted.
I changed the binding to use SelectedItem instead of SelectedValue, and the issue doesn't occur.
I got the idea from this question.
So I changed
SelectedValue="{Binding SelectedValue}"
To (and renamed my ViewModel Property):
SelectedItem="{Binding SelectedItem}"
After updating the uses of this property in the ViewModel, everything worked.

Silverlight Combobox loses visual value, but keeps selected value when the page it's on is hidden and reshown

I'm using a Silverlight 4.0 project that utilizes MVVM and we have a combobox that resides on a view and has its values and selected value bound to an observable collection of Organizations and a SelectedOrganization respectively (both values exist on the viewmodel). With our project the page that this control is on can be hidden or shown. The first load everything looks great but when you go to a different control (hide the tab with the control and then go back to it) the value that is currently selected in the combo box looks like it's blank, but when I debug, the selected value is still there.
The visual tree is getting recreated, but I have no idea why the combobox loses the text that should be in the box when the parent page is hidden and then re-shown. All other controls on the page behave correctly (autocompletetextbox, textblocks, textboxes, all of which have data bound to the viewmodel the same way).
Here's how the combobox is declared:
<ComboBox
SelectedItem="{Binding SelectedOrganization, Mode=TwoWay}"
ItemsSource="{Binding Organizations}"
DisplayMemberPath="Name"
Margin="5,0"
MinWidth="100" />
the Class for the organization is here:
[DataContract]
public class Organization
{
[DataMember]
public Guid OrganizationID { get; set; }
[DataMember]
public string Name { get; set; }
}
and the viewmodel has the following code for the bindings:
public Organization SelectedOrganization
{
get { return (Organization)GetValue("SelectedOrganization"); }
set
{
SetValue("SelectedOrganization", value);
}
}
public ObservableCollection<Organization> Organizations
{
get { return (ObservableCollection<Organization>)GetValue("Organizations"); }
set { SetValue("Organizations", value); }
}
What do I need to do to keep the selected value when I switch parent pages?

The problem is that I declared the ItemsSource AFTER the SelectedItem. Apparently this is a bug in Silverlight 3 and 4. The answer was discussed here Silverlight Combobox and SelectedItem.

Just a quick note on yet a SL3 bug.
I haven't reproduced this bug in a clean environment (since I'm getting quite tiered of reproducing SL ComboBox bug's...), but I experienced an issue with roughly this setup:
ItemsSource binds to property of type List on Object X.
SelectedItem binds to property of type String on Object X.
Object X implements INotifyPropertyChanged.
SelectedItem is set after ItemsSource in XAML code as the above post instructs.
ItemsSource is set to TwoWay BindingMode.
Behaviour: When the user TAB's from a textbox into the combobox, the combobox value is 'blanked', while the ViewModel maintains its value. The value is displayed again correctly when the user TAB's out of the ComboBox. Please note that the value is not blanked, if the combobox is merely clicked, or if it tabbed to from another combobox.
Solution: When stepping through the code with a debug'er it seems that SelectedItem is returned before ItemsSource, even though ItemsSource is declared before SelectedItem in the XAML code.
The solution was to change the ItemsSource from TwoWay BindingMode to OneWay BindingMode.
Probably this prevents some events from being fiered behind the scenes.
Br. Morten

Could be helpful if adding to previous post, I noticed that my selectedItem binding property must contain a conditional that avoid assing null value, because combobox control still wants to reset value once the control is hidden by scroll or whatever.
i.e. :
public string Month{
get {return _month;}
set {
if (value==null)
return;
_month = value;
}
}

Use this
<ScrollViewer Grid.Row="6" Grid.ColumnSpan="4" Height="190">
<sdk:DataGrid Name="datagridInvestigation"
AutoGenerateColumns="False" Width="650"
MinHeight="180" >
</sdk:DataGrid>
</ScrollViewer>
instead of
<sdk:DataGrid Name="datagridInvestigation"
AutoGenerateColumns="False" Width="650"
Height="180" ScrollViewer.HorizontalScrollBarVisibility="Auto" >