Incomplete display of items in combobox wpf c# - combobox

I'm using wpf c# and Entity Framework
I have a DataGrid on that show data from database
when users click on datagrid that row will show items in ComboBox (Load on of columns in combobox)
but problem is combobox doesn't show Normal list
Code CS Behind :
DENAF1399Entities dbms = new DENAF1399Entities();
private void Window_Loaded(object sender, RoutedEventArgs e)
{
var qre = dbms.Database.SqlQuery<Q_View>("SELECT * FROM Q_View");
datagrid1.ItemsSource = qre.ToList();
}
private void datagrid1_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
Q_View QVkala = datagrid1.SelectedItem as Q_View;
if (QVkala != null)
{
combobox1.ItemsSource = QVkala.NAMES;
}
}
I tried
-Change Fonts of combobox
-use new combobox
but didn't work
please help me

Edit during formation: It just became obvious to me what's going on. Q_View.NAMES is a string, and by setting combobox1.ItemsSource to that property, it's identifying the individual items as characters in the string (as string is an IEnumerable<char>).
If what you want in the combo box is what's in each of the columns of the selected item, then the way to do that is like this:
private void datagrid1_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
Q_View QVkala = datagrid1.SelectedItem as Q_View;
if (QVkala != null)
{
object[] items = { QVkala.CODE, QVkala.NAME, QVkala.NAMES, QVkala.TOZIH } //etc whatever properties you want to project into this
combobox1.ItemsSource = items;
}
}
ORIGINAL WORK ON AN ANSWER
At first glance it looks like your data is transposed, but altogether it looks like you aren't using WPF or Entity Framework like you really could be using them. WPF was made for MVVM design and Entity Framework was made for treating tables like collections of objects. Not knowing much else about your application, here's how I'd get started:
First, I'd move basically everything except what's auto-generated out of MainWindow.xaml.cs, and start a new separate class. (Note: may have compiler errors as this is completely off the cuff)
public class MainWindowViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged; //MainWindow.xaml will hook into this
public ObservableCollection<Q_View> Q_Views { get; private set; }
private Q_View selectedQView;
public Q_View SelectedQView
{
get => selectedQView;
set
{
if(value != selectedQView)
{
selectedQView = value;
PropertyChanged?.Invoke("SelectedQView");
}
}
}
}
And then in MainWindow.xaml.cs, the only change from what's generated would be the constructor (there's another way to do this even without changing the code-behind but I'll not get into it here since I'm not as xaml-adept as I am with C#)
public class MainWindow : Window
{
public MainWindow()
{
DataContext = new MainWindowViewModel();
InitializeComponent(); //that's auto-generated
}
}
And finally, the xaml for your DataGrid. Edit it like this:
<DataGrid Name="QViewDataGrid" AutoGenerateColumns="False" ItemsSource="{Binding Q_Views}" SelectedItem="{Binding SelectedQView}">
<DataGrid.Columns>
<DataGridTextColumn Header="CODE" Binding="{Binding Path="CODE"}"> //and so forth with more columns
</DataGrid.Columns>
</DataGrid>
ComboBox will have a similar syntax for binding an ItemsSource and SelectedItem. Doing this enables you to avoid having event handlers and dealing with boiler plate for updating so many things.

Related

Problems using inheritance with drag and drop in WPF

I have a usercontrol that I want to implement a drag and drop interface on, here are the vital parts of the implementation, and this works fine:
XML-file to the usercontrol to be draggable:
<UserControl
...default xmlns...
MouseLeftButtonDown="Control_MouseLeftButtonDown">
...GUI-ELEMENTS in the control...
</UserControl>
Code behind:
public partial class DragableControl : UserControl
{
private void Control_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
DragDrop.DoDragDrop(this, this, DragDropEffects.Move);
}
}
XML-file to the usercontrol which will be able to accept a drag and drop operation:
<Usercontrol
...default xmlns...>
<Grid AllowDrop="True" Drop="Grid_Drop">
... GUI elements in the grid....
</Grid>
</Usercontrol>
Code behind:
public partial class DropClass: UserControl
{
private void Grid_Drop(object sender, DragEventArgs e)
{
var control = (DragableControl)e.Data.GetData(typeof(DragableControl));
if(control != null)
{
//do something
}
}
}
To be able to create different usercontrols which have drag and drop functionality, I creates a base class, BaseDragableUserControl, which at the moment contains nothing, but inherits from usercontrol.
Code:
public class BaseDragableUserControl: UserControl
{
}
I change my code (both xaml and code):
public partial class DragableControl : UserControl
I also changes the class for receiving to this:
public partial class DropClass: UserControl
{
private void Grid_Drop(object sender, DragEventArgs e)
{
var control =(BaseDragableUserControl)e.Data.GetData(typeof(BaseDragableUserControl));
if(control != null)
{
//do something
}
}
}
But the control variable is always Null. I guess that the getdata in the DragEventsArgs does not like inheritance. Is there a way to achieve this? To make it possible to use a base class for a drag and drop class?
Instead of passing this when you initiate the drag/drop, create one of the standard containers for that purpose. Specifically:
DragDrop.DoDragDrop(this, new DataObject("myFormat", this), DragDropEffects.Move);
and then now you know to expect a specific kind of data:
var control =(BaseDragableUserControl)e.Data.GetData("myFormat");

WPF ComboBox SelectedItem Set to Null on TabControl Switch

I've got a simple problem in my WPF application which has me banging my head on the table. I have a TabControl, where every TabItem is a View generated for a ViewModel using a DataTemplate similar to this:
<DataTemplate DataType="{x:Type vm:FooViewModel}">
<vw:FooView/>
</DataTemplate>
FooView contains a ComboBox:
<ComboBox ItemsSource="{Binding Path=BarList}" DisplayMemberPath="Name" SelectedItem="{Binding Path=SelectedBar}"/>
and FooViewModel contains a simple Property: public Bar SelectedBar { get; set; }. My problem is that when I set the value for my ComboBox, change to another tab, then change back, the ComboBox is empty again. If I set a breakpoint on the setter for my property, I see that the property is assigned to null when I switch to another tab.
From what I understand, when a tab is switched, it is removed from the VisualTree - but why is it setting my ViewModel's property to null? This is making it very difficult for me to hold persistent state, and checking value != null does not seem like the right solution. Can anyone shed some like on this situation?
Edit: The call stack at the setter breakpoint only shows [External Code] - no hints there.
We just ran into the same problem. We found a blog entry describing the problem. It looks like it is a BUG in WPF and there is a workaround:
Specify the SelectedItem binding before the ItemsSource binding and the problem should be gone.
blog article
TLDR;
Change:
<ComboBox ItemsSource="{Binding Countries, Mode=OneWay}"
SelectedItem="{Binding SelectedCountry}"
DisplayMemberPath="Name" >
</ComboBox>
To:
<ComboBox SelectedItem="{Binding SelectedCountry}"
ItemsSource="{Binding Countries, Mode=OneWay}"
DisplayMemberPath="Name" >
</ComboBox>
My app is using avalondock & prims and had that exact problem. I has same thought with BSG, when we switched tab or document content in MVVM app, the controls as listview+box, combobox is removed from VisualTree. I bugged and saw most data of them was reset to null such as itemssource, selecteditem, .. but selectedboxitem was still hold current value.
A approach is in model, check its value is null then return like this:
private Employee _selectedEmployee;
public Employee SelectedEmployee
{
get { return _selectedEmployee; }
set
{
if (_selectedEmployee == value ||
IsAdding ||
(value == null && Employees.Count > 0))
{
return;
}
_selectedEmployee = value;
OnPropertyChanged(() => SelectedEmployee);
}
But this approach can only solve quite good in first binding level. i mean,
how we go if want to bind SelectedEmployee.Office to combobox, do same is not good
if check in propertyChanged event of SelectedEmployee model.
Basically, we dont want its value is reset null, keep its pre-value. I found a new solution
consistently. By using attached property, i created KeepSelection a-Pro, bool type, for Selector controls, thus supply all its inherited suck as listview, combobox...
public class SelectorBehavior
{
public static bool GetKeepSelection(DependencyObject obj)
{
return (bool)obj.GetValue(KeepSelectionProperty);
}
public static void SetKeepSelection(DependencyObject obj, bool value)
{
obj.SetValue(KeepSelectionProperty, value);
}
// Using a DependencyProperty as the backing store for KeepSelection. This enables animation, styling, binding, etc...
public static readonly DependencyProperty KeepSelectionProperty =
DependencyProperty.RegisterAttached("KeepSelection", typeof(bool), typeof(SelectorBehavior),
new UIPropertyMetadata(false, new PropertyChangedCallback(onKeepSelectionChanged)));
static void onKeepSelectionChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var selector = d as Selector;
var value = (bool)e.NewValue;
if (value)
{
selector.SelectionChanged += selector_SelectionChanged;
}
else
{
selector.SelectionChanged -= selector_SelectionChanged;
}
}
static void selector_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
var selector = sender as Selector;
if (e.RemovedItems.Count > 0)
{
var deselectedItem = e.RemovedItems[0];
if (selector.SelectedItem == null)
{
selector.SelectedItem = deselectedItem;
e.Handled = true;
}
}
}
}
Final, i use this approach simply in xaml:
<ComboBox lsControl:SelectorBehavior.KeepSelection="true"
ItemsSource="{Binding Offices}"
SelectedItem="{Binding SelectedEmployee.Office}"
SelectedValuePath="Id"
DisplayMemberPath="Name"></ComboBox>
But, selecteditem will never null if selector's itemssource has items. It may affect
some special context.
Hope that helps.
Happy conding! :D
longsam
I had this same problem when scrolling through a virtualizing DataGrid that contains ComboBoxes. Using IsSynchronizedWithCurrentItem did not work, nor did changing the order of the SelectedItem and ItemsSource bindings. But here is an ugly hack that seems to work:
First, give your ComboBox an x:Name. This should be in the XAML for a control with a single ComboBox. For example:
<ComboBox x:Name="mComboBox" SelectedItem="{Binding SelectedTarget.WritableData, Mode=TwoWay}">
Then add these two event handlers in your codebehind:
using System.Windows.Controls;
using System.Windows;
namespace SATS.FileParsing.UserLogic
{
public partial class VariableTargetSelector : UserControl
{
public VariableTargetSelector()
{
InitializeComponent();
mComboBox.DataContextChanged += mComboBox_DataContextChanged;
mComboBox.SelectionChanged += mComboBox_SelectionChanged;
}
/// <summary>
/// Without this, if you grab the scrollbar and frantically scroll around, some ComboBoxes get their SelectedItem set to null.
/// Don't ask me why.
/// </summary>
void mComboBox_DataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
{
mComboBox.GetBindingExpression(ComboBox.SelectedItemProperty).UpdateTarget();
}
/// <summary>
/// Without this, picking a new item in the dropdown does not update IVariablePair.SelectedTarget.WritableData.
/// Don't ask me why.
/// </summary>
void mComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
mComboBox.GetBindingExpression(ComboBox.SelectedItemProperty).UpdateSource();
}
}
}
Generally, I use SelectedValue instead of SelectedItem. If I need the object associated with the SelectedValue then I add a lookup field containing this to the target object (as I use T4 templates to gen my viewmodels this tends to be in a partial class). If you use a nullable property to store the SelectedValue then you will experience the problem described above, however if binding the SelectedValue to a non-nullable value (such as an int) then the WPF binding engine will discard the null value as being inappropriate for the target.
Edit:
Below stuff works (I hope...); I developed it because I followed the SelectedItems route described on the MVVM Lite page. However - why do I want to rely on SelectedItems? Adding an IsSelected property to my Items (as shown here) automatically preserves selected items (short of the mentioned cavet in above link). In the end, much easier!
Inital Post:
ok - that was a piece of work; I've a multi-column ListView with SelectionMode="Extension", which makes the whole thing fairly complex. My starting point is invoking tabItems from workspaces similar as describe here.
I made sure that in my ViewModel, I know when a tab item (workspace) is active. (This is a bit similar to here) - of course, somebody needs initalize SelectedWorkspace first.
private Int32 _selectedWorkspace;
public Int32 SelectedWorkspace {
get { return _selectedWorkspace; }
set {
_selectedWorkspace = value;
base.OnPropertyChanged("SelectedWorkspace");
}
}
protected Int32 _thisWorkspaceIdx = -1;
protected Int32 _oldSelectedWorkspace = -1;
public void OnSelectedWorkspaceChanged(object sender, PropertyChangedEventArgs e) {
if (e.PropertyName == "SelectedWorkspace") {
if (_oldSelectedWorkspace >= 0) {
Workspaces[_oldSelectedWorkpace].OnIsActivatedChanged(false);
}
Workspaces[SelectedWorkspace].OnIsActivatedChanged(true);
_oldSelectedWorkspace = SelectedWorkspace;
}
}
protected bool _isActive = false;
protected virtual void OnIsActivatedChanged(bool isActive) {
_isActive = isActive;
}
This allowed me to update the ViewModel selected items only if the tab item (workspace) was actually active. Hence, my ViewModel selected items list is preserved even as the tab item clears the ListView.SelectedItems. In the ViewModel:
if (_isActive) {
// ... update ViewModel selected items, referred below as vm.selectedItems
}
Last, when the tabItem got re-enabled, I hooked up to the 'Loaded' event and restored the SelectedItems. This is done in the code-behind of the View. (Note that whilst my ListView has multiple columns, one serves as a key, the others are for information only. the ViewModel selectedItems list only keeps the key. Else, the comparison below would be more complex):
private void myList_Loaded(object sender, RoutedEventArgs e) {
myViewModel vm = DataContext as myViewModel;
if (vm.selectedItems.Count > 0) {
foreach (string myKey in vm.selectedItems) {
foreach (var item in myList.Items) {
MyViewModel.MyItem i = item as MyViewModel.MyItem;
if (i.Key == myKey) {
myList.SelectedItems.Add(item);
}
}
}
}
}
if you suing async selection in WPF then remove it IsSynchronizedWithCurrentItem="True" from for the ComboBox, please refer to the document about IsSynchronizedWithCurrentItem:
<ComboBox
Name="tmpName"
Grid.Row="10"
Width="250"
Text="Best Match Position List"
HorizontalAlignment="Left"
Margin="14,0,0,0"
SelectedItem="{Binding Path=selectedSurceList,Mode=TwoWay}"
ItemsSource="{Binding Path=abcList}"
DisplayMemberPath="Name"
SelectedValuePath="Code"
IsEnabled="{Binding ElementName=UserBestMatchYesRadioBtn,Path=IsChecked}">
</ComboBox>
also takecare the binding
first use SelectedItem
then ItemsSource
ref:
http://social.msdn.microsoft.com/Forums/vstudio/en-US/fb8a8ad2-83c1-43df-b3c9-61353979d3d7/comboboxselectedvalue-is-lost-when-itemssource-is-updated?forum=wpf
http://social.msdn.microsoft.com/Forums/en-US/c9e62ad7-926e-4612-8b0c-cc75fbd160fd/bug-in-wpf-combobox-data-binding
I solve my problem using the above
I once had a similar problem. It seems that the combobox looses the selected item in VisibilityChanged event. Workarround is to clear the binding before this occurs, and reset it when coming back. You can also try to set the Binding to Mode=TwoWay
Hope that this helps
Jan
I had the same problem and solved it with the following method attached to the Combobox DataContextChanged-Event:
private void myCombobox_DataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
{
if (sender is FrameworkElement && e.NewValue == null)
((FrameworkElement)sender).DataContext = e.OldValue;
}
So everytime you want to remove the datacontext from the combobox, the old datacontext will be set again.
Everytime you change the active Tab of your TabControl, the Combobox will removed from your VisualTree and added if you go back to the one with your combobox. If the combo box is removed from the VisualTree, also the DataContext is set to null.
Or you use a class, which have implemented such feature:
public class MyCombobox : ComboBox
{
public MyCombobox()
{
this.DataContextChanged += MyCombobox_DataContextChanged;
}
void MyCombobox_DataContextChanged(object sender, System.Windows.DependencyPropertyChangedEventArgs e)
{
if (sender is FrameworkElement && e.NewValue == null)
((FrameworkElement)sender).DataContext = e.OldValue;
}
public void SetDataContextExplicit(object dataContext)
{
lock(this.DataContext)
{
this.DataContextChanged -= MyCombobox_DataContextChanged;
this.DataContext = dataContext;
this.DataContextChanged += MyCombobox_DataContextChanged;
}
}
}
I think the problem may be that you arent telling the Combo box when to bind back to the source. Try this:
<ComboBox ItemsSource="{Binding Path=BarList}" DisplayMemberPath="Name" SelectedItem="{Binding Path=SelectedBar, UpdateSourceTrigger=PropertyChanged}"/
You can use the MVVM framework Catel and the catel:TabControl element there this problem is already solved.
Just don't allow your ViewModel's property to be changed if value becomes null.
public Bar SelectedBar
{
get { return barSelected; }
set { if (value != null) SetProperty(ref barSelected, value); }
}
That's it.

Loading and binding a serialized view model to a WPF window?

I'm writing a one-window UI for a simple ETL tool. The UI consists of the window, the code behind for the window, a view model for the window, and the business logic. I wanted to provide functionality to the users to save the state of the UI because the content of about 10-12 text boxes will be reused between sessions, but are specific to the user. I figured I could serialize the view model, which contains all the data from the textboxes, and this works fine, but I'm having trouble loading the information in the serialized XML file back into the text boxes.
Constructor of window:
public ETLWindow()
{
InitializeComponent();
_viewModel = new ViewModel();
this.DataContext = _viewModel;
_viewModel.State = Constants.STATE_IDLE;
Loaded += new RoutedEventHandler(MainWindow_Loaded);
}
XAML:
<TextBox x:Name="targetDirectory"
IsReadOnly="true"
Text="{Binding TargetDatabaseDirectory, UpdateSourceTrigger=PropertyChanged}"/>
ViewModel corresponding property:
private string _targetDatabaseDirectory;
[XmlElement()]
public string TargetDatabaseDirectory
{
get { return _targetDatabaseDirectory; }
set { _targetDatabaseDirectory = value; OnPropertyChanged(DataUtilities.General.Utilities.GetPropertyName(() => new ViewModel().TargetDatabaseDirectory)); }
Load event in code behind:
private void loadState_Click(object sender, RoutedEventArgs e)
{
string statePath = this.getFilePath();
_viewModel = ViewModel.LoadModel(statePath);
}
As you can guess, the LoadModel method deserializes the serialized file on the user's drive.
I couldn't find much on the web regarding this issue. I know this probably has something to do with my bindings. Is there some way to refresh on the bindings on the XAML after I deserialize the view model? Or perhaps refresh all properties on the view model? Or am I completely insane thinking any of this could be done?
Thanks.
Assuming that your loadState_Click event is on the Window code behind you could try this.
private void loadState_Click(object sender, RoutedEventArgs e)
{
string statePath = this.getFilePath();
this.DataContext = ViewModel.LoadModel(statePath);
}

Silverlight get selected row data in DataGrid

In my Silverlight application I have defined a datagrid with an template column containing a radio button as follows:
XAML:
<data:DataGrid x:Name="Grid1" Margin="8">
<data:DataGrid.Columns>
<data:DataGridTemplateColumn Header="RadioButtons">
<data:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<RadioButton x:Name="rdbIndataGrid" IsChecked="false" GroupName="myGroup" />
</DataTemplate>
</data:DataGridTemplateColumn.CellTemplate>
</data:DataGridTemplateColumn>
</data:DataGrid.Columns>
</data:DataGrid>
C#
public MainPage()
{
// Required to initialize variables
InitializeComponent();
string data = "1,2,3,4,5,6,7,8,9";
Grid1.ItemsSource = data.Split(',');
}
When a button is clicked I want to be able to:
a) Find out which radio button was selected.
b) Get the data from one of the cells in the grid which corresponds to the selected radio button.
Is there an easy way to do this? There doesnt seem to be a rows collection on the grid. Or do I have to bind it to a datasource and then check the data source?
Many thanks.
The way I'd prefer to do this would be to bind IsChecked to a property of objects assigned to the ItemsSource. But here I'll show you the hard way to do it
(Edit: Actually the following is over complicated for this scenario but I'll leave it here for now, see edits after)
First you need one of my VisualTreeEnumeration extension methods:-
public static class VisualTreeEnumeration
{
public static IEnumerable<DependencyObject> Ancestors(this DependencyObject root)
{
DependencyObject current = VisualTreeHelper.GetParent(root);
while (current != null)
{
yield return current;
current = VisualTreeHelper.GetParent(current);
}
}
}
Now in my testing I've just added a ListBox with the name lstOutput to my Xaml. Now add the following couple of event handlers to you UserControl :-
private void rdbIndataGrid_Checked(object sender, RoutedEventArgs e)
{
DataGridRow row = ((DependencyObject)sender).Ancestors().OfType<DataGridRow>().FirstOrDefault();
if (row != null)
lstOutput.Items.Add(String.Format("Checked: {0}", row.DataContext));
}
private void rdbIndataGrid_Unchecked(object sender, RoutedEventArgs e)
{
DataGridRow row = ((DependencyObject)sender).Ancestors().OfType<DataGridRow>().FirstOrDefault();
if (row != null)
lstOutput.Items.Add(String.Format("Unchecked: {0}", row.DataContext));
}
and finally tweak the Radio button Xaml like so:-
<RadioButton x:Name="rdbIndataGrid" IsChecked="false" GroupName="myGroup"
Checked="rdbIndataGrid_Checked" Unchecked="rdbIndataGrid_Unchecked" />
(One of the neat things about Xaml wiring up events is that it works even when the elements are part of a Template).
You'll note that in the event handlers I'm walking up the visual tree from the sending RadioButton to find the containing DataGridRow. The DataGridRow is the object that its DataContext set to the object being rendered by that row. In your own code you could cast the data context value to the correct type and from there access other data about the row.
Edit
Actually in most ordinary cases you don't need to hunt down the owning DataGridRow object accessing the DataContext property of the sending RadioButton is sufficient:-
private void rdbIndataGrid_Checked(object sender, RoutedEventArgs e)
{
object myData = ((FrameworkElement)sender).DataContext;
if (myData != null)
lstOutput.Items.Add(String.Format("Checked: {0}", myData));
}
private void rdbIndataGrid_Unchecked(object sender, RoutedEventArgs e)
{
object myData = ((FrameworkElement)sender).DataContext;
if (myData != null)
lstOutput.Items.Add(String.Format("Unchecked: {0}", myData));
}
Hence you can dispense with the Ancestors extension method. However in more complex cases where the DataContext have been changed the original "over-complicated" approach may be needed.

How to bind DataGridColumn.Visibility?

I have an issue similar to the following post:
Silverlight DataGridTextColumn Binding Visibility
I need to have a Column within a Silverlight DataGrid be visibile/collapsed based on a value within a ViewModel. To accomplish this I am attempting to Bind the Visibility property to a ViewModel. However I soon discovered that the Visibility property is not a DependencyProperty, therefore it cannot be bound.
To solve this, I attempted to subclass my own DataGridTextColumn. With this new class, I have created a DependencyProperty, which ultimately pushes the changes to the DataGridTextColumn.Visibility property. This works well, if I don't databind. The moment I databind to my new property, it fails, with a AG_E_PARSER_BAD_PROPERTY_VALUE exception.
public class MyDataGridTextColumn : DataGridTextColumn
{
#region public Visibility MyVisibility
public static readonly DependencyProperty MyVisibilityProperty =
DependencyProperty.Register("MyVisibility", typeof(Visibility), typeof(MyDataGridTextColumn), new PropertyMetadata(Visibility.Visible, OnMyVisibilityPropertyChanged));
private static void OnMyVisibilityPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var #this = d as MyDataGridTextColumn;
if (#this != null)
{
#this.OnMyVisibilityChanged((Visibility)e.OldValue, (Visibility)e.NewValue);
}
}
private void OnMyVisibilityChanged(Visibility oldValue, Visibility newValue)
{
Visibility = newValue;
}
public Visibility MyVisibility
{
get { return (Visibility)GetValue(MyVisibilityProperty); }
set { SetValue(MyVisibilityProperty, value); }
}
#endregion public Visibility MyVisibility
}
Here is a small snippet of the XAML.
<DataGrid ....>
<DataGrid.Columns>
<MyDataGridTextColumn Header="User Name"
Foreground="#FFFFFFFF"
Binding="{Binding User.UserName}"
MinWidth="150"
CanUserSort="True"
CanUserResize="False"
CanUserReorder="True"
MyVisibility="{Binding Converter={StaticResource BoolToVisibilityConverter}, Path=ShouldShowUser}"/>
<DataGridTextColumn .../>
</DataGrid.Columns>
</DataGrid>
A couple important facts.
The Converter is indeed defined above in the local resources.
The Converter is correct, it is used many other places in the solution.
If I replace the {Binding} syntax for the MyVisibility property with "Collapsed" the Column does in fact disappear.
If I create a new DependencyProperty (i.e. string Foo), and bind to it I receive the AG_E_PARSER_BAD_PROPERTY_VALUE exception too.
Does anybody have any ideas as to why this isn't working?
Here's the solution I've come up with using a little hack.
First, you need to inherit from DataGrid.
public class DataGridEx : DataGrid
{
public IEnumerable<string> HiddenColumns
{
get { return (IEnumerable<string>)GetValue(HiddenColumnsProperty); }
set { SetValue(HiddenColumnsProperty, value); }
}
public static readonly DependencyProperty HiddenColumnsProperty =
DependencyProperty.Register ("HiddenColumns",
typeof (IEnumerable<string>),
typeof (DataGridEx),
new PropertyMetadata (HiddenColumnsChanged));
private static void HiddenColumnsChanged(object sender,
DependencyPropertyChangedEventArgs args)
{
var dg = sender as DataGrid;
if (dg==null || args.NewValue == args.OldValue)
return;
var hiddenColumns = (IEnumerable<string>)args.NewValue;
foreach (var column in dg.Columns)
{
if (hiddenColumns.Contains ((string)column.GetValue (NameProperty)))
column.Visibility = Visibility.Collapsed;
else
column.Visibility = Visibility.Visible;
}
}
}
The DataGridEx class adds a new DP for hiding columns based on the x:Name of a DataGridColumn and its descendants.
To use in your XAML:
<my:DataGridEx x:Name="uiData"
DataContext="{Binding SomeDataContextFromTheVM}"
ItemsSource="{Binding Whatever}"
HiddenColumns="{Binding HiddenColumns}">
<sdk:DataGridTextColumn x:Name="uiDataCountOfItems">
Header="Count"
Binding={Binding CountOfItems}"
</sdk:DataGridTextColumn>
</my:DataGridEx>
You need to add these to your ViewModel or whatever data context you use.
private IEnumerable<string> _hiddenColumns;
public IEnumerable<string> HiddenColumns
{
get { return _hiddenColumns; }
private set
{
if (value == _hiddenColumns)
return;
_hiddenColumns = value;
PropertyChanged (this, new PropertyChangedEventArgs("HiddenColumns"));
}
}
public void SomeWhereInYourCode ()
{
HiddenColumns = new List<string> {"uiDataCountOfItems"};
}
To unhide, you only need to remove the corresponding name from the list or recreate it without the unhidden name.
I have another solution to this problem that uses an approach similar to the "Binding" property that you find on DataGridTextColumn. Since the column classes are DependencyObjects, you can't directly databind to them, BUT if you add a reference to a FrameworkElement that implements INotifyPropertyChanged you can pass a databinding through to the element, and then use a dependency property to notify the Column that the databinding has changed.
One thing to note is that having the binding on the Column itself instead of the Grid will probably mean that you will want to use a DataContextProxy to get access to the field that you want to bind the Visibility to (the column binding will default to the scope of the ItemSource).
using System;
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
namespace XYZ.Controls
{
public class ExtendedDataGridTextColumn : DataGridTextColumn
{
private readonly Notifier _e;
private Binding _visibilityBinding;
public Binding VisibilityBinding
{
get { return _visibilityBinding; }
set
{
_visibilityBinding = value;
_e.SetBinding(Notifier.MyVisibilityProperty, _visibilityBinding);
}
}
public ExtendedDataGridTextColumn()
{
_e = new Notifier();
_e.PropertyChanged += ToggleVisibility;
}
private void ToggleVisibility(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == "Visibility")
this.Visibility = _e.MyVisibility;
}
//Notifier class is just used to pass the property changed event back to the column container Dependency Object, leaving it as a private inner class for now
private class Notifier : FrameworkElement, INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public Visibility MyVisibility
{
get { return (Visibility)GetValue(MyVisibilityProperty); }
private set { SetValue(MyVisibilityProperty, value); }
}
public static readonly DependencyProperty MyVisibilityProperty = DependencyProperty.Register("MyVisibility", typeof(Visibility), typeof(Notifier), new PropertyMetadata(MyVisibilityChanged));
private static void MyVisibilityChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var n = d as Notifier;
if (n != null)
{
n.MyVisibility = (Visibility) e.NewValue;
n.PropertyChanged(n, new PropertyChangedEventArgs("Visibility"));
}
}
}
}
}
The datagrid column inherits from DependencyObject instead of FrameworkElement. In WPF this would be no big deal... but in silverlight you can only bind to FrameworkElement objects. So you get the descriptive error message of AG_E_PARSER_BAD_PROPERTY_VALUE when you try.
I don't know how much this will help, but I've run into the lack of dependency property problem with data grid columns myself in my latest project. What I did to get around it, was to create an event in the grid column view model, then when the grid is being assembled in the client, use a closure to subscribe the grid column to the column view model. My particular problem was around width. It starts with the view model class for the grid column, which looks something like this pseudo-code:
public delegate void ColumnResizedEvent(double width);
public class GridColumnViewModel : ViewModelBase
{
public event ColumnResizedEvent ColumnResized;
public void Resize(double newContainerWidth)
{
// some crazy custom sizing calculations -- don't ask...
ResizeColumn(newWidth);
}
public void ResizeColumn(double width)
{
var handler = ColumnResized;
if (handler != null)
handler(width);
}
}
Then there's the code that assembles the grid:
public class CustomGrid
{
public CustomGrid(GridViewModel viewModel)
{
// some stuff that parses control metadata out of the view model.
// viewModel.Columns is a collection of GridColumnViewModels from above.
foreach(var column in viewModel.Columns)
{
var gridCol = new DataGridTextColumn( ... );
column.ColumnResized += delegate(double width) { gridCol.Width = new DataGridLength(width); };
}
}
}
When the datagrid is resized in the application, the resize event is picked up and calls the resize method on the viewmodel the grid is bound to. This in turn calls the resize method of each grid column view model. The grid column view model then raises the ColumnResized event, which the data grid text column is subscribed to, and it's width is updated.
I realise this isn't directly solving your problem, but it was a way I could "bind" a view model to a data grid column when there are no dependency properties on it. The closure is a simple construct that nicely encapsulates the behaviour I wanted, and is quite understandable to someone coming along behind me. I think it's not too hard to imagine how it could be modified to cope with visibility changing. You could even wire the event handler up in the load event of the page/user control.
Chris Mancini,
you do not create binding to "Binding" property of data grid column. Well, you write "{Binding User.UserName}", but it doesn't create binding, because (as zachary said) datagrid column doesn't inherit from FrameworkElement and hasn't SetBinding method.
So expression "{Binding User.UserName}" simply creates Binding object and assign it to Binding property of column (this property is type of Binding).
Then datagrid column while generates cells content (GenerateElement - protected method) uses this Binding object to set binding on generated elements (e.g. on Text property of generated TextBlock) which are FrameworkElements
GreatTall1's solution is great, but it need to bit change to make it work.
var n = d as Notifier;
if (n != null)
{
//Assign value in the callback will break the binding.
//n.MyVisibility = (Visibility)e.NewValue;
n.PropertyChanged(n, new PropertyChangedEventArgs("Visibility"));
}
Note that the problem isn't just as simple as 'Visibility' not being a dependency property. In a DataGrid the columns aren't part of the visual 'tree' so you can't use AncestorType even in WPF (or Silverlight 5).
Here's a couple WPF related links (please comment if any of these work for Silverlight - sorry I don't have time to test now)
Has a really nice explanation of the problem and failures of certain solutions (and a clever solution):
http://tomlev2.wordpress.com/2011/03/21/wpf-how-to-bind-to-data-when-the-datacontext-is-not-inherited/
And a couple StackOverflow questions:
WPF Hide DataGridColumn via a binding
Binding Visible property of a DataGridColumn in WPF DataGrid
This works on a data grid template column:
public class ExtendedDataGridColumn : DataGridTemplateColumn
{
public static readonly DependencyProperty VisibilityProperty = DependencyProperty.Register("Visibility", typeof(Visibility), typeof(DataGridTemplateColumn), new PropertyMetadata(Visibility.Visible, VisibilityChanged));
public new Visibility Visibility
{
get { return (Visibility)GetValue(VisibilityProperty); }
set { SetValue(VisibilityProperty, value); }
}
private static void VisibilityChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if ((DataGridTemplateColumn)d != null)
{
((DataGridTemplateColumn)d).Visibility = (Visibility)e.NewValue;
}
}
}
From your MyDataGridTextColumn class, you could get the surrounding DataGrid.
Then you get your ViewModel out of the DataContext of the DataGrid and add a handler to the PropertyChanged event of your ViewModel. In the handler you just check for the property name and its value and change the Visibility of the Column accordingly.
Its not quite the best solution, but it should work ;)

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