WPF binding - DataGrid.Items.Count - wpf

in my View, there are a DataGrid and a TextBox, which is bound to the DataGrid's Items.Count property:
<DataGrid x:Name="dataGrid" ItemsSource="{Binding dataTable}"/>
<TextBox Text="{Binding Items.Count,ElementName=dataGrid,Mode=OneWay,StringFormat={}{0:#}}"/>
The ViewModel has a property (e.g. ItemsCount) which I'd like to be bound to the Items.Count property of the DataGrid, but have no idea, how to achieve this.
class ViewModel : INotifyPropertyChanged
{
public DataTable dataTable {get;set;}
public int ItemsCount {get;set;}
}
Maybe I could also use the Rows.Count property of the DataTable the DataGrid is bound to, but how would i bind or link the two properties in the ViewModel?
So I basically want the ItemsCount property to be synchronized with the dataTable.Rows.Count property.

A common way to achieve your requirements are to declare properties to data bind to the UI controls:
<DataGrid x:Name="dataGrid" ItemsSource="{Binding Items}" />
<TextBox Text="{Binding ItemsCount}" />
...
// You need to implement the INotifyPropertyChanged interface properly here
private ObservableCollection<YourDataType> items = new ObservableCollection<YourDataType>();
public ObservableCollection<YourDataType> Items
{
get { return items; }
set { items = value; NotifyPropertyChanged("Items"); NotifyPropertyChanged("ItemCount"); }
}
public string ItemCount
{
get { Items.Count.ToString("{0:#}"); }
}
UPDATE >>>
As #Sivasubramanian has added his own requirement to your question, in case you need to update the item count specifically by adding to your collection, you can manually call the NotifyPropertyChanged method:
Items.Add(new YourDataType());
NotifyPropertyChanged("ItemCount");

Related

Cell value of a datagrid in mvvm

How to get the cell value of a datagrid in MVVM.i am not selecting anything just i want the value of 2nd row first column.
Normally your Datagrind is bound to a Property on your Viewmodel. simply access that Property in your Viewmodel and get the Values you need.
In ViewModel you have a Property:
public ObservableCollection<Characteristic> Items{get;set;}
Characteristics Class
public class Characteristic : ObservableObject
{
private string _name;
public string Name
{
get { return _name; }
set
{
_name = value;
RaisePropertyChanged("Name");
}
}
}
In XAML:
<DataGrid Margin="0" Grid.Row="1" ItemsSource="{Binding Items}" AutoGenerateColumns="True" />
You just access the Items Property on your ViewModel and get the second item of the Collection.

DatagridComboBoxColumn.ItemsSource does not reflect changes from source other than the source bound for datagrid

ComboBox items do not reflect changes made from its source
Here is what I am trying to accomplish:
I have a WPF datagrid that binding to a database table, inside the datagrid there is a combobox(group ID) column bind to one of the columns from the database table; the combobox items are from another table(a list of group ID). The problem now is when the groupd ID list is changed from other table, the combo box items does not take effect.
Can anyone help? Have been stuct for a long time.
Here is XAML code:
<DataGridTemplateColumn Header="Group ID">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<TextBlock Text="{Binding GroupID, Mode=OneWay}"/>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
<DataGridTemplateColumn.CellEditingTemplate>
<DataTemplate>
<ComboBox Name="ComboBoxTeamGrpID" SelectedItem="{Binding GroupID, Mode=TwoWay}" ItemsSource="{StaticResource ResourceKey=GroupIDList}">
</ComboBox>
</DataTemplate>
</DataGridTemplateColumn.CellEditingTemplate>
</DataGridTemplateColumn>
Here is the code for GroupIDList:
public class GroupIDList : List<string>
{
public GroupIDList()
{
try
{
string tmp = ConfigurationManager.AppSettings["DataSvcAddress"];
Uri svcUri = new Uri(tmp);
JP790DBEntities context = new JP790DBEntities(svcUri);
var deviceQry = from o in context.Devices
where o.GroupID == true
select o;
DataServiceCollection<Device> cList = new DataServiceCollection<Device>(deviceQry);
for (int i = 0; i < cList.Count; i++)
{
this.Add(cList[i].ExtensionID.Trim());
}
this.Add("None");
//this.Add("1002");
//this.Add("1111");
//this.Add("2233");
//this.Add("5544");
}
catch (Exception ex)
{
string str = ex.Message;
}
}
}
Here is another problem related, can anyone help? thank you.
It is either because your GroupIdList is a List and not an ObservableCollection, or because you're binding to a StaticResource, which WPF assumes is unchanged so is only loaded once.
Change your List<string> to an ObservableCollection<string> which will automatically notify the UI when it's collection gets changed, and if that still doesn't work than change your ItemsSource from a StaticResource to a RelativeSource binding, such as
ItemsSource="{Binding
RelativeSource={RelativeSource AncestorType={x:Type DataGrid}},
Path=DataContext.GroupIdList}"
Edit
Your parent ViewModel which has your DataGrid's ItemsSource collection should look something like below. Simply add another public property for GroupIdList and have it return your list. Then use the above RelativeSource binding to access it, assuming your DataGrid's ItemsSource is bound in the form of <DataGrid ItemsSource="{Binding MyDataGridItemsSource}" ... />
public class MyViewModel
{
private ObservableCollection<MyDataObject> _myDataGridItemsSource;
public ObservableCollection<MyDataObject> MyDataGridItemsSource
{
get { return _myDataGridItemsSource; }
set
{
if (value != _myDataGridItemsSource)
{
_myObjects = value;
ReportPropertyChanged("MyDataGridItemsSource");
}
}
}
private ObservableCollection<string> _groupIdList = new GroupIdList();
public ObservableCollection<string> GroupIdList
{
get { return _groupIdList; }
}
}
WPF will not poll everytime and check if your list changed. In Order to do this, as Rachel pointed at you should do something like :
public class GroupIDList : ObseravableCollection<string>
EDIT :
Here is my suggestion :
I actually wouldn't do it the way you did. What I do is I create a View Model for the whole grid, that looks like :
public class MyGridViewModel : DependencyObject
Which I would use as data context for my grid:
DataContext = new MyGridViewModel ();
Now the implementation of MyGridViewModel will contain a list of ViewModel that represent my GridRows, which is an ObservableCollection
public ObservableCollection<RowGridViewModel> RowItemCollection { get; private set; }
I will this in my dataGrid as such :
<Grid>
<DataGrid AutoGenerateColumns="False" ItemsSource="{Binding RowItemCollection}" SelectionMode="Extended" SelectionUnit="Cell">
<DataGrid.Columns>
and All you need to do, is to fill in you RowItemColleciton with the correct data, and then bind you Columns to the correct Property in RowGridViewModel...in your case it would look like (but you have to initialize the GroupIDList :
public class RowGridViewModel: DependencyObject
{
public List<String> GroudIDList { get; set;
}
}
Let me if that help

ListView's ItemsSource binding not pushing changes to source

I am using WPF and Mvvm and my ListView has its ItemSource bound to an ICollectionView. How do I handle selected item change event?
Originally I had a DataGrid's ItemSource bind to the same ICollectionView and setup the collection's CurrentChanged event. Everything works fine, but not the case for a ListView.
All you have to do, as Thomas mentioned is to bind the SelectedItem Attribute of the listbox to a property in the viewmodel. To make it clear, here's an example.
Here's my view
<Grid x:Name="LayoutRoot" Background="White">
<ListView ItemsSource="{Binding Contacts}" SelectedItem="{Binding SelectedContact, Mode=TwoWay}">
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</Grid>
And here's my ViewModel
public class MainViewModel: ViewModelBase
{
ObservableCollection<ContactViewModel> contacts;
ContactViewModel selectedContact;
public ContactViewModel SelectedContact
{
get { return selectedContact; }
set {
selectedContact = value;
base.OnPropertyChanged("SelectedContact");
}
}
public ObservableCollection<ContactViewModel> Contacts
{
get { return contacts; }
set {
contacts = value;
base.OnPropertyChanged("Contacts");
}
}
}
Everytime you try changing the selection in the listbox you'll step into the setter of the SelectedContact.
set
{
contacts = value;
base.OnPropertyChanged("Contacts");
}
Through this, you'll know that the selected contact has changed.
Using the property SelectedContact, you'll also know which of the item in your collection is selected.
You can also bind a Collection property in the ViewModel to the SelectedItems attribute of the ListView if you want to implement multiple selection.
Just bind the SelectedItem of the ListView to a property of your ViewModel

Trigger Filter on CollectionViewSource

I am working on a WPF desktop application using the MVVM pattern.
I am trying to filter some items out of a ListView based on the text typed in a TextBox. I want the ListView items to be filtered as I change the text.
I want to know how to trigger the filter when the filter text changes.
The ListView binds to a CollectionViewSource, which binds to the ObservableCollection on my ViewModel. The TextBox for the filter text binds to a string on the ViewModel, with UpdateSourceTrigger=PropertyChanged, as it should be.
<CollectionViewSource x:Key="ProjectsCollection"
Source="{Binding Path=AllProjects}"
Filter="CollectionViewSource_Filter" />
<TextBox Text="{Binding Path=FilterText, UpdateSourceTrigger=PropertyChanged}" />
<ListView DataContext="{StaticResource ProjectsCollection}"
ItemsSource="{Binding}" />
The Filter="CollectionViewSource_Filter" links to an event handler in the code behind, which simply calls a filter method on the ViewModel.
Filtering is done when the value of FilterText changes - the setter for the FilterText property calls a FilterList method that iterates over the ObservableCollection in my ViewModel and sets a boolean FilteredOut property on each item ViewModel.
I know the FilteredOut property is updated when the filter text changes, but the List does not refresh. The CollectionViewSource filter event is only fired when I reload the UserControl by switching away from it and back again.
I've tried calling OnPropertyChanged("AllProjects") after updating the filter info, but it did not solve my problem.
("AllProjects" is the ObservableCollection property on my ViewModel to which the CollectionViewSource binds.)
How can I get the CollectionViewSource to refilter itself when the value of the FilterText TextBox changes?
Many thanks
Don't create a CollectionViewSource in your view. Instead, create a property of type ICollectionView in your view model and bind ListView.ItemsSource to it.
Once you've done this, you can put logic in the FilterText property's setter that calls Refresh() on the ICollectionView whenever the user changes it.
You'll find that this also simplifies the problem of sorting: you can build the sorting logic into the view model and then expose commands that the view can use.
EDIT
Here's a pretty straightforward demo of dynamic sorting and filtering of a collection view using MVVM. This demo doesn't implement FilterText, but once you understand how it all works, you shouldn't have any difficulty implementing a FilterText property and a predicate that uses that property instead of the hard-coded filter that it's using now.
(Note also that the view model classes here don't implement property-change notification. That's just to keep the code simple: as nothing in this demo actually changes property values, it doesn't need property-change notification.)
First a class for your items:
public class ItemViewModel
{
public string Name { get; set; }
public int Age { get; set; }
}
Now, a view model for the application. There are three things going on here: first, it creates and populates its own ICollectionView; second, it exposes an ApplicationCommand (see below) that the view will use to execute sorting and filtering commands, and finally, it implements an Execute method that sorts or filters the view:
public class ApplicationViewModel
{
public ApplicationViewModel()
{
Items.Add(new ItemViewModel { Name = "John", Age = 18} );
Items.Add(new ItemViewModel { Name = "Mary", Age = 30} );
Items.Add(new ItemViewModel { Name = "Richard", Age = 28 } );
Items.Add(new ItemViewModel { Name = "Elizabeth", Age = 45 });
Items.Add(new ItemViewModel { Name = "Patrick", Age = 6 });
Items.Add(new ItemViewModel { Name = "Philip", Age = 11 });
ItemsView = CollectionViewSource.GetDefaultView(Items);
}
public ApplicationCommand ApplicationCommand
{
get { return new ApplicationCommand(this); }
}
private ObservableCollection<ItemViewModel> Items =
new ObservableCollection<ItemViewModel>();
public ICollectionView ItemsView { get; set; }
public void ExecuteCommand(string command)
{
ListCollectionView list = (ListCollectionView) ItemsView;
switch (command)
{
case "SortByName":
list.CustomSort = new ItemSorter("Name") ;
return;
case "SortByAge":
list.CustomSort = new ItemSorter("Age");
return;
case "ApplyFilter":
list.Filter = new Predicate<object>(x =>
((ItemViewModel)x).Age > 21);
return;
case "RemoveFilter":
list.Filter = null;
return;
default:
return;
}
}
}
Sorting kind of sucks; you need to implement an IComparer:
public class ItemSorter : IComparer
{
private string PropertyName { get; set; }
public ItemSorter(string propertyName)
{
PropertyName = propertyName;
}
public int Compare(object x, object y)
{
ItemViewModel ix = (ItemViewModel) x;
ItemViewModel iy = (ItemViewModel) y;
switch(PropertyName)
{
case "Name":
return string.Compare(ix.Name, iy.Name);
case "Age":
if (ix.Age > iy.Age) return 1;
if (iy.Age > ix.Age) return -1;
return 0;
default:
throw new InvalidOperationException("Cannot sort by " +
PropertyName);
}
}
}
To trigger the Execute method in the view model, this uses an ApplicationCommand class, which is a simple implementation of ICommand that routes the CommandParameter on buttons in the view to the view model's Execute method. I implemented it this way because I didn't want to create a bunch of RelayCommand properties in the application view model, and I wanted to keep all the sorting/filtering in one method so that it was easy to see how it's done.
public class ApplicationCommand : ICommand
{
private ApplicationViewModel _ApplicationViewModel;
public ApplicationCommand(ApplicationViewModel avm)
{
_ApplicationViewModel = avm;
}
public void Execute(object parameter)
{
_ApplicationViewModel.ExecuteCommand(parameter.ToString());
}
public bool CanExecute(object parameter)
{
return true;
}
public event EventHandler CanExecuteChanged;
}
Finally, here's the MainWindow for the application:
<Window x:Class="CollectionViewDemo.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:CollectionViewDemo="clr-namespace:CollectionViewDemo"
Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
<CollectionViewDemo:ApplicationViewModel />
</Window.DataContext>
<DockPanel>
<ListView ItemsSource="{Binding ItemsView}">
<ListView.View>
<GridView>
<GridViewColumn DisplayMemberBinding="{Binding Name}"
Header="Name" />
<GridViewColumn DisplayMemberBinding="{Binding Age}"
Header="Age"/>
</GridView>
</ListView.View>
</ListView>
<StackPanel DockPanel.Dock="Right">
<Button Command="{Binding ApplicationCommand}"
CommandParameter="SortByName">Sort by name</Button>
<Button Command="{Binding ApplicationCommand}"
CommandParameter="SortByAge">Sort by age</Button>
<Button Command="{Binding ApplicationCommand}"
CommandParameter="ApplyFilter">Apply filter</Button>
<Button Command="{Binding ApplicationCommand}"
CommandParameter="RemoveFilter">Remove filter</Button>
</StackPanel>
</DockPanel>
</Window>
Nowadays, you often don't need to explicitly trigger refreshes. CollectionViewSource implements ICollectionViewLiveShaping which updates automatically if IsLiveFilteringRequested is true, based upon the fields in its LiveFilteringProperties collection.
An example in XAML:
<CollectionViewSource
Source="{Binding Items}"
Filter="FilterPredicateFunction"
IsLiveFilteringRequested="True">
<CollectionViewSource.LiveFilteringProperties>
<system:String>FilteredProperty1</system:String>
<system:String>FilteredProperty2</system:String>
</CollectionViewSource.LiveFilteringProperties>
</CollectionViewSource>
CollectionViewSource.View.Refresh();
CollectionViewSource.Filter is reevaluated in this way!
Perhaps you've simplified your View in your question, but as written, you don't really need a CollectionViewSource - you can bind to a filtered list directly in your ViewModel (mItemsToFilter is the collection that is being filtered, probably "AllProjects" in your example):
public ReadOnlyObservableCollection<ItemsToFilter> AllFilteredItems
{
get
{
if (String.IsNullOrEmpty(mFilterText))
return new ReadOnlyObservableCollection<ItemsToFilter>(mItemsToFilter);
var filtered = mItemsToFilter.Where(item => item.Text.Contains(mFilterText));
return new ReadOnlyObservableCollection<ItemsToFilter>(
new ObservableCollection<ItemsToFilter>(filtered));
}
}
public string FilterText
{
get { return mFilterText; }
set
{
mFilterText = value;
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("FilterText"));
PropertyChanged(this, new PropertyChangedEventArgs("AllFilteredItems"));
}
}
}
Your View would then simply be:
<TextBox Text="{Binding Path=FilterText,UpdateSourceTrigger=PropertyChanged}" />
<ListView ItemsSource="{Binding AllFilteredItems}" />
Some quick notes:
This eliminates the event in the code behind
It also eliminates the "FilterOut" property, which is an artificial, GUI-only property and thus really breaks MVVM. Unless you plan to serialize this, I wouldn't want it in my ViewModel, and certainly not in my Model.
In my example, I use a "Filter In" rather than a "Filter Out". It seems more logical to me (in most cases) that the filter I am applying are things I do want to see. If you really want to filter things out, just negate the Contains clause (i.e. item => ! Item.Text.Contains(...)).
You may have a more centralized way of doing your Sets in your ViewModel. The important thing to remember is that when you change the FilterText, you also need to notify your AllFilteredItems collection. I did it inline here, but you could also handle the PropertyChanged event and call PropertyChanged when the e.PropertyName is FilterText.
Please let me know if you need any clarifications.
If I understood well what you are asking:
In the set part of your FilterText property just call Refresh() to your CollectionView.
I just discovered a much more elegant solution to this issue. Instead of creating a ICollectionView in your ViewModel (as the accepted answer suggests) and setting your binding to
ItemsSource={Binding Path=YourCollectionViewSourceProperty}
The better way is to create a CollectionViewSource property in your ViewModel. Then bind your ItemsSource as follows
ItemsSource={Binding Path=YourCollectionViewSourceProperty.View}
Notice the addition of .View This way the ItemsSource binding is still notified whenever there is a change to the CollectionViewSource and you never have to manually call Refresh() on the ICollectionView
Note: I can't determine why this is the case. If you bind directly to a CollectionViewSource property the binding fails. However, if you define a CollectionViewSource in your Resources element of a XAML file and you bind directly to the resource key, the binding works fine. The only thing I can guess is that when you do it completely in XAML it knows you really want to bind to the CollectionViewSource.View value and binds it for you acourdingly behind the scenes (how helpful! :/) .

CheckedItems property for custom CheckBoxList control in Silverlight

I need to implement CheckBoxList control with ItemsSource and CheckedItems properties. Items from ItemsSource should be displayed as checked checkboxes if CheckedItems contains these values or unchecked otherwise. Also I need two-way databinding support for CheckedItems property (value of this property should be updated when user clicks on checkboxes).
Here some code which probably can help to understand my problem
XAML:
<UserControl x:Class="Namespace.Controls.CheckBoxList" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ListBox x:Name="LayoutRoot">
<ListBox.ItemTemplate>
<DataTemplate>
<CheckBox Content="{Binding}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</UserControl>
Code behind:
public partial class CheckBoxList : UserControl
{
public static readonly DependencyProperty ItemsSourceProperty = DependencyProperty.Register("ItemsSource", typeof(IEnumerable), typeof(CheckBoxList), null);
public static readonly DependencyProperty CheckedItemsProperty = DependencyProperty.Register("CheckedItems", typeof(IEnumerable), typeof(CheckBoxList), null);
public IEnumerable ItemsSource
{
get { return (IEnumerable)GetValue(ItemsSourceProperty); }
set { SetValue(ItemsSourceProperty, value); }
}
public IEnumerable CheckedItems
{
get { return (IEnumerable)GetValue(CheckedItemsProperty); }
set { SetValue(CheckedItemsProperty, value); }
}
public CheckBoxList()
{
InitializeComponent();
LayoutRoot.SetBinding(ItemsControl.ItemsSourceProperty, new Binding("ItemsSource") { Source = this });
}
}
I think that I need to bind ListBox to UserControl with custom converter, which will return collection of items with additional IsChecked property, but it works only in case of one-way data binding.
Looks like I need two-way binding to two properties at one time, but I don't know how to implement it and will appreciate any help with this issue.
Thanks in advance.
First of all you should consider deriving from ListBox rather than UserControl. The ListBox already does most of what you want.
Secondly consider one way binding to an IList. You can then add and remove entires to that IList as the respective items are selected.
Rather than try to bind a CheckBox control in an Item Template you make a copy of the ListBox styles, place them in Generic.xaml as the style of your new control. Then modify the unselected and selected visual states using a checked and unchecked check box as part of the visual appearance.
Now you can attach to the SelectionChanged event and use the Event args AddedItems list to add to the bound IList and the RemovedItems list to remove items from the bound list.
You would need to clear and re-add the set of items to the list box SelectedItems list when either your CheckedItems is assigned or the ItemsSource is changed.
There are probably a number gotchas that you will need to work round but this seems like a more direct path to your goal than starting from scratch with a UserControl base.
Add an observable collection for your list box datasource to your datacontext:
private ObservableCollection<MyItem> _myItems;
public ObservableCollection<MyItem> MyItems
{
get { return _searchByFields; }
set
{
_myItems = value;
}
}
Add a class to hold the data about your checkboxes:
public class MyItem
{
public bool Checked {get; set; }
public string MyItemValue { set ; set; }
}
Then in your data template bind listbox to the collection and your data template checkboxes to the respective MyItem properties:
<UserControl x:Class="Namespace.Controls.CheckBoxList"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ListBox x:Name="LayoutRoot"
DataContext="[Dataconext here]"
ItemsSource={Binding MyItems}>
<ListBox.ItemTemplate>
<DataTemplate>
<CheckBox IsChecked="{Binding Checked, Mode=TwoWay}"
Content="{Binding MyItemValue}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</UserControl>
Don't forget to set the DataContext of the binding to the appropriate class (you might be doing this in the XAML or the code behind perhaps)

Resources