So, my set up is like this:
My MainWindow has a TabControl with 5 tabs. To keep the code in my file clean I decided the 5 tabs their content into 5 UserControls.
In let say tab 1 has UserControl Customers (View: CustomersView, ViewModel: CustomersViewModel) with a ComboBox. The ComboBox is ItemSource is bound to a ObservableCollection(Of String) which is filled by DbServiceKlant.GetKlantenlijst.
Also in tab 1 I have a button to add a new Customer to the database. This opens another UserControl which overlays the entire MainWindow.
This 2nd UserControl (View: AddCustomerView, ViewModel: AddCustomerViewModel) has some form to fill in, has a Sub to ass the data to the database.
I first did this all in the MainWindow but the code has taken on sushi proportions (both in .xaml and .xaml.vb) that it isn't maintainable anymore. Having everything in 1 file, it's easy to pass variables and add items to a ObservableCollection.
With everything split up in UserControls, it has been a question to me how I'm going to achieve this. Basically:
UserControl Customers has a ObservableCollection filled with Customer and a button to open UserControl AddCustomer.
In UserControl AddCustomer I have a button which can add the filled in form to the database.
Now the question is:
How do I open UserControl AddCustomer from Customers?
How do I update my ObservableCollection in Customers if I close AddCustomer?
When everything was in 1 file I just manipulated Visibility of AddCustomer and could update the ObservableCollection.
This is a snippet from Customers.
<ComboBox Background="White" ItemsSource="{Binding Klantenlijst}" SelectedItem="{Binding SelectedKlant}" Grid.Column="1" Grid.Row="0" Grid.ColumnSpan="4" />
<Button Grid.Column="5" Command="{Binding OpenAddKlant}" ToolTip="Nieuwe klant">
<Image Source="/Images/Add.png" />
</Button>
The ObservableCollection.
Private _oKlantenlijst As ObservableCollection(Of String) = DbServiceKlant.GetKlantenlijst
Public Property Klantenlijst As ObservableCollection(Of String)
Get
Return _oKlantenlijst
End Get
Set(ByVal value As ObservableCollection(Of String))
_oKlantenlijst = value
OnPropertyChanged()
End Set
End Property
The ICommand:
Private _oOpenAddKlant As New RelayCommand(AddressOf OpenAddKlantSub)
Public ReadOnly Property OpenAddKlant As RelayCommand
Get
Return _oOpenAddKlant
End Get
End Property
And the actual Sub
Public Sub OpenAddKlantSub()
' I think here should be the code to open the AddCustomer UserControl
End Sub
In my 1 file application (which I'm converting to UserControls), the AddCustomer popup had this Sub
Private Sub PopUpAddKlantAdd(sender As Object, e As RoutedEventArgs)
Try
If PupAddKlaNaa.Equals("") OrElse PupAddKlaStr.Equals("") OrElse PupAddKlaGem.Equals("") Then
MessageBox.Show("U moet minstens de naam, straat en gemeente invullen om een nieuwe klant aan te kunnen maken.", "Geen gegevens", MessageBoxButton.OK, MessageBoxImage.Information)
Else
DbServiceKlant.Create(PupAddKlaNaa, PupAddKlaStr, PupAddKlaNr_, PupAddKlaBus, PupAddKlaPos, PupAddKlaGem, PupAddKlaLan, PupAddKlaTel, PupAddKlaBTW)
_oKlant = DbServiceKlant.GetDetails(PupAddKlaNaa)
PopUpAddKlantClose()
PopUpAddKlantClear()
VoGetNaamKlanten()
VoFillDetailsKlant(_oKlant)
VoKlaSel = _oKlant.Naam
End If
Catch ex As Exception
ExceptionLogger.Log(ex, 1)
End Try
End Sub
Related
I have a DataGrid with many items and I need to programmatically scroll to the SelectedItem. I have searched on StackOverflow and Google, and it seems the solution is ScrollIntoView, as follows:
grid.ScrollIntoView(grid.SelectedItem)
which scrolls the DataGrid up or down until the selected item is in focus. However, depending on the current scroll position relative to the selected item, the selected item may end up being the last visible item in the DataGrid's ScrollViewer. I want that the selected item will be the first visible item in the ScrollViewer (assuming there are enough rows in the DataGrid to allow this). So I tried this:
'FindVisualChild is a custom extension method that searches in the visual tree and returns
'the first element of the specified type
Dim sv = grid.FindVisualChild(Of ScrollViewer)
If sv IsNot Nothing Then sv.ScrollToEnd()
grid.ScrollIntoView(grid.SelectedItem)
First I scroll to the end of the DataGrid and only then do I scroll to the SelectedItem, at which point the SelectedItem is shown at the top of the DataGrid.
My problem is that scrolling to the end of the DataGrid works well, but subsequently scrolling to the selected item doesn't always work.
How can I resolve this issue, or is there any other alternative strategy for scrolling to a specific record in the top position?
You were on the right track, just try to work with collection view instead of working directly on the datagrid for this kind of needs.
Here is a working example where the desired item is always displayed as first selected item if possible, otherwise the scrollviewer is scrolled to the end and the target item is selected at its position.
The key points are :
Use CollectionView on the business side and enable current item synch on the XAML control (IsSynchronizedWithCurrentItem=true)
Defer the "real" target scroll in order to allow the "Select Last item" to be visualy executed (By using a Dispatcher.BeginInvoke with a low priority)
Here is the business logic (This is automatic convertion from C# to VB)
Public Class Foo
Public Property FooNumber As Integer
Get
End Get
Set
End Set
End Property
End Class
Public Class MainWindow
Inherits Window
Implements INotifyPropertyChanged
Private _myCollectionView As ICollectionView
Public Sub New()
MyBase.New
DataContext = Me
InitializeComponent
MyCollection = New ObservableCollection(Of Foo)
MyCollectionView = CollectionViewSource.GetDefaultView(MyCollection)
Dim i As Integer = 0
Do While (i < 50)
MyCollection.Add(New Foo)
i = (i + 1)
Loop
End Sub
Public Property MyCollectionView As ICollectionView
Get
Return Me._myCollectionView
End Get
Set
Me._myCollectionView = value
Me.OnPropertyChanged("MyCollectionView")
End Set
End Property
Private Property MyCollection As ObservableCollection(Of Foo)
Get
End Get
Set
End Set
End Property
Private Sub ButtonBase_OnClick(ByVal sender As Object, ByVal e As RoutedEventArgs)
Dim targetNum As Integer = Convert.ToInt32(targetScroll.Text)
Dim targetObj As Foo = Me.MyCollection.FirstOrDefault(() => { }, (r.FooNumber = targetNum))
'THIS IS WHERE THE MAGIC HAPPENS
If (Not (targetObj) Is Nothing) Then
'Move to the collection view to the last item
Me.MyCollectionView.MoveCurrentToLast
'Bring this last item into the view
Dim current = Me.MyCollectionView.CurrentItem
itemsContainer.ScrollIntoView(current)
'This is the trick : Invoking the real target item select with a low priority allows previous visual change (scroll to the last item) to be executed
Dispatcher.BeginInvoke(DispatcherPriority.ContextIdle, New Action(() => { }, Me.ScrollToTarget(targetObj)))
End If
End Sub
Private Sub ScrollToTarget(ByVal targetObj As Foo)
Me.MyCollectionView.MoveCurrentTo(targetObj)
itemsContainer.ScrollIntoView(targetObj)
End Sub
Public Event PropertyChanged As PropertyChangedEventHandler
Protected Overridable Sub OnPropertyChanged(ByVal propertyName As String)
If (Not (PropertyChanged) Is Nothing) Then
PropertyChanged?.Invoke(Me, New PropertyChangedEventArgs(propertyName))
End If
End Sub
End Class
And this is the xaml
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<DataGrid x:Name="itemsContainer" ItemsSource="{Binding MyCollectionView}" IsSynchronizedWithCurrentItem="True" Margin="2" AutoGenerateColumns="False" >
<DataGrid.Columns>
<DataGridTextColumn Binding="{Binding FooNumber}"></DataGridTextColumn>
</DataGrid.Columns>
</DataGrid>
<StackPanel Grid.Column="1">
<TextBox x:Name="targetScroll" Text="2" Margin="2"></TextBox>
<Button Content="Scroll To item" Click="ButtonBase_OnClick" Margin="2"></Button>
</StackPanel>
</Grid>
I Solved this question with following code:
public partial class MainWindow:Window
{
private ObservableCollection<Product> products=new ObservableCollection<Product> ();
public MainWindow()
{
InitializeComponent ();
for (int i = 0;i < 50;i++)
{
Product p=new Product { Name="Product "+i.ToString () };
products.Add (p);
}
lstProduct.ItemsSource=products;
}
private void lstProduct_SelectionChanged(object sender,SelectionChangedEventArgs e)
{
products.Move (lstProduct.SelectedIndex,0);
lstProduct.ScrollIntoView (lstProduct.SelectedItem);
}
}
public class Product
{
public string Name { get; set; }
}
<Grid>
<ListBox Name="lstProduct" Margin="20" DisplayMemberPath="Name" SelectionChanged="lstProduct_SelectionChanged" />
</Grid>
The accepted answer to this other question shows a different approach to get the first/last visible row of such a grid.
You could find out the index of your row and directly scroll there or scroll down row by row until the first visible row matches.
I have a WPF listbox in my window. In the Load event of the window, i create a List(of Object) and I added some items. At application starts or debug, I can see items.
If I add 1 item on the list, i correctly see 1 only item. If I add 3 or more items, i correctly see 3 or more items. If I add 2 only items, i see 1 only item. Why?
Here is my WPF code
<Window x:Class="Cacatua.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:Cacatua;assembly=" >
<Grid>
<ListBox Name="lbSearch" ItemsSource="{Binding}" />
</Grid>
</Window>
And here is my code-behind (same assembly, in Cacatua namespace):
Private myLstSearch As List(Of Object)
Private Sub Window_Loaded(sender As System.Object, e As System.Windows.RoutedEventArgs) Handles MyBase.Loaded
myLstSearch = New List(Of Object)
lbSearch.ItemsSource = myLstSearch
Dim myMedia1 as Media1
myMedia1 = New Media1("IdMedia1-A")
myLstSearch.Add(myMedia1)
myMedia1 = New Media1("IdMedia1-B")
myLstSearch.Add(myMedia1)
End Sub
where Media1 is a simple class that contains a string
Public Class Media1
Private myIdTitolo As String
Public ReadOnly Property IDTitolo As String
Get
Return (myIdTitolo)
End Get
End Property
Public Sub New(str As String)
myIdTitolo = str
End Sub
End Class
With this code, I would see a list with this output (there is no datatemplate):
Cacatua.Media1
Cacatua.Media1
but I see only
Cacatua.Media1
I think it's a bug. But am I the first with this problem?
You've got the right idea, but the problem is your ItemsSource doesn't know when to update since you're not using an ObservableCollection. Also there is a timing issue between rendering and loading the window, and I think this has to do with the fact you aren't properly binding your items source.
For starters, try changing the type of myLstSearch to ObservableCollection(Of Media1).
Also, a better way to do this would be to databind it from the XAML directly, so your code-behind would be something like:
Public property MyListSearch As ObservableCollection(Of Media1)
Then your XAML would look like:
<Window x:Class="Cacatua.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:Cacatua;assembly=">
<Grid>
<ListBox Name="lbSearch" ItemsSource="{Binding Path=MyListSearch}" />
</Grid>
</Window>
That way, you can simply initialize MyListSearch in your window constructor, and then add elements to it whenever, while your view will automatically update.
Goal
To add a list of a custom class object (DamagedItems) to a DataGrid using the Model, View, ViewModel (MVVM) way of doing things.
I want the user to be able to create entries of damaged parts (deemed improper during inspection of a machine).
What I have done
I have created:
A window: wDamagedItems.xaml in which it's DataContext is set to DamagedItemViewModel
A Model: DamagedItemModel.vb which implements INotifyPropertyChanged
A ViewModel: DamagedItemViewModel.vb where I set properties of classes such as my DamagedItemModel
An ObservableCollection: DamagedItemList.vb which inherits an ObservableCollection(Of DamagedItemModel)
Since my DataContext is set to the DamagedItemViewModel, here is how I setup the properties:
Public Class DamagedItemViewModel
Private _DamagedItem As DamagedItemModel
Private _Add As ICommand
Private _DamagedItems As DamagedItemList
Public Property DamagedItem As DamagedItemModel
Get
Return _DamagedItem
End Get
Set(value As DamagedItemModel)
_DamagedItem = value
End Set
End Property
Public Property DamagedItems As DamagedItemList
Get
Return _DamagedItems
End Get
Set(value As DamagedItemList)
_DamagedItems = value
End Set
End Property
Public Property Add As ICommand
Get
Return _Add
End Get
Set(value As ICommand)
_Add = value
End Set
End Property
Public Sub New()
DamagedItem = New DamagedItemModel("", "", "")
DamagedItems = New DamagedItemList
Add = New DamagedItemAddEntryCommand(Me)
End Sub
Public Function CanUpdate() As Boolean
If DamagedItem.Description = "" Then Return False
If DamagedItem.Initiales = "" Then Return False
Return True
End Function
Public Sub AddEntry()
DamagedItems.Add(DamagedItem) 'Items get added to the datagrid
DamagedItem = New DamagedItemModel 'Does not seem to clear textboxes
End Sub
End Class
Here is how my XAML is set up:
<DataGrid ItemsSource="{Binding Path=DamagedItems}" AutoGenerateColumns="True" HorizontalAlignment="Stretch" Margin="12,90,12,0" Name="DataGrid1" VerticalAlignment="Top" Height="229" / >
<TextBox Text="{Binding DamagedItem.Description, UpdateSourceTrigger=PropertyChanged}" Height="23" HorizontalAlignment="Left" Margin="88,24,0,0" VerticalAlignment="Top" Width="249" />
<TextBox Text="{Binding DamagedItem.Initiales, UpdateSourceTrigger=PropertyChanged}" Height="23" HorizontalAlignment="Left" Margin="88,58,0,0" VerticalAlignment="Top" Width="249" />
As you can see, my textboxes are bound to my Model (which is contained in my ViewModel, which is bound to that Window's DataContext). Whenever I click on my "Add" button, whatever is in the textbox gets added to the DataGrid, but the content in the text boxes stay there.
This step is fine, I write in what I want to add and click on "Add"
After clicking on "Add" i get the following results in the DataGrid, which is fine. The issue is my text boxes are still filled with data yet the Model was cleared (see code after DamagedItemViewModel AddEntry method).
Now when I try to add the following text:
Description: "Part is bent"
Initiales: "A.C"
I get the following result:
The first letter typed in the description gets inputted in the first entry of the DataGrid, then it erases the text in the description textbox. Only then can I keep typing what I want. The same thing occurs for the initiales text box.
Any ideas? If you wish to see more of my code, suggest which portion I should add.
Thank you in advance!
Yup, I remember running into this one. You have to implement iNotifyPropertyCHnaged. This is how the viewmodel class "notifies" the user interface that there has been a change to the underlying property of a binding:
look here:
http://msdn.microsoft.com/en-us/library/ms743695.aspx
You will have to implement this for every property you want reflected back to the view. SO what I do is have a base viewmodel class (ViewModelBase which exposes method RasiePropertyChanged) which implements iNotifyPropertyChanged and then my viewmodles inherit from it. Then I notify the property changed in the property set of the property:
ie:
Public Property Selection As job
Get
Return Me._Selection
End Get
Set(ByVal value As job)
If _Selection Is value Then
Return
End If
_PreviousJob = _Selection
_Selection = value
RaisePropertyChanged(SelectionPropertyName)
End Set
End Property
This seems frustrating at first but is needed to keep the decoupling that MVVM supports. Its easy to implement.
I am new to WPF and trying something like this to update a label text in the WPF form from the class.
The onchange event is getting triggered, but not getting displayed on the form
Here is my class
Public Class ExtractDetails
Inherits UserControl
Implements INotifyPropertyChanged
Private _prdFrstName as string
Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
Public Property PrdFrstName() As String
Get
Return _prdFrstName
End Get
Set(ByVal value As String)
If _prdFrstName <> value Then
_prdFrstName = value
Me.OnPropertyChanged("PrdFrstName")
End If
End Set
End Property
Public Sub suMainStrt()
PrdFrstName = strComurl ''contyains teh URL to nagigate to
webBrwFrst = New WebBrowser
webBrwFrst.Navigate(New Uri(strComurl))
Call extract(webBrwFrst, strComurl)
end sub
end class
the url keeps on changing as i ma getting the values from an excel file and looping for each URL.
i wanted to display the URL currently working now
this is my XAML
<Window x:Class="Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Avenet Prduct Description Extractor" Height="396.627" Width="588.123" Background="AliceBlue" Icon="LGIcon.ico">
<Grid Height="341.077" Width="567.721" Background="AliceBlue">
<StackPanel Margin="170.225,226.418,3.143,0" Name="StackPanel1" Height="97.994" VerticalAlignment="Top">
<Label Height="30.906" Name="lblCrntSt1" Content="{Binding Path=PrdFrstName, UpdateSourceTrigger=PropertyChanged}" Width="161" BorderThickness="2" BorderBrush="AliceBlue" Background="Red" Foreground="White" FontSize="13"></Label>
</StackPanel>
</Grid>
and this is my windows class.
Class Window1
Dim clsIniti As New ExtractDetails
Public Sub New()
' This call is required by the Windows Form Designer.
InitializeComponent()
'clsIniti = New ExtractDetails
Me.DataContext = clsIniti
End Sub
end class
without updating the text labels the entire function is working good. but i wish to display few things. where i am going wrong
I tried data binding by removing few parts to new created project. it works there. so some thing wrong in this code??? :`(
I see two possible causes that this doesn't work for you.
A. How does your OnPropertyChanged method look like?
' Correct implementation:
Private Sub OnPropertyChanged(propertyName As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
End Sub
B. Make sure the ExtractDetails instance you call suMainStrt on, is the same as your DataContext instance. Test this by calling suMainStrt directly from the constructor of Window1:
Class Window1
Dim clsIniti As New ExtractDetails
Public Sub New()
' This call is required by the Windows Form Designer.
InitializeComponent()
'clsIniti = New ExtractDetails
Me.DataContext = clsIniti
' test (if this works, your problem is B.)
clsIniti.suMainStrt()
End Sub
End Class
As a side note: Unless you have good reasons to do this, I suggest you create a dedicated viewmodel (class, not usercontrol) that contains the properties you want to bind to.
I have a wpv/mvvm-light/vb.net application with a master/detail view. In this view there is a listbox of clients and a detail view of the client's details where they user can view and edit the customers.
I wanted to add a function where users would be prompted to save changes when a new client is selected in the listbox. If the user chooses yes from the messagebox then save changes and if no then discard changes and return previous selected item back to its original value. I have this all working fine.
My problem is that when the user selects a new client and the messagebox asks them to save changes, the listbox goes out of sync. Meaning that the listbox shows the new client selected but the detail view still shows the previous client. The odd thing is that it works properly on rare occasions.
The following is my view:
<UserControl x:Class="FTC.View.ClientListView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:FTC_Application"
mc:Ignorable="d"
d:DesignHeight="400" d:DesignWidth="900">
<ListBox
Grid.Column="1"
Width="350"
Style="{DynamicResource FTC_ListBox}"
ItemTemplate="{DynamicResource FTC_ClientListTemplate}"
ItemContainerStyle="{DynamicResource FTC_ListItem}"
ItemsSource="{Binding ClientViewSource.View}"
SelectedItem="{Binding Path=Selection, Mode=TwoWay}"
/>
<ContentControl DataContext="{Binding Path=Selection, Mode=TwoWay}" >
<!--all the display stuff goes here for the detail view-->
</ContentControl>
</UserControl>
the following is the property in the viewmodel that the selecteditem of the listbox is bound to. It is also the binding for the content control that displays the details.
Public Property Selection As client
Get
Return Me._Selection
End Get
Set(ByVal value As client)
''capture current value of selection
_PreviousClient = _Selection
''If they are the same,
If value Is _PreviousClient Then
Return
End If
' Note that we actually change the value for now.This is necessary because WPF seems to query the
' value after the change. The list box likes to know that the value did change.
If Me._Selection.HasChanges = True And _Selection.HasErrors = False Then
'If HasChangesPrompt(value) = True Then
' ''user rejects saving changes, exit property
' Return
'End If
If FTCMessageBox.Show("Do you want to save your changes", "Unsaved Changes", MessageBoxButton.YesNo, MessageBoxImage.Warning) = MessageBoxResult.No Then
''SELECTION IS CANCELLED
' change the value back, but do so after the UI has finished it's current context operation.
Application.Current.Dispatcher.BeginInvoke(New Action(Sub()
'' revert the current selected item to its original values and reset its HasCHanges tracking
objHelper.CopyProperties(_OriginalClient, _Selection)
_Selection.HasChanges = False
RaisePropertyChanged(ClientSelectedPropertyName)
''continue with listbox selection changing to the new value for selection
_ClientCollectionViewSource.View.MoveCurrentTo(value)
End Sub), DispatcherPriority.Normal, Nothing)
Return
Else
''save changes to database
SaveExecute()
End If
End If
_Selection = value
_Selection.HasChanges = False
RaisePropertyChanged(ClientSelectedPropertyName)
''clone the unchanged version of the current selected client on na original variable
objHelper.CopyProperties(_Selection, _OriginalClient)
End Set
End Property
SO the idea is that if the user does not want to save changes, an original value of the client is copied (using reflection) over the current value, then the ui is updated and the selection continues on to the new value chosen by the user. However, like I said above, the listbox does not reflect this change even though I tired to hard code it with the following line:
''continue with listbox selection changing to the new value for selection
_ClientCollectionViewSource.View.MoveCurrentTo(value)
I got this solution by working customizing the solution posted HERE
can anyone help me figure out why my listbox goes out of sync when this happens.
Thanks in advance
First:
I can't find the real Problem in your solution, but you have definitly - and I repeat - definitly too much code and logic in your Property Setter. Try move it to other methods and validate your implementation of those many ´if else´ blocks.
Second:
The Setter gets only fired when you select a new Item in your Listbox, but you Raise a Property changes for ´ClientSelectedPropertyName´ and not for ´Selection´ as its supposed to be. Move the property changed alsways to the end of your setter.
Try this. I hope it helps :)
So I have a working example that I think follows the MVVM-Light standard. There is a lot going on so I will try to keep it short and precise.
I ended up using EventToCommand bound to the SelectionChanged event with a ListView(instead of listbox). The EventToCommand required new namespace references as is shown below. I then bound the EventToCommand to a RelayCommand in the view model which in turn calls a private sub that handles the client validation and saves/cancels/ and updates the listview seleceditem as required.
For further information, I have a navigation service that is used to navigat between views in my wpf application. I used the MVVM-Light messanger to send a navigationstarting message that is "recieved" by this view model. Then the same client validation functions are performed and naviagtion is canceled/allowed based on user response to the dialog message thrown. I will no include all of hte navigation code unless requested. The following is the code needed to solve my original question.
<UserControl x:Class="FTC.View.ClientListView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:FTC_Application"
xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
xmlns:cmd="http://www.galasoft.ch/mvvmlight"
mc:Ignorable="d"
d:DesignHeight="400" d:DesignWidth="900">
<ListView
Grid.Column="1"
Width="350"
Style="{DynamicResource FTC_ListView}"
ItemTemplate="{DynamicResource FTC_ClientListTemplate}"
ItemContainerStyle="{DynamicResource FTC_ListViewItem}"
ItemsSource="{Binding ClientViewSource.View}"
SelectedItem="{Binding Path=Selection, Mode=TwoWay}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<cmd:EventToCommand Command="{Binding SelectedItemChangedCommand}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</ListView>
<ContentControl DataContext="{Binding Path=Selection, Mode=TwoWay}" >
<!-- Display stuff and bound controls go here -->
</ContentControl>
</Grid>
</UserControl>
Then the following is the relevant code (I removed as much code as possible to keep it clear) in my view model:
Imports System.Data
Imports System.ComponentModel
Imports System.Collections.ObjectModel
Imports System.Windows.Threading
Imports GalaSoft.MvvmLight
Imports GalaSoft.MvvmLight.Command
Imports GalaSoft.MvvmLight.Messaging
Imports FTCModel
Imports FTC_Application.FTC.Model
Imports FTC_Application.FTC.View
Imports FTC_Application.FTC.ViewModel
Imports FTC_Application.FTC.MessageBox
Imports FTC_Application.FTC.Helpers
Imports FTC_Application.FTC.MessengerHelper
Namespace FTC.ViewModel
Public Class ClientListViewModel
Inherits ViewModelBase
Implements IDataErrorInfo
#Region "DECLARATIONS"
Public Const ClientCollectionPropertyName As String = "ClientCollection"
Public Const ClientSelectedPropertyName As String = "Selection"
Public Const ClientDetailCollectionPropertyName As String = "ClientDetailCollection"
Public Const ClientPropertyName As String = "Client"
''gets the data from LINQ to ENT Model
Private _Clients As New ObservableCollection(Of client)
''creats holder for the selected item two way binding
Private _Selection As New client
''the following is used to track changes for unding and canceling selection changed
Private _PreviousClient As New client
Private _PreviousOriginalClient As New client
Private _OriginalClient As New client
''Recieves observable collection and provicdes sorting and filtering function
Private _ClientCollectionViewSource As New CollectionViewSource
''RELAY COMMANDS declarations
Private _SaveCommand As RelayCommand
Private _SelectedItemChangedCommand As RelayCommand
''gets the VML for getting the data service
Private vml As ViewModelLocator = TryCast(Application.Current.Resources("Locator"), ViewModelLocator)
''this is a holder for the client data service
Private _ClientAccess As IClientDataService = vml.Client_Service
'' has functions using reflection for copying objects
Dim objHelper As New ObjectHelper
''tracks if client validation is coming from navigation or listview selecteditemchanged
Private bNavigatingFlag As Boolean = False
#End Region
#Region "PROPERTIES"
Public ReadOnly Property ClientViewSource As CollectionViewSource
Get
Return Me._ClientCollectionViewSource
End Get
End Property
Private Property Clients As ObservableCollection(Of client)
Get
Return Me._Clients
End Get
Set(ByVal value As ObservableCollection(Of client))
Me._Clients = value
_Clients = value
RaisePropertyChanged(ClientCollectionPropertyName)
End Set
End Property
Public Property Selection As client
Get
Return Me._Selection
End Get
Set(ByVal value As client)
''capture current value of selection
_PreviousClient = _Selection
objHelper.CopyProperties(_OriginalClient, _PreviousOriginalClient)
''If they are the same,
If value Is _PreviousClient Then
Return
End If
_Selection = value
_Selection.HasChanges = False
RaisePropertyChanged(ClientSelectedPropertyName)
''clone the unchanged version of the current selected client on na original variable
objHelper.CopyProperties(_Selection, _OriginalClient)
End Set
End Property
#End Region
#Region "COMMANDS"
Public ReadOnly Property SelectedItemChangedCommand() As RelayCommand
Get
If _SelectedItemChangedCommand Is Nothing Then
_SelectedItemChangedCommand = New RelayCommand(AddressOf SelectionChangedValidate)
End If
Return _SelectedItemChangedCommand
End Get
End Property
#End Region
#Region "METHODS"
Private Sub SelectionChangedValidate()
''Uses falg to tell if validation request triggered by navigation event or listview selecteditemchanged event
''use previous client for listview event and current client for navigating event
Dim _ClientToValidate As client
If bNavigatingFlag = True Then
_ClientToValidate = _Selection
Else
_ClientToValidate = _PreviousClient
End If
If _ClientToValidate.HasChanges = True And _ClientToValidate.HasErrors = False Then
Dim message = New DialogMessage(_ClientToValidate.chrCompany.ToString + " has been changed." + vbCrLf + "Do you want to save your changes?", AddressOf SavePreviousResponse) With { _
.Button = MessageBoxButton.YesNo, _
.Caption = "Unsaved Changes" _
}
Messenger.[Default].Send(message)
Exit Sub
End If
If _ClientToValidate.HasErrors = True Then
Dim message = New DialogMessage(_ClientToValidate.chrCompany.ToString + " has errors." + vbCrLf + "You must correct these errors before you can continue.", AddressOf HasErrorsResponse) With { _
.Button = MessageBoxButton.OK, _
.Caption = "Validation Error" _
}
Messenger.[Default].Send(message)
Exit Sub
End If
''reset the navigation flag
bNavigatingFlag = False
End Sub
Private Sub SavePreviousResponse(result As MessageBoxResult)
If result = MessageBoxResult.No Then
objHelper.CopyProperties(_PreviousOriginalClient, _PreviousClient)
_PreviousClient.HasChanges = False
Else
''user wants to save changes, save changes to database
SaveExecute()
End If
End Sub
Private Sub HasErrorsResponse(result As MessageBoxResult)
Selection = _PreviousClient
''_ClientCollectionViewSource.View.MoveCurrentTo(_PreviousClient)
End Sub
Private Function HasChangesPrompt(value As client) As Boolean
If FTCMessageBox.Show("Do you want to save your changes", "Unsaved Changes", MessageBoxButton.YesNo, MessageBoxImage.Warning) = MessageBoxResult.No Then
'' change the selected client back to its original value, but do so after the UI has finished its current context operation.
Application.Current.Dispatcher.BeginInvoke(New Action(Sub()
'' revert the current selected item to its original values and reset its HasCHanges tracking
objHelper.CopyProperties(_OriginalClient, _Selection)
_Selection.HasChanges = False
RaisePropertyChanged(ClientSelectedPropertyName)
''continue with listbox selection changing to the new value for selection
_ClientCollectionViewSource.View.MoveCurrentTo(value)
End Sub), DispatcherPriority.Normal, Nothing)
Return True
Else
''user wants to save changes, save changes to database
Return False
SaveExecute()
End If
End Function
#End Region
Public Sub New()
Clients = _ClientAccess.GetClient_All
''Sets the observable collection as the source of the CollectionViewSource
_ClientCollectionViewSource.Source = Clients
If Selection.idClient = 0 Then
Selection = Clients.Item(0)
End If
''register for messages
Messenger.[Default].Register(Of String)(Me, AddressOf HandleMessage)
End Sub
End Class
End Namespace
INXS, you will notice that the selection property setter has way less code/logic. Also, I think each part of the view model is testable and there is no direct coupling between my view and viewmodel. But this is my first WPF/MVVM application so I sitll don't fully grasp all the concepts.
I hope that this can help someone as it took my quite a while to figure it out.