I have a button on my Xaml page that its visibility is binded to a variable of Type : SYSTEM.Windows.Visibility in the view model, for the first time the page is loaded whether I set the variable to Hidden or Visible , it works fine. but aftre doing some operation when I change the variable to other status my GUI doesn't update.
Here are my xaml and MVVM
<Button Content="Extend" Name="btnExtend" Command="{Binding ExtendCommand}" Visibility="{Binding isVisible}" Grid.Row="2" Grid.Column="2" HorizontalAlignment="Right" Width="80" Margin="0,0,100,0" Height="25"/>
and view model :
Public Property isVisible As System.Windows.Visibility
Public Sub New()
isVisible = System.Windows.Visibility.Visible
End Sub
Public Sub diable()
isVisible = System.Windows.Visibility.Visible
End Sub
I read in some topics to change the variable to Boolean and use a BooleanToVisibilityConverter , I tried this too, but the result was the same.
I really don't get it what I do wrong.
your xaml code should be
<Button Content="Extend" Name="btnExtend" Command="{Binding ExtendCommand}" Visibility="{Binding isVisible,Mode=Twoway}" Grid.Row="2" Grid.Column="2" HorizontalAlignment="Right" Width="80" Margin="0,0,100,0" Height="25"/>
and your Viewmodel Code Should be
private Visibility _isVisible ;
public Visibility isVisible
{
get { return _isVisible ;}
set { _isVisible = value;RaisePropertyChanged("isVisible ");}
}
Check those links out:
http://msdn.microsoft.com/en-us/library/ms743695.aspx
http://www.daedtech.com/wpf-and-notifying-property-change
Tell your view that a property was changed by implementing INotifyPropertyChanged interface.
You need to fire a OnPropertyChanged() event in the setter of the Public Property to notify your changes to UI. Viewing your code, I seems that you are missing the OnPorpertyChanged() event implementation.
An another approach can be boolean values. Instead of make Visibility property, create a Boolean property and write a converter named "BooleanToVisibility" which will convert the value of "Visibility" Dependency Property.
Define Converter as a Static Resource in ResourceDictionary and then you can use it throughout the application. Converter approach is good to avoid rewriting show/hide logic in each view model.
Please let me know if you need working example on Converters.
Related
I have read many questions on this and so far I've not been able to find the answer on this apparently simple issue.
I have a view model, in which is a property. In my XAML I have a TextBox with a binding to that property.
But the property never seems to change.
Here's the textbox:
<TextBox Grid.Row="1"
Grid.Column="0"
Margin="4"
Text="{Binding CharNameFromTB}" />
And the relevant code behind for the ViewModel:
private String _charNameFromTB;
String CharNameFromTB
{
get { return _charNameFromTB; }
set
{
if (!string.Equals(this._charNameFromTB, value))
{
this._charNameFromTB = value;
RaisePropertyChanged("CharNameFromTB");
}
}
}
I have put a break point on the if statement in the setter, but it never triggers. Have I missed something obvious out? I tried setting the binding mode to twoway but that didn't change anything.
It's driving me a little mad. Any help would be appreciated!
You should make the property public in order to be able to bind to it:
private String _charNameFromTB;
public String CharNameFromTB
{
get { return _charNameFromTB; }
set
{
this._charNameFromTB = value;
RaisePropertyChanged("CharNameFromTB");
}
}
Also make sure that you have set the DataContext of the TextBox or any of its parent elements to an instance of your view model class where the CharNameFromTB property is defined.
Also note that by default, the source property is set when the TextBox loses focus.
If you want to update the source property on each keystroke you should set the UpdateSourceTrigger property of the Binding to PropertyChanged:
<TextBox Grid.Row="1"
Grid.Column="0"
Margin="4"
Text="{Binding CharNameFromTB, UpdateSourceTrigger=PropertyChanged}" />
I have a TabControl in an MVVM WPF application. It is defined as follows.
<TabControl Style="{StaticResource PortfolioSelectionTabControl}" SelectedItem="{Binding SelectedParameterTab}" >
<TabItem Header="Trades" Style="{StaticResource PortfolioSelectionTabItem}">
<ContentControl Margin="0,10,0,5" Name="NSDetailTradeRegion" cal:RegionManager.RegionName="NSDetailTradeRegion" />
</TabItem>
<TabItem Header="Ccy Rates" Style="{StaticResource PortfolioSelectionTabItem}">
<ContentControl Margin="0,10,0,5" Name="NSDetailCcyRegion" cal:RegionManager.RegionName="NSDetailCcyRegion" />
</TabItem>
<TabItem Header="Correlations / Shocks" Style="{StaticResource PortfolioSelectionTabItem}">
<ContentControl Name="NSDetailCorrelationRegion" cal:RegionManager.RegionName="NSDetailCorrelationRegion" />
</TabItem>
<TabItem Header="Facility Overrides" Style="{StaticResource PortfolioSelectionTabItem}" IsEnabled="False">
<ContentControl Name="NSDetailFacilityOverrides" cal:RegionManager.RegionName="NSDetailFacilityOverrides" />
</TabItem>
</TabControl>
So each tab item content has its own view associated with it. Each of those views has the MEF [Export] attribute and is associated with the relevant region through view discovery, so the above code is all I need to have the tab control load and switch between them. They all reference the same shared ViewModel object behind them and so all interact seamlessly.
My problem is that when the user navigates to the parent window, I want the tab control to default to the second tab item. That is easy enough to do when the window is first loaded, by specifying in XAML IsSelected="True" in TabItem number 2. It is less easy to do when the user navigates away from the screen and then comes back to it.
I thought about having a SelectedItem={Binding SelectedTabItem} property on the tab control, so I could programmatically set the selected tab in the ViewModel, but the problem is I have no knowledge of the TabItem objects in the ViewModel as they are declared above in the XAML only, so I have no TabItem object to pass to the setter property.
One idea I had was to make the child Views (that form the content of each of the tab items above) have a style on the UserControl level of their XAML, something along the following.
<Style TargetType={x:Type UserControl}>
<Style.Triggers>
<DataTrigger Property="IsSelected" Value="True">
<Setter Property="{ElementName={FindAncestor, Parent, typeof(TabItem)}, Path=IsSelected", Value="True" />
</DataTrigger>
</Style.Triggers>
</Style>
I know the findancestor bit isn't correct; I've just put it there to specify my intent, but I am not sure of the exact syntax. Basically for each UserControl to have a trigger that listens to a property on the ViewModel (not sure how I would distinguish each different UserControl as obviously they can't all listen to the same property or they would all select simultaneously when the property is set to True, but having a property for each usercontrol seems ugly) and then finds its parent TabItem container and sets the IsSelected value to true.
Am I on the right track with a solution here? Is it possible to do what I am pondering? Is there a tidier solution?
If you look at the TabControl Class page on MSDN, you'll find a property called SelectedIndex which is an int. Therefore, simply add an int property into your view model and Bind it to the TabControl.SelectedIndex property and then you can select whichever tab you like at any time from the view model:
<TabControl SelectedIndex="{Binding SelectedIndex}">
...
</TabControl>
UPDATE >>>
Setting a 'startup' tab is even easier using this method:
In view model:
private int selectedIndex = 2; // Set the field to whichever tab you want to start on
public int SelectedIndex { get; set; } // Implement INotifyPropertyChanged here
Just FYI,
I gone through the same issue where I add tabs dynamically using ObservableCollection source but last added Tab do not get selected.
I have done same changes what Sheridan said to select Tab as per SelectedIndex. Now last added Tab gets selected but it was not getting focused.
So to focus the Tab we have to add set Binding IsAsync property True.
<TabControl ItemsSource="{Binding Workspaces}" Margin="5" SelectedIndex="{Binding TabIndex, Mode=OneWay,UpdateSourceTrigger=PropertyChanged, IsAsync=True}">
The below code sample will create a dynamic tab using MVVM.
XAML
<TabControl Margin="20" x:Name="tabCategory"
ItemsSource="{Binding tabCategory}"
SelectedItem="{Binding SelectedCategory}">
<TabControl.ItemTemplate>
<DataTemplate>
<HeaderedContentControl Header="{Binding TabHeader}"/>
</DataTemplate>
</TabControl.ItemTemplate>
<TabControl.ContentTemplate>
<DataTemplate>
<ContentControl Content="{Binding TabContent}" />
</DataTemplate>
</TabControl.ContentTemplate>
</TabControl>
Modal Class
TabCategoryItem represents each tab item. On two properties, TabHeader will display a tab caption and TabContent contains the content/control to fill in each tab.
Public Class TabCategoryItem
Public Property TabHeader As String
Public Property TabContent As UIElement
End Class
VM Class
Public Class vmClass
Public Property tabCategory As ObjectModel.ObservableCollection(Of TabCategoryItem)
Public Property SelectedCategory As TabCategoryItem
End Class
The below code will fill and bind the content. I am creating two tabs, tab1 and tab2. Both tabs will contain text boxes. You can use any UIelement instead of text boxes.
Dim vm As New vmClass
vm.tabCategory = New ObjectModel.ObservableCollection(Of TabCategoryItem)
'VM.tabCategory colection will create all tabs
vm.tabCategory.Add(New TabCategoryItem() With {.TabHeader = "Tab1", .TabContent = new TextBlock().Text = "My first Tab control1"})
vm.tabCategory.Add(New TabCategoryItem() With {.TabHeader = "Tab2", .TabContent = new TextBlock().Text = "My first Tab control2"})
mywindow.DataContent = vm
The accepted answer is not working with DependencyObject on your ViewModel .
I'm using MVVM with DependencyObject and Just setting the TabControl didn't work for me.The problem I had was the the property was not getting update on the View when I was setting the tab selectedIndex from the ViewModel.
I did set the Mode to be two ways but nothing was working.
<TabControl SelectedIndex="{Binding SelectedTab,Mode=TwoWay}" >
...
</TabControl>
The ViewModel property "SelectedTab" was getting updated all the time when I navigated between tabs. This was confirming my binding was working properly. Each time I would navigate the tabs both the Get and Set would get called in my ViewModel. But if I try to set the SelectedIndex in the ViewModel it would not update the view.
ie: SelectedTab=0 or SelectedTab=1 etc...
When doing the set from the ViewModel the SelectedTab 'set' method would be called, but the view would never do the 'get'.
All I could find online was example using INotifyPropertyChanged but I do not wish to use that with my ViewModel.
I found the solutions in this page: http://blog.lexique-du-net.com/index.php?post/2010/02/24/DependencyProperties-or-INotifyPropertyChanged
With DependencyObject, you need to register the DependencyProperties. Not for all properties but I guess for a tabcontrol property you need to.
Below my code:
view.xaml
//Not sure below if I need to mention the TwoWay mode
<TabControl SelectedIndex="{Binding SelectedTab,Mode=TwoWay}" >
...
</TabControl>
ViewModel.cs
public class ViewModel : DependencyObject
{
public static readonly DependencyProperty SelectedTabDP = DependencyProperty.Register("SelectedTab", typeof(int), typeof(ViewModel));
public int SelectedTab
{
get { return (int)GetValue(SelectedTabDP); }
set { SetValue(SelectedTabDP, value); }
}
}
Basically all I had to do was to actually register the dependency property (DependencyProperty) as you can see above.
What made this hard to figure out was that I have a bunch of other Properties on that view and I didn't need to register them like that to make it work two ways. For some reason on the TabControl I had to register the property like I did above.
Hope this help someone else.
Turns out my problem were because my components have names:
x:Name="xxxxxxxx"
Giving names to components at the same time of biding them with DependencyObject seems to be the main cause of all my issues.
In order to improve semantic of my viewmodel and to not work with an int when using code to check for the selected tab, I made some additions to the accepted answer so to use an Enum instead of an int.
These are the steps:
Define an Enum representing the different tabs:
public enum RulesVisibilityMode {
Active,
History
}
Expose the SelectedTab as a property using the enum instead of the int:
public RulesVisibilityMode SelectedTab { get; set; }
Create a converter to convert from an int to your enum (I don't need the ConvertBack because I never select the active tab from the code, but you can add it too):
internal class RulesVisibilityModeConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException("Conversion from visibility mode to selected index has not been implemented");
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
int selectedTabIndex;
if (int.TryParse(value.ToString(), out selectedTabIndex))
{
return (RulesVisibilityMode)selectedTabIndex;
}
return null;
}
}
Bind the tabcontrol to the SelectedTab property through the converter:
<TabControl SelectedIndex="{Binding SelectedTab, Mode=OneWayToSource, Converter={StaticResource RulesVisibilityModeConverter}}" ...
Now every time you need to check for the selected tab in the code you deal with a readable enum:
if (this.SelectedTab != RulesVisibilityMode.Active) ...
I'm having some issues with binding some custom controls in a Windows Phone app right now. Usually this is never an issue but apparently my mind can't comprehend this today.
So I'm doing an MVVM style setup which is good. I have my page with a view and also a viewmodel. Now on a WebClient callback I assign the dataContext of my view to the list of models in my ViewModel, nice and simple thus far...now in my view I created a ListBox with a custom control in the datatemplate which is basically a cell in the list. I once again set my user controls dataContext to binding, and binding all the models values to the regular UI elements works no problem.
Here's a sample:
<Grid Grid.Column="0">
<Image Source="{Binding SmallPath}" VerticalAlignment="Top"/>
</Grid>
<Grid Grid.Column="1">
<StackPanel Margin="12,0,0,0">
<TextBlock x:Name="MemberId_TextBlock" Text="{Binding MemberId}" FontSize="28"
Margin="0,-8,0,0"
Foreground="{StaticResource PhoneForegroundBrush}"/>
<StackPanel Orientation="Horizontal" Margin="0,-11,0,0">
<TextBlock Text="{Binding DaysReported}" FontSize="42"
Margin="0,0,0,0"
Foreground="{StaticResource PhoneAccentBrush}"/>
<TextBlock Text="days" FontSize="24"
Margin="3,19,0,0"
Foreground="{StaticResource PhoneSubtleBrush}"/>
</StackPanel>
</StackPanel>
</Grid>
That's in my user control, and here's the the view where the usercontrol is housed:
<Grid x:Name="LayoutRoot" Background="Transparent">
<ListBox Name="TopSpotter_ListBox" ItemsSource="{Binding}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<!--<TextBlock Text="{Binding MemberId}"/>-->
<controls:TopSpotterItemControl DataContext="{Binding}"/>
<Grid Height="18"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
Now this is good enough but what I want to do in my view is set data from my model like Booleans that determine whether or not I should show certain Grids etc. So if I try to set a dependency property explicitly in my control it fires and will run logic in the Getter/Setters for instance. HOWEVER if I try to set these custom objects from a binding source it won't actually set.
Here's what works:
<controls:TopSpotterItemControl ChampVisibility="True">
This way will trigger the ChampVisibility property and then in the code behind of the user control I can set visibilities.
Here's what fails but I want to work:
<controls:TopSpotterItemControl ChampVisibility="{Binding IsChamp">
In addition I can still set the DataContext to {Binding} and the result will be unchanged.
In this scenario IsChamp is part of my model that I would like to bind to this user control which I guess comes from the dataContext being set on the view from the viewModel. I'm not sure what I can do to get this so the bindings work etc. without having to set custom properties.
Finally, here's my user control:
public partial class TopSpotterItemControl : UserControl
{
public string MemberId
{
get
{
return this.MemberId_TextBlock.Text;
}
set
{
this.MemberId_TextBlock.Text = value;
}
}
public bool ChampVisibility {
set
{
if (value)
{
this.Champ_Grid.Visibility = System.Windows.Visibility.Visible;
}
}
}
public static readonly DependencyProperty MemberNameProperty =
DependencyProperty.Register("MemberId", typeof(string), typeof(TopSpotterItemControl), new PropertyMetadata(null));
public static readonly DependencyProperty ChampVisibilityProperty =
DependencyProperty.Register("ChampVisibility", typeof(bool), typeof(TopSpotterItemControl), new PropertyMetadata(null));
public TopSpotterItemControl()
{
InitializeComponent();
}
}
Bit long winded and I hope I made things on the issue clear. My one major hang up so far, and I'd like to abstract as much control as I can to the user control via dependency properties explicitly set in xaml, rather than setting up binding in its xaml that depend on the knowledge of a model. Thanks!
Your DependencyProperty is badly formed. (I also don't see Champ_Grid defined in your class or XAML, but I assume that is an ommission)
Setting ChampVisibility = true in code works because it is unrelated to the DependencyProperty.
You can tell easily because the default value for your DP is invalid. It will compile, but the instance constructor will through an exception if it is ever invoked.
new PropertyMetadata(null)
bool = null = exception
If you call GetValue(TopSpotterItemControl.ChampVisibilityProperty) from somewhere you can confirm all of the above.
You should make changes to instance fields in the property changed handler and declare the property like the following, it will work:
Note that the property has to change (not just be set) for the event to be raised.
public bool ChampVisibility
{
get { return (bool)GetValue(ChampVisibilityProperty); }
set { SetValue(ChampVisibilityProperty, value); }
}
public static readonly DependencyProperty ChampVisibilityProperty =
DependencyProperty.Register("ChampVisibility ", typeof(bool), typeof(TopSpotterItemControl), new PropertyMetadata(true, (s, e) =>
{
TopSpotterItemControl instance = s as TopSpotterItemControl;
instance.Champ_Grid.Visibility = instance.ChampVisibility ? System.Windows.Visibility.Visible : System.Windows.Visibility.Collapsed;
}));
Incidentally, your MemberId DependencyProperty is also completely wrong and cannot work.
Note:
The Binding on your TextBox works, because it is binding to the DataContext (your model), so it probably shows the right value.
The Dependency property in your UserControl will never be set though.
Use the propdp code-snippet in Visual Studio so you dont have to concern yourself with the complexities of Dependency Property declaration.
Also check this out for more info about Dependency Properties
I've an WPF application where tried to implement MVVM pattern and Prism 2. I have a Usercontrol which has subscribed to an event fired from another Usercontrol. I would like to toggle visibility of few child elements in the subscribing control. Events are fired properly, even I am successfully able to bind data to some elements. How do I bind Visibility or any style property for that matter with the ViewModel and change them dynamically.
You can have a boolean property in your ViewModel and bind that property to the Visibility property of your controls. Since you will be asigning a boolean value and the Visibility property is expecting a Visibility enumeration value, you will have to use the BooleanToVisibilityConverter converter to make the conversion,
<Style.Resources>
<BooleanToVisibilityConverter x:Key="booleanToVisibilityConverter" />
</Style.Resources>
<Image Visibility="{Binding Path=ShowImage,
Converter={StaticResource booleanToVisibilityConverter}}"/>
Hope this helps.
Ezequiel Jadib
Although adding a Boolean property and using a value converter works, I would recommend adding a property of type Visibility to your ViewModel, e.g.
public Visibility ImageVisibility
{
get { return shouldShowImage ? Visibility.Visible : Visibility.Collapsed }
}
The advantage of this method is you don't need to write a converter for every property you want to express in a visual way (e.g. for a stock level that turns a label red when it drops below 10, you could have a converter you use once or just expose a StockLabelBrush property from your VM)
There's a simple solution for people who run into this issue.
In your view model, create a "Visibility" property like so:
public Visibility ShowModifyButtons
{
get { return (Visibility)GetValue(ShowModifyButtonsProperty); }
set { SetValue(ShowModifyButtonsProperty, value); }
}
public static readonly DependencyProperty ShowModifyButtonsProperty =
DependencyProperty.Register("ShowModifyButtons", typeof(Visibility), typeof(FileMatchViewModel),
new UIPropertyMetadata(Visibility.Collapsed));
In your XAML, bind to it like so:
<Button Focusable="False" Content="Save" Width="100" Margin="10" Visibility="{Binding ShowModifyButtons}"/>
Now, from your view model, you can set ShowModifyButtons to Visibility.Collapsed or Visibility.Visible as needed.
I understand that Silverlight 3.0 has binding but just want a simple example on how to use this to read a property from a class.
I have a class called Appointment which as a String property called Location:
Public Property Location() As String
Get
Return _Location
End Get
Set(ByVal Value As String)
_Location = Value
End Set
End Property
With a Private Declaration for the _Location as String of course.
I want a XAML element to bind to this property to display this in a TextElement, but it must be in XAML and not code, for example I want something like this:
<TextBlock Text="{Binding Appointment.Location}"/>
What do I need to do to get this to work?
It has to be a Silverlight 3.0 solution as some WPF features are not present such as DynamicResource which is what I'm used to using.
Just to add that my XAML is being loaded in from a seperate XAML File, this may be a factor in why the binding examples don't seem to work, as there are different XAML files the same Appointment.Location data needs to be applied.
You have two options.
If the "Appointment" class can be used as the DataContext for the control or Window, you can do:
<TextBlock Text="{Binding Location}" />
If, however, "Appointment" is a property of your current DataContext, you need a more complex path for the binding:
<TextBlock Text="{Binding Path=Appointment.Location}" />
Full details are documented in MSDN under the Binding Declarations page. If neither of these are working, make sure you have the DataContext set correctly.
You need something in code, unless you want to declare an instance of Appointment in a resource and bind to that but I doubt thats what you want.
You need to bind the Text property to the Property Path "Location" then assign the DataContext of the containing XAML to an instance of the Appointment:-
<Grid x:Name="LayoutRoot" Background="White">
<TextBlock Text="{Binding Location}" />
</Grid>
Then in the control's load event:-
void Page_Loaded(object sender, RoutedEventArgs e)
{
this.DataContext = new Appointment() { Location = "SomePlace" };
}
Note in this case I'm using the default Page control.
If I'm reading correctly, you need to create an instance of Appointment, set the DataContext of the control to that instance and modify your binding to just say: Text="{Binding Location}"
Also, consider implementing INotifyPropertyChanged on your Appointment class to allow the data classes to notify the UI of property value changes.