1) Using MVVM Light, I have an xCeed datagrid which I only want visible only after the user has opened a file.
So I've created a boolean property in the ViewModel and use the booleantoVisibilityConverter to parse that property
<Window.Resources>
<BooleanToVisibilityConverter x:Key="booleanToVisibilityConverter" />
So in the (lengthy so I'm cutting off the beginning it) xaml I put on the datagrid, I added this to the end:
Visibility="{Binding Path=FileOpened, Converter={StaticResource booleanToVisibilityConverter}}">
The moment I put that to use though, the grid disappears from the designtime view, which I do not want.
Checking to see if I'm in Design View inside the property's accessor doesn't seem to help.
public bool FileOpened
{
get
{
if (IsInDesignMode)
return true;
return fileOpened;
}
set => fileOpened = value;
}
EDIT: I've also tried to call RaisePropertyChanged on the mutator. Didn't expect it to help and, sure enough, it didn't.
Related
OK this is an interesting one.
I have a wpf application with tabs. What I want to do is have a DB setting that turns off the ability to edit all textboxs. What I was thinking was to bring in the value, if the value is true then I would turn all the text boxes to read only.
I have seen this example:
private void DisableControls(Control con)
{
foreach (Control c in controls)
{
DisableControls(c);
}
con.Enabled = false;
}
However I get red squiggly line under controls and again under Enabled. I will preface this by saying I am new to WPF.
Does anyone have a solution to this (or even a better way) any pointing in the right way would help.
Create a view model that wraps your database models
public class MyViewModel : INotifyPropertyChanged
{
public bool MakeReadOnly {get;set;}
}
Reference your view model in the View
<Window x:Class="Example.MainWindow"
...
xmlns:local="clr-namespace:Example"
...>
<Window.Resources>
<local:MyViewModel x:Key="ViewModel"/>
</Window.Resources>
...
</Window>
Bind the boolean value to your textboxes IsReadOnly property
<TextBox x:Name="FirstName" IsReadOnly="{Binding MakeReadOnly">
The user may not modify the contents of this TextBox if marked as readonly
</TextBox>
<TextBox x:Name="LastName" IsReadOnly="{Binding MakeReadOnly">
The user may not modify the contents of this TextBox if marked as readonly
</TextBox>
More on View Models here
Hope this helps!
I have a serious issue with binding any command to my user control. Everything compiles, but the command is never called. I have tried two approaches - first, I tried to bind the command to a button inside my control, and when I was unable to do it, I tried to bind the command to an inputcommand of the control itself to see if it would work. It didn't. The control itself is within an ItemsControl, in case that matters.
Here's a simplified version of what I did. In the xaml.cs file of the control:
public static readonly DependencyProperty CloseCommandProperty = DependencyProperty.Register(
"CloseCommand",
typeof(ICommand),
typeof(Thumbnail),
new UIPropertyMetadata(null)
);
public ICommand CloseCommand
{
get { return (ICommand)GetValue(CloseCommandProperty); }
set { SetValue(CloseCommandProperty, value); }
}
In the UserControl's xaml file, the offending button (the UserControl has Name="Control", and Hash is another dependency property):
<Button Command="{Binding ElementName=Control, Path=CloseCommand}" CommandParameter="{Binding ElementName=Control, Path=Hash}">
<TextBlock Text="X"/></Button>
Now, a simplified (irrelevant properties not included) datatemplate part of the xaml file of the view (which has a datacontext, if that matters), where I use this control:
<ItemsControl.ItemTemplate>
<DataTemplate>
<local:Thumbnail Hash="{Binding Hash}"
CloseCommand="{Binding ElementName=Control, Path=DataContext.RemoveImageCommand}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
Just for the sake of completeness, I'll include the command from the viewmodel.
private bool CanRemoveImageCommandExecute(string hash)
{
return true;
}
private void RemoveImageCommandExecute(string hash)
{
MessageBox.Show("ABC","ABC");
}
public ICommand RemoveImageCommand
{
get { return new RelayCommand<string>(RemoveImageCommandExecute, CanRemoveImageCommandExecute);}
}
The RelayCommand class comes from MicroMVVM, and it just creates a command from two functions (and works everywhere else).
Can you tell me why clicking the button does nothing and how to fix it?
It seems that, even though I wasted a few hours on that, I was too quick to ask the question. Literally a few minutes after posting it, I realized that my binding in ItemTemplate is wrong.
The problem was that I used ElementName instead of RelativeSource:
CloseCommand="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=local:AddImage}
Where local:AddImage is the name of the view which has the DataContext set to the viewmodel..
I basically want to take a bunch of names in a collection and bind them to a combobox. For example:
Bill
Jack
Bob
Kevin
and have those items in a collection and have it bound to the ComboBox. I'm not sure if the list will be updated dynamically or not, but I prefer to plan for it to be. Any help would be appreciated. I've been trying for a few hours now and can't figure it out. I want to do it in XAML and not the code-behind. In the code-behind,
MyComboBox.ItemsSource = MyObservableCollection;
works fine. I don't know how to do that in XAML though with the collection declared in the code-behind.
Thanks in advance (again), community.
*EDIT:
This is how I have the collection declared and accessible.
public ObservableCollection<string> propertynames
{
get {return _propertynames;}
}
private ObservableCollection<string> _propertynames;
The last thing I tried was this:
<Window.Resources>
<CollectionViewSource Source="{Binding propertynames}" x:Key="srcSort"/>
</Window.Resources>
....
<ComboBox x:Name="cboSort" HorizontalAlignment="Left" VerticalAlignment="Top"
Width="256" Background="WhiteSmoke" Margin="12,50,0,0" FontSize="12pt"
Height="27.28"
SelectedIndex="0"
SelectionChanged="cboWorkCenters_SelectionChanged"
ItemsSource="{Binding Path = {StaticResource srcSort}}">
</ComboBox>
....
I'm a total n00b to this stuff. Been in it about a week now, so I may have done something really obvious to a seasoned user.
*EDIT #2
<Window x:Class="WpfApplication1.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:s="clr-namespace:WpfApplication1"
Title="Window1" Height="226" Width="242"
DataContext="{Binding RelativeSource={RelativeSource Self}}">
<Grid>
<ComboBox Margin="43,71,40,77"
Name="comboBox1"
ItemsSource="{Binding ob}" />
</Grid>
</Window>
namespace WpfApplication1
{
/// <summary>
/// Interaction logic for Window1.xaml
/// </summary>
public partial class Window1 : Window
{
public ObservableCollection<string> ob
{
get
{
return _ob;
}
}
private ObservableCollection<string> _ob = new ObservableCollection<string>();
public Window1()
{
InitializeComponent();
FillObj();
//comboBox1.ItemsSource = ob;
}
private void FillObj()
{
for (int i = 1; i < 6; i++)
{
_ob.Add(i.ToString());
}
}
}
}
Made above real simple project just to see if I was doing it all wrong. This worked fine so something else must be causing it to fail.
*EDIT #3
*PROBLEM FIXED
For God's sake, I figured it out. I've been on this for HOURS and it's just silly what's caused it to fail.
The solution is this: I wasn't instantiating _propertynames when I declared it. I was querying the class properties with Linq to get the list of properties and then created _propertynames by passing ...GetProperties.ToList<...>() to the constructor. Apparently, you have to instantiate the variable so it hits during InitializeComponent. Unreal.
Once I did that and then added the items to it after the fact, it worked fine.
I wish WPF had a face so I could punch it. I know it's my ignorance of how it works, but I really could have used some kind of message.
Thanks guys for the help. Both of your suggestions were useful once I took care of the root issue.
private ObservableCollection<string> _propertynames
needs to be
private ObservableCollection<string> _propertynames = new ObservableCollection<string>()
There are countless ways of doing this. Once you've created the collection in code-behind, you can:
Call Resources.Add to add it to the window's resource dictionary, and then bind to the resource, e.g. ItemsSource="{Binding {DynamicResource MyList}}".
Give the ComboBox a name (using the x:Name attribute) and set its ItemsSource explicitly in code, e.g. MyComboBox.ItemsSource = myCollection;.
Create a class, make the collection a property of the class, and set the window's DataContext to an instance of that class and bind to it directly, e.g. ItemsSource = "{Binding MyCollectionProperty}".
Make the collection a property of the window, set the window's DataContext to this, and bind to the property (this is essentially the same technique as #3, only you're not creating a new class).
Without setting the window's DataContext, you can still reference a property on it using binding as long as you've given it a name, e.g. {Binding ElementName=MyWindow, Path=MyCollection}. (This is the same as Ross's suggestion.)
Or, without giving the window a name, you can use RelativeSource binding to find the ancestor Window and bind to a property on it. I don't have any confidence in my ability to write a working binding expression that uses RelativeSource off the top of my head, so I'll leave that as an exercise for the reader.
You can set the DataContext of the ComboBox to the instance of your collection, and then set itsItemsSource to {Binding}. You probably wouldn't do this in practice; I mention it just because it seems to be a common mistake for people to set the DataContext of a control without also setting a binding, and then wonder why content from the bound object isn't showing up.
(While I've said "window" in the above, everything I've said is also true for user controls.)
I'm sure there are at least five other ways to do this that I'm not thinking of. Binding is really, really flexible.
What have you tried so far?
I would approach it as follows, assuming the combo box is within a UserControl with a code-behind class containing the public property MyObservableCollection:
<UserControl x:Name="MyCollectionOwnerControl">
<ComboBox ItemsSource="{Binding ElementName=MyCollectionOwnerControl, Path=MyObservableCollection, Mode=OneWay}" />
</UserControl>
I am trying to figure out the best way to select all the text in a TextBox the first time the control is loaded. I am using the MVVM pattern, so I am using two-way binding for the Text property of the TextBox to a string on my ViewModel. I am using this TextBox to "rename" something that already has a name, so I would like to select the old name when the control loads so it can easily be deleted and renamed. The initial text (old name) is populated by setting it in my ViewModel, and it is then reflected in the TextBox after the data binding completes.
What I would really like to do is something like this:
<TextBox x:Name="NameTextBox" Text="{Binding NameViewModelProperty, Mode=TwoWay}" SelectedText="{Binding NameViewModelProperty, Mode=OneTime}" />
Basically just use the entire text as the SelectedText with OneTime binding. However, that does not work since the SelectedText is not a DependencyProperty.
I am not completely against adding the selection code in the code-behind of my view, but my problem in that case is determining when the initial text binding has completed. The TextBox always starts empty, so it can not be done in the constructor. The TextChanged event only seems to fire when a user enters new text, not when the text is changed from the initial binding of the ViewModel.
Any ideas are greatly appreciated!
Dan,
I wrote a very simple derived class, TextBoxEx, that offers this functionality. The TextBoxEx class derives from TextBox, and can be referenced in XAML for any and all of your TextBox’s. There are no methods to call. It just listens for Focus events and selects it own text. Very simple.
Usage is as follows:
In XAML, reference the assembly where you implement the TextBoxEx class listed below, and add as many TextBoxEx elements as you need. The example below uses data binding to display a username.
<UserControl x:Class="MyApp.MainPage"
xmlns="http://schemas.microsoft.com/client/2007"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:c="clr-namespace:ClassLibrary;assembly=ClassLibrary"
>
.
.
.
<c:TextBoxEx x:Name="NameTextBox" Text="{Binding NameViewModelProperty, Mode=TwoWay}" Width="120" />
This code below works with Silverlight 3.
using System.Windows;
using System.Windows.Controls;
namespace ClassLibrary
{
// This TextBox derived class selects all text when it receives focus
public class TextBoxEx : TextBox
{
public TextBoxEx()
{
base.GotFocus += OnGotFocus;
}
private void OnGotFocus(object sender, RoutedEventArgs e)
{
base.SelectAll();
}
}
}
Good luck.
I'm leaving Jim's solution as the answer, since calling SelectAll() on the GotFocus event of the TextBox did the trick.
I actually ended up making a Blend TriggerAction and an EventTrigger to do this instead of subclassing the TextBox or doing it in code-behind. It was really simple to do and nice to be able to keep the behavior logic encapsulated and just add it declaratively in XAML to an existing TextBox.
Just posting this in case anyone else comes across this thread and is interested:
XAML:
<TextBox x:Name="NameTextBox" Text="{Binding NameViewModelProperty, Mode=TwoWay}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="GotFocus">
<local:SelectAllAction/>
</i:EventTrigger>
</i:Interaction.Triggers>
</TextBox>
C#
public class SelectAllAction : TriggerAction<TextBox>
{
protected override void Invoke(object parameter)
{
if (this.AssociatedObject != null)
{
this.AssociatedObject.SelectAll();
}
}
}
Just wanna add a link I found pertaining to this - here is a fantastic discussion (read comments) on Behaviours vs subclassing vvs attached properties...
This is MVVM application. There is a window and related view model class.
There is TextBox, Button and ListBox on form. Button is bound to DelegateCommand that has CanExecute function. Idea is that user enters some data in text box, presses button and data is appended to list box.
I would like to enable command (and button) when user enters correct data in TextBox. Things work like this now:
CanExecute() method contains code that checks if data in property bound to text box is correct.
Text box is bound to property in view model
UpdateSourceTrigger is set to PropertyChanged and property in view model is updated after each key user presses.
Problem is that CanExecute() does not fire when user enters data in text box. It doesn't fire even when text box lose focus.
How could I make this work?
Edit:
Re Yanko's comment:
Delegate command is implemented in MVVM toolkit template and when you create new MVVM project, there is Delegate command in solution. As much as I saw in Prism videos this should be the same class (or at least very similar).
Here is XAML snippet:
...
<UserControl.Resources>
<views:CommandReference x:Key="AddObjectCommandReference"
Command="{Binding AddObjectCommand}" />
</UserControl.Resources>
...
<TextBox Text="{Binding ObjectName, UpdateSourceTrigger=PropertyChanged}"> </TextBox>
<Button Command="{StaticResource AddObjectCommandReference}">Add</Button>
...
View model:
// Property bound to textbox
public string ObjectName
{
get { return objectName; }
set {
objectName = value;
OnPropertyChanged("ObjectName");
}
}
// Command bound to button
public ICommand AddObjectCommand
{
get
{
if (addObjectCommand == null)
{
addObjectCommand = new DelegateCommand(AddObject, CanAddObject);
}
return addObjectCommand;
}
}
private void AddObject()
{
if (ObjectName == null || ObjectName.Length == 0)
return;
objectNames.AddSourceFile(ObjectName);
OnPropertyChanged("ObjectNames"); // refresh listbox
}
private bool CanAddObject()
{
return ObjectName != null && ObjectName.Length > 0;
}
As I wrote in the first part of question, following things work:
property setter for ObjectName is triggered on every keypress in textbox
if I put return true; in CanAddObject(), command is active (button to)
It looks to me that binding is correct.
Thing that I don't know is how to make CanExecute() fire in setter of ObjectName property from above code.
Re Ben's and Abe's answers:
CanExecuteChanged() is event handler and compiler complains:
The event
'System.Windows.Input.ICommand.CanExecuteChanged'
can only appear on the left hand side
of += or -=
there are only two more members of ICommand: Execute() and CanExecute()
Do you have some example that shows how can I make command call CanExecute().
I found command manager helper class in DelegateCommand.cs and I'll look into it, maybe there is some mechanism that could help.
Anyway, idea that in order to activate command based on user input, one needs to "nudge" command object in property setter code looks clumsy. It will introduce dependencies and one of big points of MVVM is reducing them.
Edit 2:
I tried to activate CanExecute by calling addObjectCommand.RaiseCanExecuteChanged() to ObjectName property setter from above code. This does not help either. CanExecute() is fired few times when form is initialized, but after that it never gets executed again. This is the code:
// Property bound to textbox
public string ObjectName
{
get { return objectName; }
set {
objectName = value;
addObjectCommand.RaiseCanExecuteChanged();
OnPropertyChanged("ObjectName");
}
}
Edit 3: Solution
As Yanko Yankov and JerKimball wrote, problem is static resource. When I changed button binding like Yanko suggested:
<Button Command="{Binding AddObjectCommand}">Add</Button>
things started to work immediately. I don't even need RaiseCanExecuteChanged(). Now CanExecute fires automatically.
Why did I use static resource in first place?
Original code was from WPF MVVM toolkit manual. Example in that manual defines commands as static resource and then binds it to menu item. Difference is that instead of string property in my example, MVVM manual works with ObservableCollection.
Edit 4: Final explanation
I finally got it. All I needed to do was to read comment in CommandReference class. It says:
/// <summary>
/// This class facilitates associating a key binding in XAML markup to a command
/// defined in a View Model by exposing a Command dependency property.
/// The class derives from Freezable to work around a limitation in WPF when
/// databinding from XAML.
/// </summary>
So, CommandReference is used for KeyBinding, it is not for binding in visual elements. In above code, command references defined in resources would work for KeyBinding, which I don't have on this user control.
Of course, sample code that came with WPF MVVM toolkit were correct, but I misread it and used CommandReference in visual elements binding.
This WPF MVVM really is tricky sometimes.
Things look much clearer now with the edits, thanks! This might be a stupid question (I'm somewhat tired of a long day's work), but why don't you bind to the command directly, instead of through a static resource?
<Button Command="{Binding AddObjectCommand}">Add</Button>
Since you are using the DelegateCommand, you can call it's RaiseCanExecuteChanged method when your text property changes. I'm not sure what you are trying to accomplish with your CommandReference resource, but typically you just bind the commands directly to the button element's Command property:
<TextBox Text="{Binding ObjectName, UpdateSourceTrigger=ValueChanged}" />
<Button Command="{Binding AddObjectCommand}" Content="Add" />
This would be the relevant portion of your view model:
public string ObjectName
{
get { return objectName; }
set
{
if (value == objectName) return;
value = objectName;
AddObjectCommand.RaiseCanExecuteChanged();
OnPropertyChanged("ObjectName");
}
}
Try raising CanExecuteChanged when your property changes. The command binding is really distinct from the property binding and buttons bound to commands are alerted to a change in status by the CanExecuteChanged event.
In your case, you could fire a check when you do the PropertyChanged on the bound property that would evaluate it and set the command's internal CanExecute flag and then raise CanExecuteChanged. More of a "push" into the ICommand object than a "pull".
Echoing Abe here, but the "right" path to take here is using:
public void RaiseCanExecuteChanged();
exposed on DelegateCommand. As far as dependencies go, I don't think you're really doing anything "bad" by raising this when the property that the command depends on changes within the ViewModel. In that case, the coupling is more or less contained wholly within the ViewModel.
So, taking your above example, in your setter for "ObjectName", you would call RaiseCanExecuteChanged on the command "AddObjectCommand".
I know this is an old question but I personally think it's easier to bind the textbox Length to button's IsEnabled property, e.g.:
<TextBox Name="txtbox" Width="100" Height="30"/>
<Button Content="SomeButton " Width="100" Height="30"
IsEnabled="{Binding ElementName=txtbox, Path=Text.Length, Mode=OneWay}"></Button>
If ElementName binding does not work, use:
<Entry x:Name="Number1" Text="{Binding Number1Text}" Keyboard="Numeric"></Entry>
<Entry x:Name="Number2" Text="{Binding Number2Text}" Keyboard="Numeric"></Entry>
<Button Text="Calculate" x:Name="btnCalculate" Command="{Binding CalculateCommand}" IsEnabled="{Binding Source={x:Reference Number1, Number2}, Path=Text.Length, Mode=OneWay}"></Button>
or use:
<Entry x:Name="Number1" Text="{Binding Number1Text}" Placeholder="Number 1" Keyboard="Numeric"></Entry>
<Entry x:Name="Number2" Text="{Binding Number2Text}" Placeholder="Number 2" Keyboard="Numeric"></Entry>
<Button VerticalOptions="Center" Text="Calculate" x:Name="btnCalculate" Command="{Binding CalculateCommand}">
<Button.Triggers>
<DataTrigger TargetType="Button"
Binding="{Binding Source={x:Reference Number1, Number2},
Path=Text.Length}"
Value="{x:Null}">
<Setter Property="IsEnabled" Value="False" />
</DataTrigger>
</Button.Triggers>