Develop Reference

Cant select value from combobox

I cant seem to select a value from a combobox. I've looked at the other questions/solutions, but none of the answers, nor questions, seems to be relevant to my problem.
In my view :
ComboBox Grid.Column="1" ItemsSource="{Binding Path=FileInstructions, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged }"
SelectedItem="{Binding Path=SelectedFileInstruction, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
In my viewModel:
public FileInstructionSelectorControl(Action<FileInstruction> selectionChangedEvent)
{
InitializeComponent();
DataContext = this;
//_selectionChangedEvent = selectionChangedEvent;
SetFileInstructions();
/*var myList = new List<string>() { "Bob" };
FileInstructions = new ObservableCollection<string>(myList);*/
SelectedFileInstruction = FileInstructions[0];
}
private void SetFileInstructions()
{
var instructions = Enum.GetValues(typeof(FileInstruction)).Cast<FileInstruction>();
FileInstructions = new ObservableCollection<string>(instructions.Select(item => item.ToString()).ToList());
}
public event PropertyChangedEventHandler PropertyChanged;
private ObservableCollection<string> _fileInstructions;
public ObservableCollection<string> FileInstructions
{
get => _fileInstructions;
set
{
_fileInstructions = value;
OnPropertyChanged(nameof(FileInstructions));
}
}
private string _selectedFileInstruction;
public string SelectedFileInstruction
{
get => _selectedFileInstruction;
set
{
_selectedFileInstruction = value;
OnPropertyChanged(nameof(SelectedFileInstruction));
SelectionChanged();
}
}
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
public void SelectionChanged()
{
//_selectionChangedEvent(SelectedFileInstruction);
}
As you can see, I've tried manually setting the selectedItem to the first item in the list, and it displays correctly
But I'm unable to select a new value from the comboBox. The list does populate, but it feels like the comboBox is locked/disabled, as I unable to get a drop-down when clicking the comboBox.
Edit :
I'm able to tab to the combo-box, and change the values with my keyboard, but not able to get the combobox to drop down with my mouse.

This issue isn't related to binding, but what appears to be hardware related, as per this question

C# How to edit cell value in gridview?

I have a gridview shown as below in XAML
<ListView x:Name="listTasks">
<ListView.View>
<GridView x:Name="gridTasks">
<GridViewColumn Header="ID" HeaderStringFormat="Lowercase" Width ="26" DisplayMemberBinding="{Binding id}"/>
<GridViewColumn Header="Something" Width="113" DisplayMemberBinding="{Binding something}"/>
<GridViewColumn Header="State" Width="179" DisplayMemberBinding="{Binding currentState}"/>
</GridView>
</ListView.View>
</ListView>
and i have a button which adds to this gridview using the below
m.myList.Add(new mylistview.myitems
{
id = m.id,
something= m.something,
currentState = m.currentState,
});
This button works perfectly by adding the row into the gridview. However I would like to modify theCurrentState using a method that is running. How would I locate for example, ID = "8" and then modify theCurrentState for that row?
UPDATED CODE SHOWN
I've now replaced my list<Task> with ObservableCollection and managed to get it to add to my listview when I click onto my button. However, I am struggling to implement the iNotifyPropertyChanged into my code and getting it to work correctly... Below is my listview class
public class mylistview : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged([System.Runtime.CompilerServices.CallerMemberName] string propertyName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
private string _currentState;
public string currentState
{
get { return _currentState; }
set
{
_currentState = value;
OnPropertyChanged();
}
}
public ObservableCollection<myitems> _myList = new ObservableCollection<myitems>();
public ObservableCollection<myitems> myList
{
get { return _myList; }
}
private static int _id = 0;
public class myitems
{
public int id { get; set; }
public string something{ get; set; }
public string currentState { get; set; }
}
public int id
{
get { return _id; }
set { _id = value; }
}
}

So I see you're using data bindings already, that's good. But your question makes me think you haven't quite grasped everything it can do for you yet.
My recommendation would be to forget about adding items directly to listOfTasks.Items. Instead you should make an ObservableCollection to hold that list and bind the listOfTasks to it. Like so:
ObservableCollection tasks = new ObservableCollection<mylistview.myitems>();
ListOfTasks.ItemsSource = tasks;
With that binding in place you should be able to simply add new items to the tasks list when they click your button:
tasks.Add(new mylistview.myitems
{
id = theId,
something= something,
currentState = theCurrentState,
});
and it should automatically update the GUI.
The last step is to make sure that the class mylistview.myitems implements INotifyPropertyChanged. This is easier than it sounds; you just need to have it trigger an event any time the property is set. Something like so:
public class exampleProperties: INotifyPropertyChanged
{
//this is the event you have to emit
public event PropertyChangedEventHandler PropertyChanged;
//This is a convenience function to trigger the event.
//The CallerMemberName part will automatically figure out
//the name of the property you called from if propertyName == ""
protected void OnPropertyChanged([System.Runtime.CompilerServices.CallerMemberName] string propertyName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName);
}
}
//Any time this property is set it will trigger the event
private string _currentState = "";
public string currentState
{
get { return _currentState; }
set
{
if (_currentState != value)
{
_currentState = value;
OnPropertyChanged();
}
}
}
}
Now that the gridview is bound to an ObservableCollection and the items held in that collection can notify interested GUI controls that their properties have changed, you should simply be able to update the GUI simply by changing the appropriate item in the collection.
And here's an example of a form that uses the whole technique: https://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged(v=vs.110).asp
edit
I forgot that you specifically need to bind to the ItemSource property of the ListView. The way I have done it in the past is to set ItemsSource={binding} in the ListView's xaml and then assign an ObservableCollection to ListView.DataContext. However I have found an easier way and updated the original post with it. Here's a reference: http://www.wpf-tutorial.com/listview-control/listview-with-gridview/
Edit 2
Aha, you're adding the iPropertyChangedNotify to the wrong thing. It goes on the myitems class like so:
public class myitems : iNotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged([System.Runtime.CompilerServices.CallerMemberName] string propertyName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
private int _id;
public int id
{
get { return _id; }
set
{
_id = value;
OnPropertyChanged();
}
}
public string something{ get; set; }
public string currentState { get; set; }
}
I leave updating the current state and something properties as an excersize. They also need to trigger the OnPropertyChanged event when their value is set.

Maybe with
listOfTasks.Items.Cast<ListViewItem>().First(item => item.ID == "8").theCurrentState = newState;
//I'm not sure about the Cast stuff, because I don't know what types the ListView uses for its items
Of course you could iterate through the items with a loop and check manually for the ID as well.

Image Binding Not Working on Reload Window

I have an Image element that's bound to an ImageSource element inside a class that I've created. The ImageSource gets updated every time a slider is changed. When I first instantiate my window, the ImageSource is blank until the user loads a file. Once the file is loaded, the image appears and the user can scroll the slider and see the image change. They can then select "OK" on the dialog to save this pattern. This all works fine.
However, if they double-click on the item in the ListView then it will re-open this dialog to make further edits. So, it creates a new dialog and then reloads the pertinent info about the image. However, for whatever reason... the image binding no longer works. I can put a breakpoint on the ImageSource getter and everytime I change the slider, the image does get updated... However, it just doesn't appear the be binding correctly. Why would it bind correctly on the first time the window is opened, but not on subsequent openings. I'll try to lay out my code.
In my .XAML code:
<UserControl x:Class="MyControls.CreatePattern"
x:Name="PatternCreation"
...
d:DesignHeight="160" d:DesignWidth="350">
<Slider Value="{Binding ElementName=PatternCreation, Path=Pattern.ZNorm, Mode=TwoWay}" Maximum="1" Name="Slider" VerticalAlignment="Stretch" />
<Image Name="PatternPreview" Source="{Binding ElementName=PatternCreation, Path=Pattern.WPFSlice}" Stretch="Uniform"></Image>
</UserControl
In my code behind I define the Pattern to be bound:
protected PatternVoxelBased mPattern = new PatternVoxelBased();
public PatternVoxelBased Pattern
{
get { return mPattern ; }
set { mPattern = value; }
}
In my PatternVoxelBased class, I have a WPFSlice and ZNorm properties defined like this:
protected ImageSource mWPFSlice;
public ImageSource WPFSlice
{
get { return mWPFSlice; }
set
{
mWPFSlice = value;
NotifyPropertyChanged("WPFSlice");
}
}
protected double mZNorm = 0.5;
public double ZNorm
{
get { return mZNorm; }
set
{
if (mZNorm == value) return;
mZNorm = value;
NotifyPropertyChanged("ZNorm");
WPFSlice = BuildImageAtZ(mZNorm);
}
}
I have an event to load the dialog window the first time:
private void CreatePattern_Click(object sender, RoutedEventArgs e)
{
CCreateVoxelPattern dlg = new CCreateVoxelPattern();
dlg.DataContext = DataContext;
dlg.CShow(PatternLibraryMenu);
}
My ListView Double-Click function to reload the dialog window:
private void ListViewPatternLibrary_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
PatternVoxelBased item = ((ListView)sender).SelectedValue as PatternVoxelBased;
CCreateVoxelPattern dlg = new CCreateVoxelPattern();
dlg.DataContext = DataContext;
dlg.Main.Pattern = item;
dlg.Main.LoadPattern();
dlg.CShow(PatternLibraryMenu);
}
public void LoadPattern()
{
if (Pattern == null) return;
Pattern.WPFSlice = Pattern.BuildImageAtZ(Pattern.ZNorm);
}

In your class where this is
protected PatternVoxelBased mPattern = new PatternVoxelBased();
public PatternVoxelBased Pattern
{
get { return mPattern ; }
set { mPattern = value; }
}
you have to implement INotifyPropertyChanged.
Example
public class YourClass: INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(PropertyChangedEventArgs e)
{
if (PropertyChanged != null)
{
PropertyChanged(this, e);
}
}
protected PatternVoxelBased mPattern = new PatternVoxelBased();
public PatternVoxelBased Pattern
{
get { return mPattern ; }
set { mPattern = value; OnPropertyChanged(new PropertyChangedEventArgs("Pattern"));}
}
}
EDIT
In your Pattern-class, you have to implement that too on every Property.

Binding image to embedded resource in wpf

I'm new to WPF, and I'm encountering a problem. I have a ListBox with images arranged in a floorplan, the image source is bound to a uri in the code. uri is to an embedded resource in the project. This all works fine on startup, until I have to change an image. No exceptions, but the images do not change. When I run in debug, I can see that even though the ObservableCollection items change, the mainwindow images do not.
Is this due to caching, or is it something else? I try to disable caching in the xaml, but I get the error The TypeConverter for "CacheMode" does not support converting from a string.
I'll do my best to be brief with the code and only include relevant information:
public partial class MainWindow : Window, INotifyPropertyChanged
{
public ObservableCollection<ComputerInfo> CompListObs;
public ObservableCollection<ComputerInfo> compListObsNotifier
{
get { return CompListObs; }
set
{
CompListObs = value;
RaisePropertyChanged("compListObsNotifier");
}
}
//...
public MainWindow()
{
InitializeComponent();
this.DataContext = this;
// This correctly loads the images from the xml and displays them on the main window:
var items = XDocument.Load(#"path to xml")
.Descendants("Computer")
.Select(i => new ComputerInfo {
MachineName = (string)i.Element("MachineName"),
Lat = (double)i.Element("Long"),
Lon = (double)i.Element("Lat"),
CurrentImage = ResourceHelper.LoadBitmapURIFromResource((string)i.Element("Img"))
}).ToList();
CompListObs = new ObservableCollection<ComputerInfo>(items);
}
public void MainTimer_Tick(object sender, EventArgs e)
{
// This runs fine and I can see the members of CompListObs are changing,
// but the images on the mainwindow are not changing.
foreach(var comp in CompListObs) { comp.CurrentImage = ResourceHelper.LoadBitmapURIFromResource("another image");
}
// INotifyPropertyChanged
public event PropertyChangedEventHandler PropertyChanged = delegate { };
private void RaisePropertyChanged(string propName)
{
PropertyChanged(this, new PropertyChangedEventArgs(propName));
}
public class ComputerInfo : INotifyPropertyChanged
{
public ClientInfo ClientsInfo { get; set; }
public string MachineName { get; set; }
public Uri CurrentImage { set; get; }
public double Lat { get; set; }
public double Lon { get; set; }
public Uri currentImageNotifier
{
get { return CurrentImage; }
set
{
CurrentImage = value;
RaisePropertyChanged("compListObsNotifier");
}
}
// INotifyPropertyChanged
public event PropertyChangedEventHandler PropertyChanged = delegate { };
public void RaisePropertyChanged(string propName)
{
PropertyChanged(this, new PropertyChangedEventArgs(propName));
}
}
Here is the xaml:
<ListBox ItemsSource="{Binding compListObsNotifier}">
<ListBox.ItemTemplate>
<DataTemplate>
<Image Source="{Binding Path=CurrentImage}" Height="65"></Image>
</DataTemplate>
</ListBox.ItemTemplate>
<!-- after this, I place <ListBox.ItemsPanel> <ItemsPanelTemplate> and <Canvas> in the ListBox.

When you bind to an observable collection you are subscribing to changes in the collection (for instance, adding or removing items from the collection). This does not subscribe you to changes to properties on the individual items in the collection. As others have stated, if you want to bind to a property on the items, you will need to raise a PropertyChanged event when the property changes.
private Uri currentImage;
public Uri CurrentImage
{
get { return currentImage; }
set
{
currentImage = value;
RaisePropertyChanged("CurrentImage");
}
}
Note: You may want to wrap the setter in an if statement and use Uri.Compare() to determine if the given value is actually different from the current value. This way, you only raise a PropertyChanged event when the property actually changes.
Also, in your code example you are setting the CurrentImage property in this foreach loop:
foreach(var comp in CompListObs)
{
comp.CurrentImage = ResourceHelper.LoadBitmapURIFromResource("another image");
}
However, you're raising your PropertyChanged event from the currentImageNotifier property. It's okay to raise PropertyChanged events from a location outside of the property being modified, but you either need to replace the CurrentImage assignment in your foreach loop with currentImageNotifier, or modify your CurrentImage property to raise its own PropertyChanged event. As it stands, you're not actually raising a PropertyChanged event on the property you're binding to.
Honestly, it doesn't look like you even need the currentImageNotifier property. It's not doing anything you couldn't just do with the CurrentImage property directly.

When you are binding to CurrentImage and the value of CurrentImage changes, you must raise the property changed event for CurrentImage.
Based on the supplied code, you also could do this:
public Uri currentImageNotifier
{
get { return CurrentImage; }
set
{
CurrentImage = value;
RaisePropertyChanged("CurrentImage");
}
}

How to bind a combo-box to a collection of multi-language values in WPF?

I am trying to set up a multi-language application, so when the user changes the display language all the texts in all the open windows change automatically.
I am having issues through with binding combo-box control. The binding needs to be done in code-behind as I have dynamic content coming from a database, and sometimes I even have to create additional combo-boxes at runtime.
Also I do not want to keep the translations in the database because I do not want to query the database every time a user is changing the display language.
What I did until now:
in xaml:
<ComboBox x:Name="cmb"/>
and in C#:
public class MyCmbItem
{
public int Index { get; set; }
public string Text { get; set; }
}
private ObservableCollection<MyCmbItem> LoadText()
{
ObservableCollection<MyCmbItem> _result = new ObservableCollection<MyCmbItem>();
foreach (var _item in _list)
{
//the list is coming from a database read
_result.Add(new MyCmbItem { Index = _item.Value, Text = _res_man_global.GetString(_item.KeyText, _culture) });
}
return _result;
}
public ObservableCollection<MyCmbItem> MyTexts
{
get { return LoadText(); }
set {} //I do not have to add/remove items at runtime so for now I leave this empty
}
private void Window_Loaded(object sender, RoutedEventArgs e)
{
...
LoadList(); //this adds values in _list
cmb.ItemsSource = MyTexts; //this populates the combo-box
Here I got stuck and I do not know how to determine the combo-box to refresh the displayed texts. The method must achieve that if I have several windows opened each containing a random number of combo-boxes, when I change the current language all the combo-boxes in all the windows will refresh the displayed list, without affecting other values inside (like the selected item). Does anybody know how this can be done?
Many thanks.

For your xaml UI, the INotifyPropertyChanged interface indicates updates of the viewmodel. You can extend your class like this:
public class MyCmbItem : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void NotifyPropertyChanged(string APropertyName)
{
var property_changed = PropertyChanged;
if (property_changed != null)
{
property_changed(this, new PropertyChangedEventArgs(APropertyName));
}
}
private string _Text;
private string _KeyText;
public int Index { get; set; }
public string Text
{
get { return _Text;}
set {
if (_Text != value)
{
_Text = value;
NotifyPropertyChanged("Text");
}
}
}
public MyCmbItem(string key_text, int index)
{
Index = index;
_KeyText = key_text;
RefreshText();
_res_man_global.LanguageChanged += () => RefreshText();
}
public void RefreshText()
{
Text = _res_man_global.GetString(_KeyText, _culture);
}
}
Your view can simply bind to the Text-property as following:
<DataTemplate DataType="{x:Type local:MyCmbItem}">
<TextBlock Text="{Binding Path=Text}"/>
</DataTemplate>
Note: I assumed that your language class is global and has some kind of language-changed notification event.