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WPF ObservableCollection binding to DataGrid not refreshing UI

I currently facing the issue that my DataGrid binding is not refreshing the UI.
My ViewModel and Object inherit from INotifyPropertyChanged.
Here is my code:
XAML:
<DataGrid Grid.Row="2" DataContext="{StaticResource MainViewModel}" ItemsSource="{Binding TestCollection, Mode=OneWay}" AutoGenerateColumns="True"/>
ViewModel:
public class MainViewModel: ViewModelBase
{
private ObservableCollection<ProductDisplayItem> _testCollection;
public ObservableCollection<ProductDisplayItem> TestCollection
{
get => _testCollection;
set => SetProperty(ref _testCollection, value);
}
private async void SendSearch()
{
//MyCode
.....
IEnumerable<ProductDisplayItem> displayItems = DisplayItemHelper.ConvertToDisplayItems(products);
TestCollection = new ObservableCollection<ProductDisplayItem>(displayItems);
}
}
My Object:
public class ProductDisplayItem: ViewModelBase
{
private string _mfrPartNumber;
private double _unitPrice;
private int _stock;
public string MfrPartNumber
{
get => _mfrPartNumber;
set => SetProperty(ref _mfrPartNumber, value);
}
public double UnitPrice
{
get => _unitPrice;
set => SetProperty(ref _unitPrice, value);
}
public int Stock
{
get => _stock;
set => SetProperty(ref _stock , value);
}
public ProductDisplayItem()
{
}
public ProductDisplayItem(string mfrp, double unitPrice, int stock)
{
MfrPartNumber = mfrp;
UnitPrice = unitPrice;
Stock = stock;
}
}
And my ViewModelBase:
public abstract class ViewModelBase: IDisposable, INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
protected virtual bool SetProperty<T>(ref T storage, T value, [CallerMemberName] string propertyName = "")
{
if (EqualityComparer<T>.Default.Equals(storage, value))
return false;
storage = value;
OnPropertyChanged(propertyName);
return true;
}
public void Dispose()
{
}
}
I also tried to add the items to the ObservableCollection instead of creating a new one, but with the same result.
I hope anyone can help me with that.
Thanks in advance

The most common cause of such errors is confusion about ViewModel instances: UI elements are bound to one instance, and you are modifying a collection in another instance.
Since WPF MVVM usually provides for using the main ViewModel in only one instance, try using Singleton.
Fresh topic with a similar question: Is it a correct approach to create static viewModel in MVVM?
First implementation option from there:
1) If:
in general, in principle, under no circumstances is it assumed that a ViewModel can have several instances at the assembly level in which it is created;
if this does not create any security problems, since the static instance can be accessed by everyone;
if static values are sufficient to create a single instance. In most cases, this means that the ViewModel has only one non-parameterized constructor.
Then in this case it is worth using Singleton.
Example:
public class MainWindowViewModel : ViewModelBase
{
// The only instance available outside of this class.
public static MainWindowViewModel Instanse { get; }
= new MainWindowViewModel();
// All constructors must be MANDATORY HIDDEN.
private MainWindowViewModel()
{
// Some code
}
// Some code
}
To get this instance in XAML, x: Static is used.
You can get the entire instance, or create a binding to a separate property.
<SomeElement
DataContext="{x:Static vm:MainWindowViewModel.Instance}"/>
<SomeElement
Command="{Binding ButtonCommandEvent,
Source={x:Static vm:MainWindowViewModel.Instance}}"/>

Ok I figured it out. It's the DataContext...
Works fine after removing it from xaml.

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.

Bind CheckListBox to ViewModel

I'm using a CheckListBox from the WPF Toolkit and trying to bind it to my ViewModel. In addition to obtaining the selected values from the control I would also like to be able to reset it through a button click which would clear any selections. I'm stuck on how to bind the selected or checked state of each item in the collection, but if my whole approach is off I would appreciate some direction on that as well.
I've created a simple class with a string descriptor and a Boolean property that I planned to use to indicate the state of each checkbox...
public class DrugInfluence : INotifyPropertyChanged
{
public string Impairment { get; set; }
private bool isChecked;
public bool IsChecked
{
get { return isChecked; }
set
{
if(isChecked != value)
{
isChecked = value;
OnPropertyChanged("IsChecked");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string info)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(info));
}
}
}
A collection of DrugInfluence objects in the ViewModel called ImpairmentList that I want to bind to the CheckListBox control iteself...
public List<DrugInfluence> ImpairmentList
{
get
{
return impairmentList;
}
set
{
if(impairmentList != value)
{
impairmentList = value;
NotifyPropertyChanged("ImpairmentList");
}
}
}
And the XAML I'm using to bind the ViewModel to the CheckListBox control...
<sdk:CheckListBox Margin="6"
ItemsSource="{Binding ImpairmentList}"
DisplayMemberPath="Impairment"
SelectedMemberPath="IsChecked"
SelectedItemsOverride="{Binding SelectedImpairments, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
</sdk:CheckListBox>

Is this the control you are using? If so, it looks like SelectedMemberPath is the property you want to bind to. You will also need to raise an event when the IsChecked property changes if you want to check/uncheck programatically. For instance,
public class DrugInfluence : INotifyPropertyChanged
{
public string Impairment { get; set; }
private bool _isChecked;
public bool IsChecked
{
get{ return _isChecked;}
set
{
if (_isChecked!= value)
{
_isChecked= value;
OnPropertyChanged("IsChecked");
}
};
}
}
And then implement the rest of the INotifyPropertyChanged members

UWP MVVM Data Binding for dummies (textbox.text from String)

Well, having a go at MVVM with UWP template 10. I have read many pages, and although everyone tries to say its really easy, I still can't make it work.
To put it into context, OCR is being run on an image, and I would like the text to be displayed in textbox automatically.
Here is my Model:
public class TextProcessing
{
private string _ocrText;
public string OcrText
{
get { return _ocrText; }
set
{
_ocrText = value;
}
}
}
Here is my ViewModel:
public class ScanPageViewModel : ViewModelBase, INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private TextProcessing _ocrTextVM;
public ScanPageViewModel()
{
_ocrTextVM = new TextProcessing();
}
public TextProcessing OcrTextVM
{
get { return _ocrTextVM; }
set {
_ocrTextVM = value;
this.OnPropertyChanged("OcrTextVM");
}
}
public void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
Here is my View:
<TextBox x:Name="rtbOcr"
Text="{Binding OcrTextVM.OcrText, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
Firstly, that is not working. Could someone try to show where I am going wrong?
Then, the data is coming from a Services file, how would the Services update the value? What would be the correct code?
Thanks in advance.

Following code is cite from code.msdn (How to achieve MVVM design patterns in UWP), it will be helpful for you:
Check you code step by step.
1.ViewModel implemented interface INotifyPropertyChanged,and in property set method invoked PropertyChanged, like this:
public sealed class MainPageViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string _productName;
public string ProductName
{
get { return _productName; }
set
{
_productName = value;
if (PropertyChanged != null)
{
PropertyChanged.Invoke(this, new PropertyChangedEventArgs(nameof(ProductName)));
}
}
}
}
2.Initialize you ViewMode in you page, and set DataContext as the ViewMode, like this:
public sealed partial class MainPage : Page
{
public MainPageViewModel ViewModel { get; set; } = new MainPageViewModel();
public MainPage()
{
...
this.DataContext = ViewModel;
}
}
3.In you xaml, binding data from viewMode, like this:
<TextBox Text="{Binding Path=ProductName,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Name="ProductNameTextBox" TextChanged="ProductNameTextBox_TextChanged" />

Your OnPropertyChanged call on OcrTextVM isn't actually called in your case, since you set the value in the constructor to its backing field and bypass the property.
If you set the value via the property, it should work:
public ScanPageViewModel()
{
OcrTextVM = new TextProcessing();
}
Of course your view needs to know that ScanPageViewModel is its DataContext. Easiest way to do it is in the constructor of the code-behind of your view:
public OcrView()
{
DataContext = new ScanPageViewModel();
InitializeComponent();
}
Assuming your OCR service is returning a new TextProcessing object on usage, setting the property of OcrTextVM should suffice:
public class ScanPageViewModel : ViewModelBase, INotifyPropertyChanged
{
//...
private void GetOcrFromService()
{
//...
TextProcessing value = OcrService.Get();
OcrTextVM = value;
}
}
On a note, the OcrTextVM name doesn't really reflect what the property is doing, since it doesn't look like it's a viewmodel. Consider renaming it.

Actually, it is very easy once I manage to understand. Here is the code needed to update a TextBox.Text
In the Models:
public class DisplayText : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string _text;
public string Text
{
get { return _text; }
set
{
_text = value;
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Text)));
}
}
}
In the XAML file:
<TextBox Text="{Binding Helper.Text, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" ... />
In the ViewModels:
private DisplayText _helper = new DisplayText();
public DisplayText Helper
{
get { return _helper; }
set
{
_helper = value;
}
}
Then any mod from the ViewModels:
Helper.Text = "Whatever text, or method returning a string";

WPF Databind control in write-only mode

I'm trying to fiddle a little with WPF bindings, so I created a simple project.
Here's the code:
public class Person : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public int Age {
get { return age; }
set {
age = value;
FirePropertyChanged("Age");
}
}
public string Name
{
get { return name; }
set
{
name = value;
FirePropertyChanged("Name");
}
}
private void FirePropertyChanged(string v)
{
if(PropertyChanged !=null)
PropertyChanged(this, new PropertyChangedEventArgs(v));
}
private int age;
private string name;
}
My viewmodel contains ObservableCollection of Person, and single Person to track selected Person.
I've bound listbox's ItemsSource to ObservableCollection, and SelectedItem to single Person, called CurrentPerson. Also, I've bound TextBox to CurrentPerson.Name.
Code works fine, but whenever I change content of TextBox - my listbox also changes. And no matter what combination of "OneWay, TwoWay, OneWayToSource" binding modes on listbox\selecteditem I cannot prevent listbox from updating from CurrentPerson.
How can I prevent this behavior? I'd like to update listbox from CurrentPerson only by using ICommand interface from VM.

There is only one copy of the Person object which is being used in both ListBox.ItemsSource and TextBox.Text, so naturally updating that object from one location will reflect the change in the other as well.
Two easy solutions would be
Change the BindingMode on TextBox.Text to Explicit, so it doesn't update the Person object until you tell it to
Use a separate string property for TextBox.Text and copy it over to your SelectedPerson.Name whenever the command executes
Personally I prefer the second option because I'm not a big fan of bindings that don't accurately reflect the data object behind the UI component, and it would allow the user to change the SelectedItem without resetting the TextBox value.
For an example of the second option, your ViewModel might look like this :
public class MyViewModel()
{
ObservableCollection<Person> People { get; set; }
Person SelectedPerson { get; set; }
string NewPersonName { get; set; }
ICommand UpdatePersonName { get; }
}
where the UpdatePersonName command would execute
SelectedPerson.Name = NewPersonName;
and the CanExecute would only return true if
SelectedPerson != null
&& !NewPersonName.IsNullOrWhiteSpace()
&& NewPersonName != SelectedPerson.Name

I'm not sure if I've followed the question properly.
So, we have a class Person as
public class Person : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public int Age
{
get { return age; }
set
{
age = value;
FirePropertyChanged("Age");
}
}
public string Name
{
get { return name; }
set
{
name = value;
FirePropertyChanged("Name");
}
}
private void FirePropertyChanged(string v)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(v));
}
private int age;
private string name;
}
And we have a view model as
public class ViewModel : INotifyPropertyChanged
{
public ObservableCollection<Person> List { get; set; }
Person currentPerson;
public Person CurrentPerson {
get { return currentPerson; }
set { currentPerson = value;
FirePropertyChanged("CurrentPerson");
}
}
private void FirePropertyChanged(string v)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(v));
}
public event PropertyChangedEventHandler PropertyChanged;
}
The xaml is
<ListBox ItemsSource="{Binding List}" SelectedItem="{Binding CurrentPerson}">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBox Text="{Binding Name}" Width="100" />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
And I bind the view model to the view via
ViewModel vm = new ViewModel();
vm.List = new ObservableCollection<Person>();
foreach (var i in Enumerable.Range(1,10))
{
vm.List.Add(new Person() { Name = "Test" + i.ToString(), Age= i });
}
vm.CurrentPerson = null;
this.DataContext = vm;
Whenever I change the value at textbox, it updates the name properly. I tried to add a handler for list changed, but it doesn't happen to get triggered.
vm.List.CollectionChanged += List_CollectionChanged;
void List_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
MessageBox.Show(e.Action.ToString());
}
Can you comment if it isn't the same as your problem statement?

If you want to control when and what is saved/updated, you obviously need is a ViewModel for editing your Person model.
When selecting a person in your Listbox, you have to pass the person's id (avoid passing the object itself) to the PersonEditViewModel which is bound to the properties that shall be edited, load the persons data into the PersonEditViewModel and then edit. Once you hit the "Save" button, it should commit the change and update the database or whatever you are using for persistence.
Use either events/messages to pass values/events back and forth, or use a navigation approach (like INavigationAware interface in Prism).