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c# WPF MVVM Set View Property From ViewModel

I want to create a simple Control to enter Text.
For this Control i want to create a Property.
This Property should be bind to the ViewModel.
I Created a Model for an Folder:
public class FolderModel : ModelBase
{
private string fullPath;
public string FullPath
{
get { return fullPath; }
set
{
if (fullPath == value)
return;
fullPath = value;
RaisePropertyChanged(nameof(FullPath));
}
}
}
In my View xaml i bound the Data to my ViewModel:
<UserControl.DataContext>
<Browser:FolderBrowserViewModel/>
</UserControl.DataContext>
<Grid>
<TextBox x:Name="TextBox_Folder" IsReadOnly="True" Text="{Binding Folder.FullPath}"/>
</Grid>
To Create the Property created this code in the View:
public string FullPath
{
get { return (string)GetValue(FolderFullPathProperty); }
set { SetValue(FolderFullPathProperty, value); }
}
public static readonly DependencyProperty FolderFullPathProperty = DependencyProperty.Register("FullPath", typeof(string), typeof(FolderBrowser), new PropertyMetadata("", new PropertyChangedCallback(OnSetTextChanged)));
private static void OnSetTextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
FolderBrowser UserControl1Control = d as FolderBrowser;
UserControl1Control.OnSetTextChanged(e);
}
private void OnSetTextChanged(DependencyPropertyChangedEventArgs e)
{
TextBox_Folder.Text = e.NewValue.ToString();
}
My ViewModel looks like this:
private ICommand _browseFolderCommand;
public ICommand BrowseFolderCommand
{
get
{
return _browseFolderCommand is null ? (_browseFolderCommand = new RelayCommand(() => BrowseFolder(), true)) : _browseFolderCommand;
}
}
private FolderModel folder = new FolderModel();
public FolderModel Folder
{
get { return folder; }
set
{
if (folder == value)
return;
folder = value;
}
}
private void BrowseFolder()
{
System.Windows.Forms.FolderBrowserDialog fbd = new System.Windows.Forms.FolderBrowserDialog();
if (fbd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
{
SetField(ref folder, Folder, "FullPath");
}
}
and my ViewModelBase looks like this:
public class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
=> PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
protected bool SetField<T>(ref T field, T value, [CallerMemberName] string propertyName = null)
{
if (EqualityComparer<T>.Default.Equals(field, value)) return false;
field = value;
OnPropertyChanged(propertyName);
return true;
}
protected void Dispatch(Action f) => Application.Current.Dispatcher.Invoke(f);
protected TResult Dispatch<TResult>(Func<TResult> f) => Application.Current.Dispatcher.Invoke(f);
}
if i use the Control i want to set the Property "FullPath"
when i set this Property the Value should be set to the ViewModels Folder.FullPath.
If this is set, the Binding of the TextBox and Folder.FullPath should show the correct path.
if its possible i want all Code in the ViewModel =)
Edit:
I tried to illustrate it a bit more pictorially:
On the left side you can see the control as it is placed on a window. There you can set MyProp to any value and the TextBox will receive it.
On the right side I have tried to show it in more detail.
The view has the label, a TextBox and a button.
The view also has the property "MyProp".
The textbox of the view is bound to the ViewModel, namely to the field "MyCoolFieldValue".
This means that if I do anything in the ViewModel with the field MyCoolFieldValue, I know that it will always have the value that is in the textbox.
If I now press the button, a command is called. This command changes the WErt of MyCoolFieldValue. When this happens, the value should be written directly back into the property and the textbox of the view.
However, I can't get this to work and have tried it with the code above.

I can't update my binding data(only update at first time)

I want to show the stream data to textbox in real time. But the textbox doesn't updated even the stream data has updated. I don't know what is wrong.
Here is my XAML code.
<TextBox Text="{Binding Path = marketPrice}" HorizontalAlignment="Left"/>
And this is View Model code.
public class OrderTestViewModel : INotifyPropertyChanged
{
public QuotesDataSource DataSource;
public string _marketPrice => DataSource.SymbolPrice;
public string marketPrice
{
get { return _marketPrice; }
set
{
RaisePropertyChanged("marketPrice");
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void RaisePropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
I checked the marketPrice is updated real time.
And the last is hidden code.
public partial class OrderTest : UserControl
{
OrderTestViewModel model = new OrderTestViewModel();
public OrderTest()
{
InitializeComponent();
DataContext = model;
}
}
Please help me.

It seems your marketPrice setter never update the value of _marketPrice (which will always show the same value.
Would you want something like :
public string _marketPrice = DataSource.SymbolPrice;
public string marketPrice
{
get { return _marketPrice; }
set
{
if (_marketPrice != value)
{
_marketPrice = value;
RaisePropertyChanged("marketPrice");
}
}
}

I want to update new value in UI when DataSource.SymbolPrice is updated. DataSource.SymbolPrice is updated periodly
Then you should bind directly to the SymbolPrice property and implement INotifyPropertyChanged and raise the PropertyChanged event in the QuotesDataSource class:
public class OrderTestViewModel
{
public QuotesDataSource DataSource;
public string marketPrice => DataSource.SymbolPrice;
}
Obviously some object must tell the UI when there is a update and this is the responsibility of the source object.
The view model cannot be supposed to know when the price is changed in the QuotesDataSource unless the latter tells it somehow, for example by raising an event.

WPF Prism DataGrid not updated

I've a problem with DataGrid in Prism MVVM.
When I edited entity in other window, then I create new window with DataGrid is not updated. Only run application again help. It's my code:
<DataGrid Name="ClientsTable" IsReadOnly="True" ItemsSource="{Binding Path=ListOfClients, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" AutoGeneratingColumn="DataGrid_AutoGeneratingColumn" Margin="22,10,22,55" Width="800"/>
Part of ViewModel for this window:
public ListOfClientsViewModel(IClientService clientService, IEventAggregator eventAggregator)
{
this.clientService = clientService;
this.eventAggregator = eventAggregator;
ListOfClients.AddRange(clientService.GetAllClientsForList());
}
private ObservableCollection<ClientForList> listOfClients = new ObservableCollection<ClientForList>();
public ObservableCollection<ClientForList> ListOfClients
{
get { return listOfClients; }
set { SetProperty(ref listOfClients, value); }
}
And part of model from collection. It's in other project.
public class ClientForList : INotifyPropertyChanged
{
private string id;
private string name;
private string firstname;
private string lastname;
private string city;
private DateTime createdDate;
[DisplayName("Numer klienta")]
public string Id
{
get { return id; }
set
{
if (value != id)
{
id = value;
OnPropertyChanged();
}
}
}
[DisplayName("Nazwa")]
public string Name
{
get { return name; }
set
{
if (value != name)
{
name = value;
OnPropertyChanged();
}
}
}
[DisplayName("Imię")]
public string Firstname
{
get { return firstname; }
set
{
if (value != firstname)
{
firstname = value;
OnPropertyChanged();
}
}
}
[.....]
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
And, when I edit entity in other window, then I open window with DataGrid by:
void ExecuteListOfClients()
{
ListOfClients listOfClientsWindow = new ListOfClients();
listOfClientsWindow.DataContext = new ListOfClientsViewModel(IClientService, EventAggregator);
listOfClientsWindow.ShowDialog();
}
And data in DataGrid is old. When I restart application data is actual. Help!

Instead of
set { SetProperty(ref listOfClients, value); }
do
set { SetProperty(listOfClients, value); }
and instead of
ListOfClients.AddRange(clientService.GetAllClientsForList());
do
ListOfClients = clientService.GetAllClientsForList().ToObservableCollection();
You may need to implement the extension ToObservableCollection().
Another solution is to change the property ListOfClients as a normal IList and then implment INotifyPropertyChanged inside your view model

Ok, I solved part of the problem.
I have cut the window creation without the manual creation of the ViewModel on:
void ExecuteListOfClients()
{
ListOfClients listOfClientsWindow = new ListOfClients();
listOfClientsWindow.ShowDialog();
}
And in xaml ListOfClients.xaml I changed to:
prism:ViewModelLocator.AutoWireViewModel="True"
And now, after reopening the window, it shows refreshed data;)
But there is still a problem. I've done the LoadData method, which is done in the constructor and assigns data to the ObservableCollection. It works. I have set a button for it and after editing the client I click to load new data and unfortunately nothing happens. In the future I want this method to be called from the EventAggregator after editing the client, but for now I have made a button to test and unfortunately it does not work.

It works. The problem was not in the WPF itself, nor was the view strangely enough. The problem lay in EntityFramework. I had to modify the command choosing data from the database to the collection:
var clients = db.Clients.AsNoTracking().ToList();

Can Indexers of a property work in xaml binding in windows phone 8?

something i do wrong? anyone gives some suggestions
according to msdn
Indexers of a property can be specified within square brackets following the property name where the indexer is applied. For instance, the clause Path=ShoppingCart[0] sets the binding to the index that corresponds to how your property's internal indexing handles the literal string "0". Multiple indexers are also supported.
i put Indexers of a property in my xaml
<Image Source="{Binding ImagePathList[0]}" Height="50" Width="50" Grid.Row="0" Grid.Column="0" VerticalAlignment="Top" Margin="0,7,7,0" Grid.RowSpan="2">
i do not give the viewmodel code because i am pretty sure ListImagePathList have data.
EDIT*
more detail: ImagePathList[0] is a web image url
EDIT FOR Brendan
model is Article
public class Article : INotifyPropertyChanged
{
private long _Id;
public long ID
{
get { return _Id; }
set
{
if (_Id != value)
{
_Id = value;
NotifyPropertyChanged();
}
}
}
private string _subject;
public string Subject
{
get
{
return _subject;
}
set
{
if (_subject != value)
{
_subject = value;
NotifyPropertyChanged();
}
}
}
private string _words;
public string Words
{
get
{
return _words;
}
set
{
if (_words != value)
{
_words = value;
NotifyPropertyChanged();
}
}
}
private DateTime _publishDate;
public DateTime PublishDate
{
get
{ return _publishDate; }
set
{
if (_publishDate != value)
{
_publishDate = value;
NotifyPropertyChanged();
}
}
}
public List<string> ImagePathList = new List<string>();
private string _firstImage;
public string FirstImage
{
get
{
return _firstImage;
}
set
{
if (_firstImage != value)
{
_firstImage = value;
NotifyPropertyChanged();
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged([CallerMemberName] string propertyName = "")
{
PropertyChangedEventHandler handler = PropertyChanged;
if (null != handler)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
ArticleViewModel is in below; All data returned from network is correct!
public class ArticleListViewModel : INotifyPropertyChanged
{
public ArticleListViewModel()
{
this.ArticleCollection = new ObservableCollection<Article>();
}
public ObservableCollection<Article> ArticleCollection
{
get;
private set;
}
public void LoadPage(int pageNumber)
{
if (pageNumber == 1)
{
this.ArticleCollection.Clear();
}
IsLoading = true;
ReadArticleList(pageNumber);
}
private async void ReadArticleList(int pageNumber)
{
try
{
List<Article> articleList = new List<Article>();
articleList = await CollectionHttpClient.GetArticlesByPageAsync(pageNumber);
this.ArticleCollection.Add(item);
}
}
catch(Exception ex)
{
if (ex.HResult == -2146233088 && ex.Message.Equals("Response status code does not indicate success: 404 ()."))
{
MessageBox.Show("The network is not set right. Internet cannot be accessed.");
}
else
{
MessageBox.Show("sorry, no data.");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (null != handler)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}

The XAML code you show is fine.
There may be a problem with the DataContext. Maybe the page DataContext has not been set? Or maybe the the DataContext has changed e.g. inside an ItemTemplate
Otherise the problem is probably to do with the bound property. Try the following
private ObservableCollection<string> _imagePathList = new ObservableCollection<string>();
public ObservableCollection<string> ImagePathList {
get { return this._imagePathList; }
set {
if (this._imagePathList != value)
{
this._imagePathList = value;
// I'm going to assume you have the NotifyPropertyChanged
// method defined on the view-model
this.NotifyPropertyChanged();
}
}
}
ObservableCollection is in System.Collections.ObjectModel and is like List but if elements are added/removed then the PropertyChanged event is fired. Also note that any bound property must have a get associated with it for it to work at all.
Another possibility is that ImagePathList was not assigned to or is empty - in which case, make sure you assign to it!
In case you have not yet implemented the NotifyPropertyChanged method, here it is ...
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
You will also need to add INotifyPropertyChanged interface to the containing class e.g.
public class MyViewModelClass : INoftifyPropertyChanged
{
...
}

I think the problem concerns the place where your images come from. As it is said at MSDN:
You can set the Source by specifying an absolute URL (e.g. http://contoso.com/myPicture.jpg) or specify a URL relative to the XAP file of your application.
You can set this property in XAML, but in this case you are setting the property as a URI. The XAML behavior relies on underlying type conversion that processes the string as a URI, and calls the BitmapImage(Uri) constructor. This in turn potentially requests a stream from that URI and returns the image source object.
Just for test - place some images in your project and then set ImagePathList to them. See if that works (it should as I think). Or see if you can get BitmapImage(ImagePathList);
It's hard for me to say now (as I don't know how your ImagePathList looks like) what could be a reason of the failure. But if I were you, I would test this.
I would advise to use a property (or you can use converter which will also do the job):
// a property in your class
public Uri FirstImage
{
get
{
return new Uri(ImagePathList.FirstOrDefault(), UriKind.Absolute);
}
}
On the other hand if you are downloading images to IsolatedStorage then you will have to use another property, that will load BitmapImage from IS:
public BitmapImage FirstImage // getter - BitmapImage
{
get
{
if (String.IsNullOrEmpty(ImagePath[0])) return null;
BitmapImage temp = new BitmapImage();
using (IsolatedStorageFile ISF = IsolatedStorageFile.GetUserStoreForApplication())
using (IsolatedStorageFileStream file = ISF.OpenFile(ImagePath[0], FileMode.Open, FileAccess.Read))
temp.SetSource(file);
return temp;
}
}
Hope this helps.

How to Pass a Value From a Window to a UserControl in WPF

I want to pass a value from MainWindow into my UserControl! I passed a value to my UserControl and the UserControl showed me the value in a MessageBox, but it is not showing the value in a TextBox. Here is my code:
MainWindow(Passing Value To UserControl)
try
{
GroupsItems abc = null;
if (abc == null)
{
abc = new GroupsItems();
abc.MyParent = this;
abc.passedv(e.ToString(), this);
}
}
catch (Exception ee)
{
MessageBox.Show(ee.Message);
}
UserControl
public partial class GroupsItems : UserControl
{
public MainWindow MyParent { get; set; }
string idd = "";
public GroupsItems()
{
InitializeComponent();
data();
}
public void passedv(string id, MainWindow mp)
{
idd = id.ToString();
MessageBox.Show(idd);
data();
}
public void data()
{
if (idd!="")
{
MessageBox.Show(idd);
texbox.Text = idd;
}
}
}
EDIT(using BINDING and INotifyProperty )
.....
public GroupsItems()
{
InitializeComponent();
}
public void passedv()
{
textbox1.Text = Text;
}
}
public class Groupitm : INotifyPropertyChanged
{
private string _text = "";
public string Text
{
get { return _text; }
set
{
if (value != _text)
{
_text = value;
NotifyPropertyChanged();
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void NotifyPropertyChanged(String propertyName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}

Problem here is with reference.
When you create new object in code behind, new object will be created and this is not the same object which you have in xaml code. So you should use following code:
<local:GroupsItems x:Name="myGroupsItems"/>
and in code behind you don't have to create new object. You should use object that you added in XAML:
...
myGroupsItems.MyParent = this;
myGroupsItems.passedv(e.ToString(), this);
...
Here is example solution (sampleproject).

You are calling data in the constructor when idd is still "" which results in the text box still being empty. Changing the MyParent property does not change that. Only passedv does. But at that point you do not have the parent set. Just call data in passedv, too.

Try this:
public partial class GroupsItems : UserControl
{
//properties and methods
private string idd="";
public string IDD
{
get{return idd;}
set{
idd=value;
textBox1.Text=idd;
}
}
//other properties and methods
}
Usage:
In your Main form:
abc = new GroupsItems();
abc.IDD="sometext";
MainGrid1.Children.Add(abc); //Grid or any other container for your UserControl

In your Binding example, your GroupItem class looks ok, except that you need to pass in the name of the changed property:
public string Text
{
get { return _text; }
set
{
if (value != _text)
{
_text = value;
NotifyPropertyChanged("Text");
}
}
}
Now, in GroupsItems, you shouldn't be accessing the TextBox. In WPF, we manipulate the data, not the UI... but as we use Binding objects to data bind the data to the UI controls, they automatically update (if we correctly implement the INotifyPropertyChanged interface).
So first, let's add a data property into your code behind (which should also implement the INotifyPropertyChanged interface) like you did in your GroupItem class:
private GroupItem _item = new GroupItem();
public GroupItem Item
{
get { return _item; }
set
{
if (value != _item)
{
_item = value;
NotifyPropertyChanged("Item");
}
}
}
Now let's try using a Binding on a TextBox.Text property:
<TextBox Text="{Binding Item.Text}" />
See how we bind the Text property of your GroupItem class to the TextBox.Text property... now all we need to do is to change the value of the Item.Text property and watch it update in the UI:
<Button Content="Click me" Click="Button_Click" />
...
private void Button_Click(object sender, RoutedEventArgs e)
{
Item.Text = "Can you see me now?";
}
Alternatively, you could put this code into your passedv method if you are calling that elsewhere in your project. Let me know how you get on.
UPDATE >>>
In your GroupItem class, try changing the initialization to this:
private string _text = "Any text value";
Can you now see that text in the UI when you run the application? If not, then try adding/copying the whole Text property into your code behind and changing the TextBox declaration to this:
<TextBox Text="{Binding Text}" />
If you can't see the text value now, you've really got problems... you have implemented the INotifyPropertyChanged interface in your code behind haven't you?