I am binding a Datagrid to Observablecollection.Below is my ObservableCollection class.
But the Property changed is always NULL and it is null even after Making my XAML like this.
Please Guide me in this
Thanks!
<DataGridTextColumn Binding="{Binding, Mode=TwoWay, NotifyOnSourceUpdated=True, NotifyOnTargetUpdated=True, UpdateSourceTrigger=PropertyChanged} Header = "Serial" />
public class itemobject
{
public event PropertyChangedEventHandler PropertyChanged;
// This method is called by the Set accessor of each property.
// The CallerMemberName attribute that is applied to the optional propertyName
// parameter causes the property name of the caller to be substituted as an argument.
private void NotifyPropertyChanged( String propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
int sno1;
public int Sno
{
get
{ return sno1; }
set
{
if (value != sno1)
{
sno1= value;
NotifyPropertyChanged("Sno");
}
}
}
In XAML you should specify which property exactly changed.
<DataGridTextColumn Binding="{Binding Path = Sno} Header = "Serial" />
And like i did, you need to create ViewModelBase class.
public abstract class ViewModelBase : INotifyPropertyChanged, IDisposable {
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged([CallerMemberName]string propertyName = null) {
var handle = PropertyChanged;
handle?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
public virtual void Dispose() => PropertyChanged = null;
}
public class itemobject : ViewModelBase{
int sno1;
public int Sno{
get => sno1;
set{
if (value != sno1){
sno1= value;
OnPropertyChanged(nameof(Sno));
}
}
}
Related
I have been trying to detect it when these variables change, but I don't know how to do that since bools aren't supported by the "PropertyChanged" function.
I also tried using the communityToolKit, but I have no idea how to use that.
I want it to call the function "IconUpdater"
public class Status : INotifyPropertyChanged
{
public static bool isWorking { get; set; } = Preferences.Get("IsWorking", true);
public static bool isPaused { get; set; } = Preferences.Get("IsPaused", false);
public static void IconUpdater()
{
// The function I want to call \\
}
public event PropertyChangedEventHandler PropertyChanged;
}
You can use PropertyChanged event to notify the changes of IsEnabled property in your viewmodel.
Here's the code snippet below for your reference:
public class MainPageViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private bool _isWorking;
public bool IsEnabled
{
get
{
return _isWorking;
}
set
{
if(_isWorking != value)
{
_isWorking = value;
var args = new PropertyChangedEventArgs(nameof(IsEnabled));
PropertyChanged?.Invoke(this, args);
}
}
}
}
I recommend using the Community Toolkit MVVM package: https://learn.microsoft.com/en-us/dotnet/communitytoolkit/mvvm/
You can then simply do the following to use the INotifyPropertyChanged interface:
using CommunityToolkit.Mvvm;
public class MyViewModel : ObservableObject
{
private bool _myBool;
public bool MyBool
{
get => _myBool;
set => SetProperty(ref _myBool, value);
}
}
You can also modify the code in such a way that you directly call any other method from within the setter:
private bool _myBool;
public bool MyBool
{
get => _myBool;
set
{
SetProperty(ref _myBool, value);
IconUpdater();
}
}
Please mind that your class is using static properties. You cannot use INotifyPropertyChanged for that.
I have a background-thread which updates a Integer-value once per second. How can I map this Integer to a Text-Field of my XAML form that the Form always shows the current value and updates automatically if the Integer changes?
You can use a ViewModel with a binding.
With OnPropertyChanged() it will automatically changed and displayed in your UI.
here is an example to give you an idea
use in your xaml:
<TextBox x:Name="MyTextBox" Text="{Binding Name}".../>
in your code behind:
...
var vm = new ViewModel("Nr.7");
this.BindingContext = vm;
foreach(var x in Whatever)
{
vm.Name = x;
}
using System.ComponentModel;
using System.Runtime.CompilerServices;
namespace MyAppNamespace
{
// This class implements INotifyPropertyChanged
// to support one-way and two-way bindings
// (such that the UI element updates when the source
// has been changed dynamically)
public class ViewModel : INotifyPropertyChanged
{
private string name;
// Declare the event
public event PropertyChangedEventHandler PropertyChanged;
public ViewModel()
{
}
public ViewModel(string value)
{
this.name = value;
}
public string Name
{
get { return name; }
set
{
name = value;
// Call OnPropertyChanged whenever the property is updated
OnPropertyChanged();
}
}
// Create the OnPropertyChanged method to raise the event
// The calling member's name will be used as the parameter.
protected void OnPropertyChanged([CallerMemberName] string name = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
}
}
}
I have a ViewModel and a Class. They look like this:
//viewmodel
public class MyViewModel : ViewModelBase {
private MyClass myClass;
public MyClass MyClass{
get{
return myClass;
}
set{
this.myClass = value;
base.OnPropertyChanged();
}
}
private string testString;
public string TestString{
get{
return testString;
}
set{
this.testString = value;
base.OnPropertyChanged();
}
}
public MyViewModel(){
this.MyClass = new MyClass();
this.TestString = "blah, blah, blah"
}}
//class
public class MyClass : ViewModelBase{
private string myString;
public string MyString{
get {
return myString
}
set{
this.myString = value;
base.OnPropertyChanged();
}
}
public MyClass (){
this.MyString = "25"; }}
The base class - ViewModelBase implements INotifyChange and contains OnPropertyChanged handler logic.
I have a UserControl where I wish to bind values from MyClass like this:
<TextBlock Text="{x:Bind Path=MyViewModel.MyClass.MyString, Mode=TwoWay}"></TextBlock>
However this does not work. Value is binded in initialisation correctly, but any change in MyViewModel.MyClass.MyString is not reflected in texblock, the text remains the same. The OnPropertyChange is raised, the breakpoint in ViewModelBase is hit with MyString value changed, but it is somehow not propagated to texblock.
Binding on simple value from MyClass works like charm, this textblock is updated, when property is changed:
<TextBlock Text="{x:Bind Path=MyViewModel.TestString, Mode=TwoWay}"></TextBlock>
What am I missing? Why the textblock with binding to "MyViewModel.MyClass.MyString" is not being updated?
I have tested the code you provided and don't think there is any problem with it. Where the problem could be, however, is your Page's code-behind. By any chance, aren't you using this as the property declaration?
public MyViewModel MyViewModel => new MyViewModel();
Because in this case, every access to MyViewModel property evaluates as a new instance of MyViewModel class. In this configuration, you would properly change the property, but the UI would never notice, as you would update the property on a new instance. If you instead use
public MyViewModel MyViewModel { get; } = new MyViewModel();
You will get the correct behavior of creating only one instance when the page is created.
I have the following code:
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
}
public MyViewModel MyViewModel { get; } = new MyViewModel();
private void Button_Click(object sender, RoutedEventArgs e)
{
MyViewModel.MyClass.MyString = "test";
}
}
And my simple ViewModelBase:
public class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
I am very new to the MVVM style. I have been able to accomplish everything in the past by writing extensive code in the code behind the XAML. However, I am trying to convert everything into MVVM.
Issue:
I am unable to bind a datagrid to my ObservableCollection. When I debug and walk through my code, the ObservableCollection list is being properly set, meaning, i can view the data within the variables and it shows the data i am adding; however, my data grid does not display the data. Upon reading I found that if I used an ObservableCollection, I didn't need an INotifyPropertyChanged; but because that didn't work, i do have one on there now. Sadly, that still isn't populating my datagrid.
Any help you can offer is appreciated.
In the end, I am going to have a list of type Members, and i need the data grid to populate the data about each member. The data comes from the Members class.
Xaml:
<DataGrid ItemsSource="{Binding Source=PHList}" AutoGenerateColumns="False">
<DataGrid.Columns>
<DataGridTextColumn Header="Member Name" Binding="{Binding Member_Name}"/>
<DataGridTextColumn Header="Medicaid ID" Binding="{Binding Medicaid_ID}"/>
</DataGrid.Columns>
</DataGrid>
Priority Health Model:
public PriorityHealthMember(string name, string id)
{
Member_Name = name;
Medicaid_ID = id;
}
private string _Member_Name;
public String Member_Name
{
get
{
return _Member_Name;
}
set
{
_Member_Name = value;
OnPropertyChanged("Member_Name");
}
}
private string _Medicaid_ID;
public String Medicaid_ID
{
get
{
return _Medicaid_ID;
}
set
{
_Medicaid_ID = value;
OnPropertyChanged("Medicaid_ID");
}
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
Onboarding ViewModel
private ObservableCollection<PriorityHealthMember> _PHList;
public ObservableCollection<PriorityHealthMember> PhList
{
get
{
return _PHList;
}
set
{
_PHList = value;
OnPropertyChanged("PhList");
}
}
public OnboardingQueueViewModel()
{
PhList = GetOnboardingQueueList();
}
private ObservableCollection<PriorityHealthMember> GetOnboardingQueueList()
{
ObservableCollection<PriorityHealthMember> list = new ObservableCollection<PriorityHealthMember>();
list.Add(new PriorityHealthMember("Andrews, Nicholas", "M123456"));//Testing for now. Will add the Business Logic after binding works.
return list;
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
I found my issue. In my xaml i had "PHList" however, my property was "PhList"
In my project I am setting a bool property as true when constructing my ViewModel.
In the View, I have a RadioButton which is bound to the value of this property. The first time I open the View, the RadioButton is "checked" (perfect, exactly what I want!).
However, if I close and then re-open the View, the RadioButton is not "checked", despite the bound property having a value of 'true'. In my constructor I am setting 'StaggeredMode' to true, but the setter is being called three times (firstly, value = true; secondly, value = false; thirdly, value = true)
Any help will be appreciated!
XAML:
<RadioButton GroupName="AppointmentStart"
Content="Staggered"
IsChecked="{Binding StaggeredMode, Mode=TwoWay}"
VerticalAlignment="Top"
HorizontalAlignment="Left"
Margin="310,247,0,0" />
C#:
private bool staggeredMode;
public bool StaggeredMode
{
get { return staggeredMode; }
set { staggeredMode = value; }
}
Your StaggeredMode property should be observable so the view can be notified about property changes from your ViewModel.
You can implement INotifyPropertyChanged by yourself or use one of existing implementations like this, this or this.
Here is a basic implementation of INotifyPropertyChanged interface:
public abstract class ObservableObject : INotifyPropertyChanged
{
public virtual void RaisePropertyChanged(string propertyName)
{
OnPropertyChanged(propertyName);
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = this.PropertyChanged;
if (handler != null)
{
var e = new PropertyChangedEventArgs(propertyName);
handler(this, e);
}
}
}
Then you derive your ViewModel from ObservableObject and raise OnPropertyChanged event every time your property value has been changed:
public class MyViewModel : ObservableObject
{
...
private bool staggeredMode;
public bool StaggeredMode
{
get { return staggeredMode; }
set
{
staggeredMode = value;
OnPropertyChanged("StaggeredMode");
}
}
...
}