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Why doesnt my button update to enabled after the command finishes?

So I'm currently looking into commands and what I've done as of right now is that I made a command, bound it to a button and I've passed in a bool property which will indicate whether or not the button can execute the command.
The issue is that the button starts off as enabled, and as soon as I click it, it turns disabled, and then the person gets added to the ListView, but the button stays disabled.
I'm not sure if I need to add a UpdateSourceTrigger to the command, I thought the whole point of implementing a ObservableObject was to not have to do that.
What's the proper way of achieving what I'm trying to achieve?
The Command
public class RelayCommand : ICommand
{
private Action<object> execute;
private Func<object, bool> canExecute;
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
public RelayCommand(Action<object> execute, Func<object, bool> canExecute = null)
{
this.execute = execute;
this.canExecute = canExecute;
}
public bool CanExecute(object parameter)
{
return this.canExecute == null || this.canExecute(parameter);
}
public void Execute(object parameter)
{
this.execute(parameter);
}
}
The MainWindow (DataContext)
<Window x:Class="Commands.MainWindow"
...
Title="MainWindow"
Height="450"
Width="800">
<Window.DataContext>
<viewmodel:MainViewModel />
</Window.DataContext>
<StackPanel HorizontalAlignment="Center"
VerticalAlignment="Center">
<ListView MinHeight="100"
ItemsSource="{Binding PeopleCollection}">
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}"/>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<Button Content="Add"
Width="100"
Height="25"
Command="{Binding AddPersonCommand}" />
</StackPanel>
</Window>
The MainViewModel
internal class MainViewModel : ObservableObject
{
public ObservableCollection<PersonModel> PeopleCollection { get; set; }
/* A slow working command */
public RelayCommand AddPersonCommand { get; set; }
private bool _canExecute;
public bool CanExecute
{
get { return _canExecute; }
set
{
_canExecute = value;
NotifyPropertyChanged("CanExecute");
}
}
public MainViewModel()
{
CanExecute = true;
PeopleCollection = new ObservableCollection<PersonModel>();
AddPersonCommand = new RelayCommand(o => AddPersonToCollection(o), (p) => CanExecute);
}
private async void AddPersonToCollection(object o)
{
CanExecute = false;
await Task.Factory.StartNew(() =>
{
/* Simulate a heavy workload*/
Thread.Sleep(5000);
Application.Current.Dispatcher.BeginInvoke(() =>
{
PeopleCollection.Add(new PersonModel
{
Id = 0,
Name = "Foo bar"
});
});
/* Property needs to be updated from the main thread? */
//CanExecute = false;
});
CanExecute = false;
}
}
The ObservableObject
internal class ObservableObject : INotifyPropertyChanged
{
public event PropertyChangedEventHandler? PropertyChanged;
public void NotifyPropertyChanged([CallerMemberName] String propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}

I'm failing to see how your Button is actually being marked as disabled. I see the CanExecute bool being manipulated, but your button doesn't have IsEnabled bound. Even if that is the case, as #PaulSinnema said, you are only setting CanExecute to false (besides the first set in the constructor). I would suggest trying to set CanExecute = true inside of your Task and inside your lambda function (in the BeginInvoke) so then you can ensure the timing is correct. As you currently have it, your AddPersonToCollection method is doing the following:
Sets CanExecute to false
Fires off a task and waits for it to complete
Sets CanExecute to false
Here's my suggestion, hopefully it helps:
private async void AddPersonToCollection(object o)
{
CanExecute = false;
await Task.Factory.StartNew(() =>
{
/* Simulate a heavy workload*/
Thread.Sleep(5000);
Application.Current.Dispatcher.BeginInvoke(() =>
{
PeopleCollection.Add(new PersonModel
{
Id = 0,
Name = "Foo bar"
});
// Setting it here ensures we flip it as soon as the collection has a person added
CanExecute = true;
});
});
// Remove this line
///CanExecute = false;
}

Change WPF DataGrid column cell background color based on values

I am trying to fill cells with color in certain column. Column name is "NRO" and I want to fill cells staring with 2 yellow color and cells starting with 3 blue color. I went through answer given here: Change DataGrid cell colour based on values
Also tried several other approaches but can't get any of them work. I also don't understand how to implement any of them in my setup. They all seems to have <DataGridTextColumn Binding="{Binding Name}">. What it should be in my case?
Here is my XAML:
<Window x:Class="DB_inspector_FilterTest.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
Title="DB database inspector v.0.0.01" Height="600" Width="1000" Icon="logo_icon-small.jpg" Background="White">
<Grid Background="White">
<Grid.ColumnDefinitions>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<DataGrid x:Name="DataGrid1" Margin="0,103,0,0" Background="White" BorderBrush="#FF38853F"/>
<TextBox x:Name="NameSearch" HorizontalAlignment="Left" Height="20" Margin="22,41,0,0" TextWrapping="Wrap" Text="" VerticalAlignment="Top" Width="437" TextChanged="NameSearch_TextChanged"/>
<Button Content="Load" Margin="640,41,0,0" Click="Button_Click_1" BorderBrush="{x:Null}" Foreground="White" Background="#FF55B432" Width="66" Height="29" HorizontalAlignment="Left" VerticalAlignment="Top"/>
<ProgressBar x:Name="ProgressBar" HorizontalAlignment="Left" Height="11" VerticalAlignment="Top" Width="992" BorderBrush="{x:Null}" Background="{x:Null}"/>
<Label Content="Customer name" HorizontalAlignment="Left" Height="25" Margin="22,11,0,0" VerticalAlignment="Top" Width="154"/>
<CheckBox x:Name="ActiveCustomer" Content="Active" HorizontalAlignment="Left" Height="24" Margin="486,63,0,0" VerticalAlignment="Top" Width="86" Click="ActiveCustomer_Click_1"/>
<CheckBox x:Name="Only" Content="Leave only good" HorizontalAlignment="Left" Height="17" Margin="486,41,0,0" VerticalAlignment="Top" Width="115" Click="CheckBox_Click"/>
<Image Margin="856,0,22,520" VerticalAlignment="Bottom" Source="logo_small.jpg" Height="27"/>
</Grid>
</Window>
ADDITION:
If anybody have time, while I will be trying to figure it out myself, give me some hints how to proceed with my application, here is my full code:
using System.Data.Odbc;
using System.Windows;
using System.Data;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System;
namespace DB_inspector_FilterTest
{
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private async void Button_Click_1(object sender, RoutedEventArgs e)
{
try
{
ProgressBar.IsIndeterminate = true;
DataGrid1.ItemsSource = await GetDataAsync();
ProgressBar.IsIndeterminate = false;
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
private Task<DataView> GetDataAsync()
{
return Task.Run(() =>
{
string connectionStringDE = "Driver={Pervasive ODBC Client Interface};ServerName=DB123;dbq=#DBFSSE;Uid=ADMIN;Pwd=123;";
string queryStringDE = "select NRO,NAME,NAMEA,NAMEB,ADDRESS,POSTA,POSTN,POSTB,CORPORATION,COUNTRY,ID,ACTIVE from COMPANY";
string connectionStringFR = "Driver={Pervasive ODBC Client Interface};ServerName=DB123;dbq=#DBFSFI;Uid=ADMIN;Pwd=123;";
string queryStringFR = "select NRO,NAME,NAMEA,NAMEB,ADDRESS,POSTA,POSTN,POSTB,CORPORATION,COUNTRY,ID,ACTIVE from COMPANY";
DataTable dataTable = new DataTable("COMPANY");
// using-statement will cleanly close and dispose unmanaged resources i.e. IDisposable instances
using (OdbcConnection dbConnectionDE = new OdbcConnection(connectionStringDE))
{
dbConnectionDE.Open();
OdbcDataAdapter dadapterDE = new OdbcDataAdapter();
dadapterDE.SelectCommand = new OdbcCommand(queryStringDE, dbConnectionDE);
dadapterDE.Fill(dataTable);
}
using (OdbcConnection dbConnectionFR = new OdbcConnection(connectionStringFR))
{
dbConnectionFR.Open();
OdbcDataAdapter dadapterFR = new OdbcDataAdapter();
dadapterFR.SelectCommand = new OdbcCommand(queryStringFR, dbConnectionFR);
var newTable = new DataTable("COMPANY");
dadapterFR.Fill(newTable);
dataTable.Merge(newTable);
}
return dataTable.DefaultView;
});
}
private Dictionary<string, string> _conditions = new Dictionary<string, string>();
private void UpdateFilter()
{
try
{
var activeConditions = _conditions.Where(c => c.Value != null).Select(c => "(" + c.Value + ")");
DataView dv = DataGrid1.ItemsSource as DataView;
dv.RowFilter = string.Join(" AND ", activeConditions);
}
catch (Exception)
{
//MessageBox.Show(ex.Message);
}
}
private void NameSearch_TextChanged(object sender, System.Windows.Controls.TextChangedEventArgs e)
{
string filter = NameSearch.Text;
if (string.IsNullOrEmpty(filter))
_conditions["name"] = null;
else
_conditions["name"] = string.Format("NAME Like '%{0}%'", filter);
UpdateFilter();
}
private void ActiveCustomer_Click_1(object sender, RoutedEventArgs e)
{
if (ActiveCustomer.IsChecked == true)
{
_conditions["active"] = string.Format("ACTIVE Like '%{0}%'", "1");
UpdateFilter();
}
else
{
_conditions["active"] = null;
UpdateFilter();
}
}
private void CheckBox_Click(object sender, RoutedEventArgs e)
{
if (OnlyFIandSE.IsChecked == true)
{
_conditions["onlyfrandde"] = string.Format("NRO Like '2%' OR NRO Like '3%'");
UpdateFilter();
}
else
{
_conditions["onlyfrandde"] = null;
UpdateFilter();
}
}
}
}
Things I don't understand at least now: How in my case I should setup ItemSource for binding? Should I import databases to List first and then Bind to the list?
ATTEMPT 3:
Here is my latest MVVM attempt.
C#:
using System;
using System.ComponentModel;
using System.Data;
using System.Data.Odbc;
using System.Windows;
using System.Windows.Input;
namespace DB_inspector
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
}
public class ViewModel : INotifyPropertyChanged
{
public ICommand myCommand => new RelayCommand(obj =>
{
try
{
string connectionStringDE = "Driver={Pervasive ODBC Client Interface};ServerName=DB123;dbq=#DBFSSE;Uid=ADMIN;Pwd=123;";
string queryStringDE = "select NRO,NAME,NAMEA,NAMEB,ADDRESS,POSTA,POSTN,POSTB,CORPORATION,COUNTRY,ID,ACTIVE from COMPANY";
string connectionStringFR = "Driver={Pervasive ODBC Client Interface};ServerName=DB123;dbq=#DBFSFI;Uid=ADMIN;Pwd=123;";
string queryStringFR = "select NRO,NAME,NAMEA,NAMEB,ADDRESS,POSTA,POSTN,POSTB,CORPORATION,COUNTRY,ID,ACTIVE from COMPANY";
DataTable dataTable = new DataTable("COMPANY");
// using-statement will cleanly close and dispose unmanaged resources i.e. IDisposable instances
using (OdbcConnection dbConnectionDE = new OdbcConnection(connectionStringDE))
{
dbConnectionDE.Open();
OdbcDataAdapter dadapterDE = new OdbcDataAdapter();
dadapterDE.SelectCommand = new OdbcCommand(queryStringDE, dbConnectionDE);
dadapterDE.Fill(dataTable);
}
using (OdbcConnection dbConnectionFR = new OdbcConnection(connectionStringFR))
{
dbConnectionFR.Open();
OdbcDataAdapter dadapterFR = new OdbcDataAdapter();
dadapterFR.SelectCommand = new OdbcCommand(queryStringFR, dbConnectionFR);
var newTable = new DataTable("COMPANY");
dadapterFR.Fill(newTable);
dataTable.Merge(newTable);
}
_ = dataTable.DefaultView;
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
});
private bool _allowUIChanges = true;
public bool AllowUIChanges
{
get => _allowUIChanges;
set
{
_allowUIChanges = value;
OnPropertyChanged(nameof(AllowUIChanges));
OnPropertyChanged(nameof(IsReadOnlyDataGrid));
}
}
private void OnPropertyChanged(string v)
{
throw new NotImplementedException();
}
public bool IsReadOnlyDataGrid
{
get => !_allowUIChanges;
}
public event PropertyChangedEventHandler PropertyChanged;
}
public class RelayCommand : ICommand
{
private readonly Action<object> _execute;
private readonly Func<object, bool> _canExecute;
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
public RelayCommand(Action<object> execute, Func<object, bool> canExecute = null)
{
_execute = execute;
_canExecute = canExecute;
}
public bool CanExecute(object parameter) => _canExecute == null || _canExecute(parameter);
public void Execute(object parameter) => _execute(parameter);
}
}
XAML:
<Window x:Class="DB_inspector.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
Title="DB database inspector" Height="595.404" Width="1005.571">
<Grid>
<Grid.RowDefinitions>
<RowDefinition/>
</Grid.RowDefinitions>
<DataGrid IsReadOnly="{Binding IsReadOnlyDataGrid}" AutoGenerateColumns="False" ItemsSource="{Binding MyCollection}" Width="998" Margin="0,98,0,0" >
</DataGrid>
<Image Height="41" Margin="0,21,10,0" Width="141" Source="logo_small.jpg" HorizontalAlignment="Right" VerticalAlignment="Top"/>
<Button Content="Go" Command="{Binding myCommand}" Width="80" Height="30" Margin="48,42,870,492"/>
</Grid>
</Window>
Any suggestions what is still wrong here? No errors, but button does not process anything.

I suggest IValueConverter or IMultiValueConverter binding for Cell's Background property.
I'm not sure how it works with autogenerated columns set but with manual it looks like this. I'm providing here not a working copy but a markup example.
XAML
<Window.Resources>
<local:MyCellBackgroundConverter x:Key="myCellBackgroundConverter"/>
</Window.Resources>
<Window.DataContext>
<local:ViewModel/>
</Window.DataContext>
<Grid>
<!-- some your markup here -->
<DataGrid AutoGenerateColumns="False" ItemsSource="{Binding MyCollection}">
<DataGridTextColumn Header="Column1" Binding="{Binding Value1}">
<DataGridTextColumn.CellStyle>
<Style TargetType="DataGridCell">
<Setter Property="Background">
<Setter.Value>
<MultiBinding Converter="{StaticResource myCellBackgroundConverter}">
<Binding Path="Value1"/>
<Binding Path="Value2"/>
</MultiBinding>
</Setter.Value>
</Setter>
</Style>
</DataGridTextColumn.CellStyle>
</DataGridTextColumn>
<DataGridTextColumn Header="Column2" Binding="{Binding Value2}"/>
</DataGrid>
</Grid>
The ViewModel Class
using System.Collections.ObjectModel;
using System.ComponentModel;
// ...
public class ViewModel : INotifyPropertyChanged
{
private ObservableCollection<MyItem> _myCollection = new ObservableCollection<MyItem>();
public ObservableCollection<MyItem> MyCollection
{
get => _myCollection;
set
{
_myCollection = value;
OnPropertyChanged(nameof(MyCollection));
}
}
public ViewModel()
// you may load or add the data to MyCollection here
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
=> PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
Item
using System.ComponentModel;
// ...
public class MyItem : INotifyPropertyChanged
{
private string _value1 = string.Empty;
private string _value2 = string.Empty;
public string Value1
{
get => _value1;
set { _value1 = value; OnPropertyChanged(nameof(Value1)); }
}
public string Value2
{
get => _value2;
set { _value2 = value; OnPropertyChanged(nameof(Value2)); }
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
=> PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
And finally the Converter
using System;
using System.Globalization;
using System.Windows.Data;
using System.Windows.Media;
//...
public class MyCellBackgroundConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
if (values[0] is string value1 && values[1] is string value2)
{
if (value1.Length > 0)
{
return Brushes.Green;
}
else
if (value2.Length > 0)
{
return Brushes.Yellow;
}
else
return Brushes.Red;
}
else return Brushes.White;
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture) => null;
}
In alternative way you may use Style.DataTriggers directly in XAML.
For additional information about bindings and properties look for MVVM programming pattern. In short you're not need x:Name anymore because in MVVM pattern you interacting only with ViewModel class data instances and can't interact with contols directly there (and that's fine). Meanwhile Contols automatically sync with data binded to them. Calling OnPropertyChanged("PropertyName") here simply cause the GUI refresh.
In relation to markup of your XAML example, try wrapping the Control groups in StackPanel and learn about it. It will save your time spent fighting with margins. Simply set few colums and/or rows in Window's Grid and place StackPanels there assigning Grid.Column and Grid.Row to them.
ADDITION:
How in my case I should setup ItemSource for binding? Should I import databases to List first and then Bind to the list?
ObservableCollection<> is same as List<> and you may use it in the same way. The difference that first one implements CollectionChanged event that notifies DataGrid if any items was added or removed from the collection.
Your Button.Click event handler contains redundant async/await declaration.
Let's move forward and see how it can be done with MVVM.
XAML
<Button Content="Go" Command="{Binding myCommand}"/>
Command must implement ICommand interface. You have to do 2 things for proper implementation:
1) Add RelayCommand separate Class implementing ICommand interface
public class RelayCommand : ICommand
{
private readonly Action<object> _execute;
private readonly Func<object, bool> _canExecute;
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
public RelayCommand(Action<object> execute, Func<object, bool> canExecute = null)
{
_execute = execute;
_canExecute = canExecute;
}
public bool CanExecute(object parameter) => _canExecute == null || _canExecute(parameter);
public void Execute(object parameter) => _execute(parameter);
}
2) Add the Command instance to your ViewModel class
public ICommand myCommand => new RelayCommand(obj =>
{
// do the same here as in Button.Click above
});
Next, you may need some blocking UI thing that will prevent user from any actions while data is loading.
ViewModel
private bool _allowUIChanges = true;
public bool AllowUIChanges
{
get => _allowUIChanges;
set
{
_allowUIChanges = value;
OnPropertyChanged(nameof(AllowUIChanges));
OnPropertyChanged(nameof(IsReadOnlyDataGrid));
}
}
public bool IsReadOnlyDataGrid
{
get => !_allowUIChanges;
}
Finally bind your Control properties to it
XAML
<Button Content="Go" Command="{Binding myCommand}" Enabled="{Binding AllowUIChanges}"/>
<DataGrid IsReadOnly="{Binding IsReadOnlyDataGrid}" AutoGenerateColumns="False" ItemsSource="{Binding MyCollection}">
Then set AllowUIChanges to false while data is loading.

[UWP/MVVM]Enable/Disable Button in RadDataGrid Data Template Column that have commands bound to them upon conditions

I have set a bool property and have bound it to the IsEnabled in the xaml but the ICommand CanExecute method overrides the IsEnabled in xaml, so my bool property is ineffective.
When I define the conditions within the CanExecute method in the view model, It either disables all buttons in which the method is bound to, or enables all of them.
Its a grid that displays 3 different buttons for each row, and each button goes to a new xaml screen. If there is no data for the particular condition on the row the button is on then the button needs to be disabled.
How do i go about setting this so that buttons are disabled upon a condition?
Custom Command:
public class CustomCommand : ICommand
{
private Action<object> execute;
private Predicate<object> canExecute;
public CustomCommand(Action<object> execute, Predicate<object> canExecute)
{
this.execute = execute;
this.canExecute = canExecute;
}
public event EventHandler CanExecuteChanged
{
add
{
}
remove
{
}
}
public bool CanExecute(object parameter)
{
//throw new NotImplementedException();
bool b = canExecute == null ? true : canExecute(parameter);
return b;
}
public void Execute(object parameter)
{
execute(parameter);
}
}
xaml
<DataTemplate>
<Button Command="{Binding Source={StaticResource VM},
Path=Command}" CommandParameter="{Binding}" >
<SymbolIcon Symbol="Edit" Foreground="AliceBlue" />
</Button>
</DataTemplate>
CanExecute in VM
private bool CanGetDetails(object obj)
{
return true;
}

You can always do your conditional statement within the CanExecute function of your custom command, no need for you to bind IsEnabled property with your button that is bound to a command. Here's a sample implementation, hope this helps.
Custom Command:
public class CustomCommand<T> : ICommand
{
private readonly Action<T> _action;
private readonly Predicate<T> _canExecute;
public CustomCommand(Action<T> action, Predicate<T> canExecute)
{
_action = action;
_canExecute = canExecute;
}
public bool CanExecute(object parameter)
{
return _canExecute((T)parameter);
}
public void Execute(object parameter)
{
_action((T)parameter);
}
public event EventHandler CanExecuteChanged;
}
As you can see here, I created an object that implements the ICommand interface, this custom command accepts a generic type parameter which is used to evaluate a condition (CanExecute: this tells whether to enable or disable a command (in UI, the button), normally use to check for permissions, and other certain conditions) this parameter is also used to execute the action (Execute: the actual logic/action to be performed), The command contructor accepts delegate parameters that contain signatures for these 2 methods, the caller may choose lambda or standard methods to fillup these parameters.
Sample ViewModel:
public class ViewModel1: INotifyPropertyChanged
{
public ViewModel1()
{
// Test Data.
Items = new ObservableCollection<ItemViewModel>
{
new ItemViewModel{ Code = "001", Description = "Paint" },
new ItemViewModel{ Code = "002", Description = "Brush" },
new ItemViewModel{ Code = "003", Description = "" }
};
EditCommand = new CustomCommand<ItemViewModel>(Edit, CanEdit);
}
public CustomCommand<ItemViewModel> EditCommand { get; }
private bool CanEdit(ItemViewModel item)
{
return item?.Description != string.Empty;
}
private void Edit(ItemViewModel item)
{
Debug.WriteLine("Selected Item: {0} - {1}", item.Code, item.Description);
}
private ObservableCollection<ItemViewModel> _items { get; set; }
public ObservableCollection<ItemViewModel> Items
{
get => _items;
set
{
_items = value;
OnPropertyChanged();
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
XAML:
<Page x:Name="root"
x:Class="App1.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:vms="using:App1.ViewModels"
mc:Ignorable="d"
Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"
d:DesignHeight="450" d:DesignWidth="800">
<Page.DataContext>
<vms:ViewModel1 x:Name="Model"/>
</Page.DataContext>
<Grid>
<ItemsControl ItemsSource="{Binding Items}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel Margin="0 0 0 15">
<TextBlock Text="{Binding Code}" />
<TextBlock Text="{Binding Description}" />
<Button Content="Edit" Command="{Binding DataContext.EditCommand, ElementName=root}" CommandParameter="{Binding}" />
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
</Page>

I think you can pick a lot of code from the RelayCommand of MVVMLight. Try to change your event to
public event EventHandler CanExecuteChanged
{
add
{
if (canExecute != null)
{
CommandManager.RequerySuggested += value;
}
}
remove
{
if (canExecute != null)
{
CommandManager.RequerySuggested -= value;
}
}
}
and add also a function
public void RaiseCanExecuteChanged()
{
CommandManager.InvalidateRequerySuggested();
}
Then, whatever you put as your Predicate on the command, at the Predicate's boolean setter do:
SomeCustomCommand.RaiseCanExecuteChanged()
Hope I helped.

How to update listbox with progress bar GUI during execution

I have a listbox in a wpf window thats bound to a list in a viewmodel object. When I run a method in the viewmodel object it processes members of the list and each member has a progress. I would like to have the gui update continuously during execution. As it is now, it only updates gui when the processing is finished.
Here I have tried to create a small example of what I have right now:
MainWindow.xaml:
<Window x:Class="WPF_MVVM_Thread_Progressbar.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WPF_MVVM_Thread_Progressbar"
Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
<local:TestViewModel/>
</Window.DataContext>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="8*"/>
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="8*"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<ListBox Grid.Column="0" Grid.Row="0" Margin="5" ItemsSource="{Binding TestWorker.TestList}">
<ListBox.ItemContainerStyle>
<Style TargetType="{x:Type ListBoxItem}">
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
</Style>
</ListBox.ItemContainerStyle>
<ListBox.ItemTemplate>
<DataTemplate>
<Grid>
<ProgressBar Minimum="0" Maximum="100" Value="{Binding Progress, Mode=OneWay}" Background="Bisque">
<ProgressBar.Style>
<Style TargetType="{x:Type ProgressBar}">
<Style.Triggers>
<DataTrigger Binding="{Binding Progress}" Value="0">
<Setter Property="Visibility" Value="Hidden"/>
</DataTrigger>
</Style.Triggers>
</Style>
</ProgressBar.Style>
</ProgressBar>
<TextBlock FontWeight="Bold" Text="{Binding Path=Name}" Background="Transparent"/>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
<Button Grid.Column="0" Grid.Row="1" Content="TestRun" Command="{Binding TestRunCommand}"></Button>
<TextBlock Text="{Binding SelectedIdx}" Grid.Column="1" Grid.Row="1"/>
</Grid>
</Window>
MainWindowl.xaml.cs:
using Prism.Commands;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Windows;
namespace WPF_MVVM_Thread_Progressbar
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
}
public class TestViewModel : INotifyPropertyChanged
{
private WorkingClass _testWorker;
private DelegateCommand _testRunCommand;
public DelegateCommand TestRunCommand
{
get { return _testRunCommand; }
set { _testRunCommand = value; }
}
public WorkingClass TestWorker
{
get { return _testWorker; }
set { _testWorker = value; RaisePropertyChanged("TestWork"); }
}
private int _selectedIdx;
public int SelectedIdx
{
get { return _selectedIdx; }
set { _selectedIdx = value; RaisePropertyChanged("SelectedIdx"); }
}
public TestViewModel()
{
_testWorker = new WorkingClass();
_testRunCommand = new DelegateCommand(TestRun, canRun);
}
public async void TestRun()
{
//await Task.Run(() => _testWorker.Work());
_testWorker.Work();
}
private bool canRun()
{
return true;
}
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
public class WorkingClass : INotifyPropertyChanged
{
private ObservableCollection<TestObject> _testList;
public ObservableCollection<TestObject> TestList
{
get { return _testList; }
set { _testList = value; RaisePropertyChanged("TestList"); }
}
public WorkingClass()
{
_testList = new ObservableCollection<TestObject>();
_testList.Add(new TestObject("Object A"));
_testList.Add(new TestObject("Object B"));
_testList.Add(new TestObject("Object C"));
RaisePropertyChanged("TestList");
}
public void Work()
{
foreach (var obj in TestList)
{
obj.TestWork();
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
public class TestObject : INotifyPropertyChanged
{
private string _name;
public string Name
{
get { return _name; }
set { _name = value; }
}
private int _progress;
public int Progress
{
get { return _progress; }
set { _progress = value; RaisePropertyChanged("Progress"); }
}
public TestObject(string name)
{
this._name = name;
_progress = 0;
}
public void TestWork()
{
for (int i = 0; i < 100; i++)
{
System.Threading.Thread.Sleep(10);
Progress++;
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
}
I have tried to use ObservableCollection and INotifyPropertyChanged but this it seems not to be enough.
Eventually I would like to be able to have the same effect using async/await call from the TestViewModel.TestRun().
Could someone perhaps offer some insights on this? It would be much appreciated.

I think the current reason that you have the UI only updating once completed, is that you are running all of this on the UI thread. I would instead try this:
Task.Run(async delegate
{
await _testWorker.Work();
});
Or
Task.Run(() =>
{
_testWorker.Work();
});
Or
Task.Factory.StartNew(() =>
{
_testWorker.Work();
});
Or
var newThread = new Thread(new ThreadStart(_testWorker.Work());
newThread.Start();
This will return back to the UI instantly but allow your code to continue.
Note: You will have to be careful about the use of objects off the UI thread. ObservableCollections can only be created on the same thread as the dispatcher that handles the UI work. If you are using two-way binding, again you have to be careful about thread safety.

I've successfully done this in the past using a BackgroundWorker.
public class TestObject : INotifyPropertyChanged {
private BackgroundWorker worker;
public TestObject() {
worker = new BackgroundWorker() {
WorkerReportsProgress = true
};
worker.DoWork += DoWork;
worker.ProgressChanged += WorkProgress;
worker.RunWorkerCompleted += WorkFinished;
}
public int Progress
{
get { return _progress; }
set { _progress = value; RaisePropertyChanged("Progress"); }
}
// Begin doing work
public void TestWork() {
worker.RunWorkerAsync();
}
private void DoWork(object sender, DoWorkEventArgs eventArgs) {
worker.ReportProgress(0, "Work started");
for (int i = 0; i < 100; i++) {
System.Threading.Thread.Sleep(10);
worker.ReportProgress(i, "Message");
}
}
// Fires when the progress of a job changes.
private void WorkProgress(object sender, ProgressChangedEventArgs e) {
// Do something with the progress here
Progress = e.ProgressPercentage;
}
// Fires when a job finishes.
private void WorkFinished(object sender, RunWorkerCompletedEventArgs e) {
// The work finished. Do something?
}
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged(string propertyName)
{
// NOTE: If you're running C#6 use the null conditional operator for this check.
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(e));
}
}
A BackgroundWorker basically runs everything on a separate thread and reports back when its progress changes or it finishes working. You can pull out the ProgressPercentage from its progress report and use that in the UI. Hope that helps. To keep the example simple I didn't include some of your code but that should given you an idea of how it can be done.

How do I add item to a list when I select the item from a listview and click add button in the UI on WPF

I'm a newbie so excuse my question if it's too fade or if it's unclear.
any way, In my UI (WPF), i have a ListView that i created containing an observable collection of Type Collection = new ObservableCollection<type> and i have two Buttons "Add" & "Delete" I want to do this:
1-Whenever i select an item from my ListView in the UI(just click on it) , and click the "Add" button, the item is stored in a List called Scenario (Scenario = new List<type>).
2- Whenever i click the "Delete" button the Scenario list becomes empty.
I've tried something out but it doesn't work like it should, i can only add one item to the list Scenario and then it is blocked (when debugging) in
public bool CanExecute(object parameter)
{
return _canExecute == null || _canExecute(parameter);
}
Can someone tell me why? and how to fix it?
As for the "Delete" Button i didn't get to it yet because the other one doesn't work properly.
if you can propose a new solution or a solution for this problem i would be so thankful.
This is what i've done so far.
This is the code in the MainWindowModel :
private ObservableCollection<Type> _collection,_scenario;
public MainWindowModel()
{
Collection = new ObservableCollection<type>();
Scenario=new ObservableCollection<Type>();
DeleteCommand = new RelayCommand(o => DeleteExecute());
AddTypeCommand = new RelayCommand(o => AddTypeExecute());
}
private Type _isSelected;
public Type IsSelected;
{
get { return _isSelected; }
set
{
if (_isSelected != value)
{
_isSelected = value;
RaisePropertyChanged(nameof(IsSelected));
}
}
}
public ICommand DeleteCommand
{
get;
private set;
}
private RelayCommand _addTypeCommand;
public ICommand AddTypeCommand
{
get
{
if (_addTypeCommand == null)
{
_addTypeCommand = new RelayCommand(o => AddTypeExecute());
}
return _addTypeCommand;
}
set { }
}
private void DeleteExecute()
{
Scenario.Clear(); // Would this Work ?
}
private bool CanExecuteAddTypeCommand()
{
return true;
}
private void AddTypeExecute()
{
if (IsSelected != null)
{
Scenario.Add(IsSelected);
}
}
public ObservableCollection<Type> collection
{
get { return _collection; }
set { SetPropertyAndFireEvent(ref _collection, value); }
}
public ObservableCollection<Type> Scenario
{
get { return _scenario; }
set { SetPropertyAndFireEvent(ref _scenario, value); }
}
as for the MainWindowModel
<Window.DataContext>
<viewModels:MainWindowModel />
</Window.DataContext>
<Grid>
<ListView Grid.Row="2"
Grid.Column="0"
ItemsSource="{Binding Collection}"
SelectedItem="{Binding IsSelected}">
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}"/>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<Button Command="{Binding AddTypeCommand}"
Width="100"
Height="100"
Content="Add"
Grid.Row="0"
Grid.Column="2"/>
<Button Command="{Binding DeleteCommand}"
Content="Delete"
Width="100"
Height="100"
Grid.Row="2"
Grid.Column="2" />
</Grid>
As for the RelayCommand.cs
public class RelayCommand : ICommand
{
private readonly Action<object> _execute;
private readonly Func<object, bool> _canExecute;
//Notifies the Button bounded to the ICommand that the value returned by CanExecute has changed
public event EventHandler CanExecuteChanged
{
//raised whenever the commandmanager thinks that something has changed that will affect the ability of commands to execute
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
public RelayCommand(Action<object> execute, Func<object, bool> canExecute = null)
{
_execute = execute;
_canExecute = canExecute;
}
public bool CanExecute(object parameter)
{
return _canExecute == null || _canExecute(parameter);
}
public void Execute(object parameter)
{
_execute(parameter);
}
}

Try passing selectedItem as parameter for command,you dont pass anything and try to add...
name your ListView:
<ListView x:Name="listView"
and pass selectedItem as commandParameter
<Button Command="{Binding AddTypeCommand}"
CommandParameter="{Binding ElementName=listView, Path=SelectedItem}"
Width="100"
Height="100"
Content="Add"
Grid.Row="0"
Grid.Column="2" />
and then do your logic for adding, now you have parameter to add to your list.
EDIT: Here is some code that works, as i have understand that u need something like this.
ViewModel _> where all collection and command are created:
public class TestVM : INotifyPropertyChanged
{
public TestVM()
{
ListOne = new ObservableCollection<string>()
{
"str1","str2","str3"
};
// command
AddTypeCommand = new RelayCommand(OnAddExecute);
DeleteTypeCommand = new RelayCommand(OnDeleteExecuted);
}
private void OnDeleteExecuted()
{
ListTwo.Clear();
}
private void OnAddExecute()
{
if (SelectedItem != null)
{
ListTwo.Add(SelectedItem);
}
}
private string _selectedItem;
public string SelectedItem
{
get { return _selectedItem; }
set
{
if (_selectedItem != value)
{
_selectedItem = value;
OnPropertyChanged();
}
}
}
private ObservableCollection<string> _listOne;
public ObservableCollection<string> ListOne
{
get
{
return _listOne;
}
set
{
if (_listOne != value)
{
_listOne = value;
OnPropertyChanged();
}
}
}
public ObservableCollection<string> ListTwo { get; set; } = new ObservableCollection<string>();
public RelayCommand AddTypeCommand { get; private set; }
public RelayCommand DeleteTypeCommand { get; private set; }
public event PropertyChangedEventHandler PropertyChanged = delegate { };
public virtual void OnPropertyChanged([CallerMemberName] string propertyName = "")
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
RellayCommand how i implement it:
public class RelayCommand : ICommand
{
private Action _executeMethod;
private Func<bool> _canExecuteMethod;
#region RelayCommand ctor
public RelayCommand(Action executeMethod)
{
_executeMethod = executeMethod;
}
public RelayCommand(Action executeMethod, Func<bool> canExecuteMethod)
{
_executeMethod = executeMethod;
_canExecuteMethod = canExecuteMethod;
}
#endregion
public void RaiseCanExecuteChanged()
{
CanExecuteChanged(this, EventArgs.Empty);
}
#region ICommand Members
bool ICommand.CanExecute(object parameter)
{
if (_canExecuteMethod != null)
return _canExecuteMethod();
if (_executeMethod != null)
return true;
return false;
}
void ICommand.Execute(object parameter)
{
if (_executeMethod != null)
_executeMethod();
}
public event EventHandler CanExecuteChanged = delegate { };
#endregion
}
//--------------------------------------------------------------------------------------------
public class RelayCommand<T> : ICommand
{
private Action<T> _executeMethod;
private Func<T, bool> _canExecuteMethod;
#region RelayCommand ctor
public RelayCommand(Action<T> executeMethod)
{
_executeMethod = executeMethod;
}
public RelayCommand(Action<T> executeMethod, Func<T, bool> canExecuteMethod)
{
_executeMethod = executeMethod;
_canExecuteMethod = canExecuteMethod;
}
#endregion
public void RaiseCanExecuteChanged()
{
CanExecuteChanged(this, EventArgs.Empty);
}
#region ICommand Members
bool ICommand.CanExecute(object parameter)
{
var Tparam = (T)parameter;
if (_canExecuteMethod != null)
return _canExecuteMethod(Tparam);
if (_executeMethod != null)
return true;
return false;
}
void ICommand.Execute(object parameter)
{
if (_executeMethod != null)
_executeMethod((T)parameter);
}
public event EventHandler CanExecuteChanged = delegate { };
#endregion
}
And MainWindow.xaml just to show purpose. Selecting on one item in 1rst list and pressing button Add will add it to second ListView. DeleteButton will clear second list.
<Window x:Class="WpfApp5.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApp5"
mc:Ignorable="d"
Title="MainWindow"
Height="350"
Width="525">
<Window.DataContext>
<local:TestVM />
</Window.DataContext>
<Grid>
<ListView x:Name="listViewOne"
ItemsSource="{Binding ListOne}"
SelectedItem="{Binding SelectedItem,Mode=TwoWay}"
Width="100"
Height="200"
Margin="17,17,400,105" />
<ListView x:Name="listViewTwo"
ItemsSource="{Binding ListTwo}"
Width="100"
Height="200"
Margin="339,17,78,105" />
<Button Command="{Binding AddTypeCommand}"
Content="Add"
Grid.Row="0"
Margin="208,111,198,178" />
<Button Command="{Binding DeleteTypeCommand}"
Content="Delete"
Grid.Row="0"
Margin="208,157,198,132" />
</Grid>
</Window>