Develop Reference

ListView Item Source is null on initialization

I am trying to use a filter for a ListView upon and on initialization, the project is throwing a Null Pointer for the ListView, even though I am setting it in the Constructor and the binding. Here is my code:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
var viewModel = new MainViewModel();
this.ProjectListView.ItemsSource = viewModel.Projects;
And here is the XAML that refernces it.
<ListView x:Name="ProjectListView" Margin="0,0,10,0" ItemsSource="{Binding Projects}" FontSize="16" Foreground="Black">
I am not sure why the ItemSource is null if it is initialized in the Constructor. Is there a PropertyChanged binding I need to apply?
Here's most of my XAML
<TextBox x:Name="FolderNameBox" Grid.Column="1" Background="White" Grid.Row="1" Grid.ColumnSpan="5"
Margin="0,0,287,654.333" VerticalContentAlignment="Center"
Padding="6" FontSize="16"
IsReadOnly="True"
Text="{Binding ElementName=Hierarchy, Path=SelectedItem.Path, UpdateSourceTrigger=PropertyChanged, Mode=OneWay}">
</TextBox>
<TextBox x:Name="SearchProjectsBox" Grid.Column="5" Background="White" Grid.Row="1" Text="Search Projects"
Margin="47.333,0,0,654.333" VerticalContentAlignment="Center" Foreground="LightGray" Padding="6" FontSize="16" HorizontalAlignment="Left" Width="268" GotFocus="TextBox_GotFocus" LostFocus="TextBox_LostFocus" TextChanged="FilterListView"/>
<TreeView x:Name="Hierarchy" Grid.Column="4" HorizontalAlignment="Left" Height="631" Margin="0,58,0,0" Grid.Row="1" VerticalAlignment="Top" Width="226"
ItemsSource="{Binding Path=Projects}">
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding ChildFolders}">
<StackPanel Orientation="Horizontal" >
<Image Source="{Binding Icon}" Margin="5, 5, 5, 5"></Image>
<TextBox Text="{Binding Name, UpdateSourceTrigger=PropertyChanged}" BorderThickness="0" FontSize="16" Margin="5" IsReadOnly="True" PreviewMouseDoubleClick="SelectAll" LostFocus="TextBoxLostFocus"/>
</StackPanel>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
<Grid Grid.ColumnSpan="2" Grid.Column="4" HorizontalAlignment="Left" Height="631" Margin="245,58,0,0" Grid.Row="1" VerticalAlignment="Top" Width="540">
<ScrollViewer HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden">
<ListView x:Name="ProjectListView" Margin="0,0,10,0" ItemsSource="{Binding Projects}" FontSize="16" Foreground="Black">
<ListView.ItemContainerStyle>
<Style TargetType="{x:Type ListViewItem}">
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="true">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="BorderBrush" Value="Transparent"/>
</Trigger>
<Trigger Property="IsMouseOver" Value="false">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="BorderBrush" Value="Transparent"/>
</Trigger>
</Style.Triggers>
</Style>
</ListView.ItemContainerStyle>
ANd heres my base View Model
private ObservableCollection<Project> projects;
public ObservableCollection<Project> Projects
{
get { return projects; }
set
{
if (value != projects)
{
projects = value;
OnPropertyChanged("Projects");
}
}
}
This is the Code Behind
public MainWindow()
{
InitializeComponent();
DataContext = new MainViewModel();
MainViewModel model = new MainViewModel();
model.BuildData();
this.ProjectListView.ItemsSource = model.Projects;
}
private void FilterListView(object sender, TextChangedEventArgs e)
{
CollectionViewSource.GetDefaultView(this.ProjectListView.ItemsSource).Refresh();
}
FilterListView is the TextChange method. It breaks on the first line. ProjectListVIew is registering as null but it shouldn't even be launched because it is dependent on a change in the TextBox.
Edit. Here's the code behind
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = new MainViewModel();
MainViewModel model = new MainViewModel();
model.BuildData();
this.ProjectListView.ItemsSource = model.Projects;
}
private void FilterListView(object sender, TextChangedEventArgs e)
{
CollectionViewSource.GetDefaultView(this.ProjectListView.ItemsSource).Refresh();
}
private void SelectAll(object sender, MouseButtonEventArgs e)
{
TextBox box = sender as TextBox;
box.IsReadOnly = false;
box.SelectAll();
}
private void TextBoxLostFocus(object sender, RoutedEventArgs e)
{
TextBox box = sender as TextBox;
box.IsReadOnly = true;
}
private void TextBox_GotFocus(object sender, RoutedEventArgs e)
{
TextBox tb = (TextBox)sender;
tb.Text = string.Empty;
tb.Foreground = Brushes.Black;
tb.GotFocus -= TextBox_GotFocus;
}
private void TextBox_LostFocus(object sender, RoutedEventArgs e)
{
TextBox box = (TextBox)sender;
box.Text = "Search Projects";
box.Foreground = Brushes.LightGray;
box.GotFocus += TextBox_GotFocus;
}
}
}
Base View Model
public class ViewModelBase : INotifyPropertyChanged
{
#region INotifyPropertyChanged
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string projectName)
{
var handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(projectName));
}
}
#endregion INotifyPropertyChanged
}
And the View Model I am using
class MainViewModel : ViewModelBase
{
private ObservableCollection<Project> projects;
public ObservableCollection<Project> Projects
{
get { return projects; }
set
{
if (value != projects)
{
projects = value;
OnPropertyChanged("Projects");
}
}
}
EDIT:
My ListView constantly changes - as in, the data shown will be based on a User's selection in a TreeView. Right now, my filter doesn't take into consideration what is actually on the screen. It is only filtering based on the binded Collection.
So if my Collection is Fruit, Vegetables, Meat, Dairy and my ListView is Apple, Carrot, and Milk, if I search Apple, the ListView will be blank but if I search Fruit, I will have a populated row. Not correcty, clearly.
Sounds like I am fairly close.
This is my View Model:
public ICollectionView SourceCollection
{
get
{
return this.projectCollection.View;
}
}
public string FilterText
{
get
{
return filterText;
}
set
{
filterText = value;
this.projectCollection.View.Refresh();
RaisePropertyChanged("SearchProjectsText");
}
}
private void projectCollection_Filter(object sender, FilterEventArgs e)
{
if (string.IsNullOrEmpty(FilterText))
{
e.Accepted = true;
return;
}
Project project = e.Item as Project;
if (project.Name.ToUpper().Contains(FilterText.ToUpper()) || project.Path.ToUpper().Contains(FilterText.ToUpper()))
{
e.Accepted = true;
}
else
{
e.Accepted = false;
}
}
public void RaisePropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Where SearchProjectText is the actual TextBox used for filtering. My relevant XAML:
<TextBox x:Name="SearchProjectsBox" Grid.Column="5" Background="White" Grid.Row="1" Text="{Binding FilterText, UpdateSourceTrigger=PropertyChanged}"
Margin="47.333,0,0,654.333" VerticalContentAlignment="Center" Foreground="Black" Padding="6" FontSize="16" HorizontalAlignment="Left" Width="268"/>
<TreeView x:Name="Hierarchy" Grid.Column="4" HorizontalAlignment="Left" Height="631" Margin="0,58,0,0" Grid.Row="1" VerticalAlignment="Top" Width="226"
ItemsSource="{Binding Path=Projects}">
<ListView x:Name="ProjectListView" Margin="0,0,10,0" ItemsSource="{Binding SourceCollection}" FontSize="16" Foreground="Black">

You never set the datacontext. Don't both bind and assign; you don't need both. Just set the DataContext of the parent, and bind the appropriate parent property in the XAML (which you already did -- your XAML looks fine):
public MainWindow()
{
InitializeComponent();
DataContext = new MainViewModel();
}
And make sure your viewmodel properly raises INotifyPropertyChanged.PropertyChanged when you assign a new collection instance to its Projects property.
And make sure you do give Projects a collection, and that there's something in it.
You're using ObservableCollection<T> I hope, not List<T>, for the collection?
Update
I don't know why (it's late and I'm tired, sorry!), but FilterListView is getting called before InitializeComponent(). I should've thought of that when you described the symptoms. This fixes it for me:
private void FilterListView(object sender, TextChangedEventArgs e)
{
if (this.ProjectListView != null)
{
CollectionViewSource.GetDefaultView(this.ProjectListView.ItemsSource).Refresh();
}
}

set the DataContext that will create a new instance of the ViewModel it's binding to.
public MainWindow()
{
InitializeComponent();
DataContext = new MainViewModel();
}

WPF: DataTrigger not firing

In a WPF Project I have some restyled DataGridColumnHeaders of a DataGrid which show a ComboBox for each DataGridColumnHeader. When the user selects from the ComboBox's the SelectionChanged handler (in the code behind) updates an Array of ColumnOptionViewModel objects on the MainWindowViewModel with the newest selection.
At this point some code also works out if there are any duplicate selections in this array, and then sets an IsDuplicate Boolean property on the ColumnOptionViewModel that are duplicates. The idea is that a DataTrigger picks up the change in IsDuplicate and changes the Background of a TextBlock in the DataTemplate of the ItemTemplate for the duplicate ComboBox's to Red.
However, this trigger is not firing. The IsDuplicate properties are being set ok, and everything else works as expected. What am I doing wrong?
Here is the XAML for the Window:
<Window x:Class="TestDataGrid.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:TestDataGrid"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525">
<Grid>
<DataGrid Grid.Row="1" x:Name="dataGrid" ItemsSource="{Binding Records}">
<DataGrid.ColumnHeaderStyle>
<Style TargetType="DataGridColumnHeader">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<StackPanel>
<ComboBox x:Name="cbo"
ItemsSource="{Binding RelativeSource={RelativeSource AncestorType={x:Type DataGrid}},Path=DataContext.ColumnOptions}"
SelectionChanged="cbo_SelectionChanged">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock x:Name="txt" Text="{Binding Name}"/>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding ElementName=cbo, Path=SelectedItem.IsDuplicate}">
<Setter TargetName="txt" Property="Background" Value="Red"/>
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
</StackPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</DataGrid.ColumnHeaderStyle>
</DataGrid>
</Grid>
CODE BEHIND:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
this.DataContext = new MainWindowViewModel(RecordProvider.GetRecords());
}
private void cbo_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
var vm = (MainWindowViewModel)DataContext;
var selectionChangedCombo = (ComboBox)e.Source;
var dataGridColumnHeader = selectionChangedCombo.TemplatedParent as DataGridColumnHeader;
vm.ColumnSelections[dataGridColumnHeader.DisplayIndex] = selectionChangedCombo.SelectedItem as ColumnOptionViewModel;
CheckForDuplicates();
}
private void CheckForDuplicates()
{
var vm = (MainWindowViewModel)DataContext;
var duplicates = vm.ColumnSelections.GroupBy(x => x.Name)
.Where(g => g.Skip(1).Any())
.SelectMany(g => g);
foreach (var option in duplicates)
{
option.IsDuplicate = true;
}
}
}
MainWindowViewModel :
public class MainWindowViewModel : ViewModelBase
{
public ObservableCollection<ColumnOptionViewModel> _columnOptions = new ObservableCollection<ColumnOptionViewModel>();
public ObservableCollection<RecordViewModel> _records = new ObservableCollection<RecordViewModel>();
ColumnOptionViewModel[] _columnSelections = new ColumnOptionViewModel[3];
public MainWindowViewModel(IEnumerable<Record> records)
{
foreach (var rec in records)
{
Records.Add(new RecordViewModel(rec));
}
ColumnOptions.Add(new ColumnOptionViewModel(TestDataGrid.ColumnOptions.ColumnOption1));
ColumnOptions.Add(new ColumnOptionViewModel(TestDataGrid.ColumnOptions.ColumnOption2));
ColumnOptions.Add(new ColumnOptionViewModel(TestDataGrid.ColumnOptions.ColumnOption3));
ColumnSelections[0] = ColumnOptions[0];
ColumnSelections[1] = ColumnOptions[1];
ColumnSelections[2] = ColumnOptions[2];
}
public ObservableCollection<ColumnOptionViewModel> ColumnOptions
{
get { return _columnOptions; }
set { _columnOptions = value; }
}
public ColumnOptionViewModel[] ColumnSelections
{
get { return _columnSelections; }
set { _columnSelections = value; }
}
public ObservableCollection<RecordViewModel> Records
{
get { return _records; }
set { _records = value; }
}
}
ColumnOptionViewModel :
public class ColumnOptionViewModel : ViewModelBase
{
ColumnOptions _colOption;
public ColumnOptionViewModel(ColumnOptions colOption )
{
_colOption = colOption;
}
public string Name
{
get { return _colOption.ToString(); }
}
public override string ToString()
{
return Name;
}
private bool _isDuplicate = false;
public bool IsDuplicate
{
get { return _isDuplicate; }
set
{ _isDuplicate = value;
OnPropertyChanged();
}
}
}
EDIT:
ViewModelBase :
public abstract class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}

If you are trying to bind to the IsDuplicate property of the SelectedItem in the ComboBox you could use a RelativeSource.
You should also set the Value property of the DataTrigger to true/false depending on when you want the Background property of the TextBlock to be set to Red:
<ComboBox x:Name="cbo" ItemsSource="{Binding RelativeSource={RelativeSource AncestorType={x:Type DataGrid}},Path=DataContext.ColumnOptions}"
SelectionChanged="cbo_SelectionChanged">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock x:Name="txt" Text="{Binding Name}"/>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding Path=SelectedItem.IsDuplicate, RelativeSource={RelativeSource AncestorType=ComboBox}}" Value="True">
<Setter TargetName="txt" Property="Background" Value="Red"/>
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>

As #mm8 said, the Value is not chosen in your DataTrigger.
If that doesn't work, you can try using Trigger directly on TextBlock instead of DataTemplate.Triggers:
<TextBlock>
<TextBlock.Style>
<Style TargetType="TextBlock">
<Setter Property="Background" Value="White"/>
<Style.Triggers>
<DataTrigger Binding="{Binding Path=IsDuplicate}" Value="True">
<Setter Property="Background" Value="Red"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
Also, background and foreground values in controls that have selectable items can be tricky. For example, you may want to disable default selection colors (unfortunately then you will have to manage selected/focused background yourself):
<ComboBox.Resources>
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="Transparent" />
</ComboBox.Resources>

Refresh ListView item with Image's Source bound to property

I have problem with refreshing my listview data. It doesn't update unless I call:
List.ItemsSource = null;
List.ItemsSource = listviewSource;
This is works but doesn't look good (screen flashes) so I wanted to use, as people suggested, INotifyPropertyChanged.
My listviewSource is ObservableCollection< Class2> where Class2 implements Class1 and Class1 implements INotifyPropertyChanged.
public class Class1 : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void NotifyPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
...
}
public class Class2 : Class1
{
private string ImgSource;
public string imgSource
{
get { return this.ImgSource; }
set
{
this.ImgSource = value;
NotifyPropertyChanged("imgSource");
}
}
....
}
imgSource is binded to ListView but when it changes nothing happens... Am I doing something wrong?
XAML markup
<ListView x:Name="List" Width="400" HorizontalAlignment="Center" Loaded="List_Loaded">
<ListView.ItemContainerStyle>
<Style TargetType="ListViewItem">
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
<Setter Property="VerticalContentAlignment" Value="Top"/>
<Setter Property="HorizontalAlignment" Value="Stretch"/>
<Setter Property="VerticalAlignment" Value="Top"/>
</Style>
</ListView.ItemContainerStyle>
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel Tag="{Binding number}" Background="#FF0E1D23" Margin="0,5" >
<Image Margin="339,10,23,13" Source="{Binding imgSource}"/>
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>

It seems that Image's Source default binding mode is OneTime.
Change it explicitly to OneWay:
Source="{Binding imgSource, Mode = OneWay}"

Bind Button IsEnabled property to DataTemplate items state and one additional condition

I have an object with editable parameters collection which are bound as a ItemsSource to ItemsControl, and a property which checks if all parameter values are ok. This property bound to button's IsEnabled.
I also want to disable the button when any of textbox has validation error (Validation.HasError == true).
Thanks in advance.
XAML:
<Window x:Class="MyWPFTest.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<StackPanel>
<ItemsControl ItemsSource="{Binding Path=MyObject.Parameters}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Path=Name}"></TextBlock>
<TextBox Text="{Binding Path=Value, UpdateSourceTrigger=PropertyChanged}"></TextBox>
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
<Button IsEnabled="{Binding Path=MyObject.IsParametersOkay}">OK</Button>
</StackPanel>
</Window>
Code:
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Windows;
namespace MyWPFTest
{
public partial class MainWindow : Window
{
ObjectWithParameters _MyObject = new ObjectWithParameters();
public ObjectWithParameters MyObject { get { return _MyObject; } }
public MainWindow()
{
InitializeComponent();
DataContext = this;
}
}
public class ObjectWithParameters : INotifyPropertyChanged
{
ObservableCollection<Parameter> _Parameters = new ObservableCollection<Parameter>();
public ObservableCollection<Parameter> Parameters { get { return _Parameters; } }
public event PropertyChangedEventHandler PropertyChanged;
public ObjectWithParameters()
{
var p1 = new Parameter("Parameter 1", 0); p1.PropertyChanged += ParameterChanged; Parameters.Add(p1);
var p2 = new Parameter("Parameter 2", 0); p2.PropertyChanged += ParameterChanged; Parameters.Add(p2);
}
void ParameterChanged(object sender, PropertyChangedEventArgs e)
{
if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("IsParametersOkay"));
}
public bool IsParametersOkay
{
get { return Parameters.FirstOrDefault(p => p.Value < 0) == null; }
}
}
public class Parameter : INotifyPropertyChanged
{
double val;
public double Value
{
get { return val; }
set { val = value; if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("Value")); }
}
public string Name { get; set; }
public event PropertyChangedEventHandler PropertyChanged;
public Parameter(string name, double value) { Name = name; Value = value; }
}
}

Check out MultiTriggers.
<Style.Triggers>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Background" Value="#EEEEEE" />
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="HasItems" Value="false" />
<Condition Property="Width" Value="Auto" />
</MultiTrigger.Conditions>
<Setter Property="MinWidth" Value="120"/>
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="HasItems" Value="false" />
<Condition Property="Height" Value="Auto" />
</MultiTrigger.Conditions>
<Setter Property="MinHeight" Value="95"/>
</MultiTrigger>
</Style.Triggers>

This is the way I solved the problem. May be it's not a very elegant solution, but it works.
I added a new property IsFormOkay to MainWindow class, which checks both controls and parameters validity. Then I bound Button.IsEnabled to this property and added TextChanged event for TextBox to notify about IsFormOkay.
Here is code added to MainWindow:
public event PropertyChangedEventHandler PropertyChanged;
public bool IsFormOkay { get { return IsValid(Items) && MyObject.IsParametersOkay; } }
public bool IsValid(DependencyObject obj)
{
if (Validation.GetHasError(obj)) return false;
for (int i = 0, n = VisualTreeHelper.GetChildrenCount(obj); i < n; i++)
{
DependencyObject child = VisualTreeHelper.GetChild(obj, i);
if (!IsValid(child)) return false;
}
return true;
}
private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
{
if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("IsFormOkay"));
}
And changes to XAML:
<StackPanel>
<ItemsControl x:Name="Items" ItemsSource="{Binding Path=MyObject.Parameters}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Path=Name}" />
<TextBox TextChanged="TextBox_TextChanged" Text="{Binding Path=Value, UpdateSourceTrigger=PropertyChanged}" />
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
<Button IsEnabled="{Binding Path=IsFormOkay}" Content="OK" />
</StackPanel>

Data Binding Not Working Properly

In this program, I'm able to add one tab at a time by clicking the "Add Course" button. Ideally, the header of the tab should be the course name I entered and the text in the textbox , which is on the tab, should display the course name.
However, it's not functioning correctly. When I tried to add more than 1 tabs, each time it gives me this error message:
System.Windows.Data Error: 40 : BindingExpression path error: 'Text' property not found on 'object' ''MyHomeworkViewModel' (HashCode=33010577)'. BindingExpression:Path=Text; DataItem='MyHomeworkViewModel' (HashCode=33010577); target element is 'TextBox' (Name=''); target property is 'Text' (type 'String')
Also, it seems to "override" other tab's text (just text, not header). For example, if I add a tab with header "a", the text of that is also "a". Then if I add "B", both textboxes on two tabs become "B". However, if I print out the Text property of each tab (MyHomeworkModel in this case), they are "a" and "B", respectively.
I have been debugging this whole day but no luck. Any help would be appreciated!
My View (DataContext set to MyHomeworkViewModel):
<Window x:Class="MyHomework__MVVM_.MyHomeworkView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="My Homework" Height="450" Width="800" ResizeMode="CanMinimize">
<Grid Margin="0,0,10,10">
<TabControl HorizontalAlignment="Left" Height="330" VerticalAlignment="Top" Width="764" Margin="10,10,0,0" ItemsSource="{Binding AllTabs}" SelectedItem="{Binding SelectedTab}">
<TabControl.ItemContainerStyle>
<Style TargetType="TabItem">
<Setter Property="Header" Value="{Binding Header}"/>
<Setter Property="Content">
<Setter.Value>
<Grid>
<TextBox Text="{Binding Text}" FontSize="16" AcceptsReturn="True" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
</TextBox>
</Grid>
</Setter.Value>
</Setter>
<Setter Property="FontSize" Value="20"/>
</Style>
</TabControl.ItemContainerStyle>
</TabControl>
<Button Content="Add Course" HorizontalAlignment="Left" VerticalAlignment="Top" Width="105" Margin="10,351,0,0" Height="50" Command="{Binding AddCourseCommand}"/>
<Button Content="Drop Course" HorizontalAlignment="Left" VerticalAlignment="Top" Width="76" Margin="138,379,0,0" Height="22" Command="{Binding DropCourseCommand, UpdateSourceTrigger=PropertyChanged}"/>
<Button Content="Save HW" HorizontalAlignment="Left" VerticalAlignment="Top" Width="105" Margin="669,351,0,0" Height="50"/>
</Grid>
</Window>
My Model:
using System.ComponentModel;
namespace MyHomework__MVVM_
{
class MyHomeworkModel : INotifyPropertyChanged
{
private string header, text;
public event PropertyChangedEventHandler PropertyChanged;
public string Header
{
get
{
return header;
}
set
{
header = value;
OnPropertyChanged("Header");
}
}
public string Text
{
get
{
return text;
}
set
{
text = value;
OnPropertyChanged("Text");
}
}
private void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
}
My ViewModel:
using MyHomework;
using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Windows.Input;
namespace MyHomework__MVVM_
{
class MyHomeworkViewModel : INotifyPropertyChanged
{
private ObservableCollection<MyHomeworkModel> allTabs;
private MyHomeworkModel selectedTab;
private MyHomeworkView mainWindow;
public event PropertyChangedEventHandler PropertyChanged;
public MyHomeworkViewModel(MyHomeworkView mainWindow)
{
allTabs = new ObservableCollection<MyHomeworkModel>();
this.mainWindow = mainWindow;
AddCourseCommand = new AddCourseCommand(this);
DropCourseCommand = new DropCourseCommand(this);
}
public ObservableCollection<MyHomeworkModel> AllTabs
{
get
{
return allTabs;
}
set
{
allTabs = value;
OnPropertyChanged("AllTabs");
}
}
public MyHomeworkModel SelectedTab
{
get
{
return selectedTab;
}
set
{
selectedTab = value;
OnPropertyChanged("SelectedTab");
}
}
public ICommand AddCourseCommand
{
get;
private set;
}
public ICommand DropCourseCommand
{
get;
private set;
}
public void AddNewTab()
{
NewCourseName ncn = new NewCourseName();
ncn.Owner = mainWindow;
ncn.ShowDialog();
if (ncn.courseName != null)
{
MyHomeworkModel newTab = new MyHomeworkModel();
newTab.Header = ncn.courseName;
newTab.Text = ncn.courseName;
AllTabs.Add(newTab);
SelectedTab = newTab;
}
foreach (MyHomeworkModel item in AllTabs)
{
Console.WriteLine(item.Text);
}
}
public bool CanDrop()
{
return SelectedTab != null;
}
public void RemoveTab()
{
DropCourseConfirmation dcc = new DropCourseConfirmation();
dcc.Owner = mainWindow;
dcc.ShowDialog();
if (dcc.drop == true)
{
int index = AllTabs.IndexOf(SelectedTab);
AllTabs.Remove(SelectedTab);
if (AllTabs.Count > 0)
{
if (index == 0)
{
SelectedTab = AllTabs[0];
}
else
{
SelectedTab = AllTabs[--index];
}
}
else
{
SelectedTab = null;
}
}
}
private void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
}
Please let me know if you need more codes to help me.

Change your
<Setter Property="Content">
<Setter.Value>
<Grid>
<TextBox Text="{Binding Text}" FontSize="16" AcceptsReturn="True" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
</TextBox>
</Grid>
</Setter.Value>
</Setter>
for this:
<Setter Property="ContentTemplate">
<Setter.Value>
<DataTemplate>
<Grid>
<TextBox Text="{Binding Text}" FontSize="16" AcceptsReturn="True" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
</TextBox>
</Grid>
</DataTemplate>
</Setter.Value>
</Setter>

Your DataContext isn't what you think it is. Read the error there. It states that "Text" is not a valid property on MyHomeworkViewModel which is true (As opposed to your MyHomeworkModel).
What you need to be modifying instead of the ItemContainerStyle is instead the ItemTemplate and the ContentTemplate which uses the appropriate object within your ItemsSource as its DataContext.
Additionally, the binding in your TextBox needs to be Text="{Binding Text, Mode=TwoWay}" or it won't modify the property in your model.