class property databinding

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Hi, I have got a Task class:

C#

public class Task : INotifyPropertyChanged
{
    private string taskName;
    private string description;
    public string Description
    {
        get { return description; }
        set
        {
            description = value;
            OnPropertyChanged(new PropertyChangedEventArgs("Description"));
        }
    }

    public string TaskName
    {
        get { return taskName; }
        set
        {
            taskName = value;
            OnPropertyChanged(new PropertyChangedEventArgs("TaskName"));
        }

    }
    private ObservableCollection<Task> subTasks;
    public ObservableCollection<Task> SubTasks
    {
        get { return subTasks; }
        set
        {
            subTasks = value;
            OnPropertyChanged(new PropertyChangedEventArgs("SubTasks"));
        }
    }
    public event PropertyChangedEventHandler PropertyChanged;
    public void OnPropertyChanged(PropertyChangedEventArgs e)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, e);
    }
    //ctors
    public Task(string strTaskName)
    {
        TaskName = strTaskName;
        //SubTasks = new ObservableCollection<Task>();
    }
    public Task(string strTaskName, string strDescription)
    {
        TaskName = strTaskName;
        Description = strDescription;
        //SubTasks = new ObservableCollection<Task>();
    }

    public Task(string strTaskName, ObservableCollection<Task> subs)
    {
        TaskName = strTaskName;
        SubTasks = subs;
    }
}

that needs its Description property bound to a textbox control with this XAML:

HTML

<Window x:Class="Task_it.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">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition></ColumnDefinition>
            <ColumnDefinition></ColumnDefinition>
        </Grid.ColumnDefinitions>
        <TreeView Name="treeTasks" Grid.Column="1" Margin="5">
            <TreeView.ItemTemplate>
                <HierarchicalDataTemplate ItemsSource="{Binding Path=SubTasks}">
                    
                    <TextBlock Text="{Binding Path=TaskName}" />
                    
                </HierarchicalDataTemplate>               
            </TreeView.ItemTemplate>
        </TreeView>

        <TextBox  Name="txtDescription" Grid.Column="0" VerticalAlignment="Top" Margin="5" Text="{Binding Path=Description}">     
        </TextBox>
            
       
    </Grid>
</Window>

I am new to WPF and I dont know where the problem occurs that the text box is not showing the description. And this is the main window:

C#

InitializeComponent();
Task job11 = new Task("JOB 1.1","This is job 1.1");
            Task job12 = new Task("JOB 1.2", "This is job 1.2");
            Task job13 = new Task("JOB 1.3", "This is job 1.3");
            Task job14 = new Task("JOB 1.4","This is job 1.4");
            Task MainTask = new Task("Main Job", new ObservableCollection<Task>(new List<Task> { job11, job12, job13, job14 }));
            MainTask.Description = "This is my dear MAINTASK";
txtDescription.DataContext = MainTask;
 treeTasks.Items.Add(MainTask);
            treeTasks.FlowDirection = System.Windows.FlowDirection.RightToLeft;

Posted 16-Oct-12 5:10am

cs101000

Updated 16-Oct-12 5:46am

v2

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Comments

[no name] 16-Oct-12 11:14am

And so why are you reposting this?

cs101000 16-Oct-12 11:24am

I didnt get my answer and Im going to delete the previous one.

[no name] 16-Oct-12 11:26am

So? Why? You did your answer, you did not set the datacontext. You know what the problem is, why don't you go off and fix it?

cs101000 16-Oct-12 11:33am

What I inferred from that is I have to set the datacontext in main window ctor like this:
txtDescription.DataContext = MainTask;

which is not working.

[no name] 16-Oct-12 11:36am

Did you try DataContext = new Task()? What is "MainTask"? What error messages to you see int he debug window?

cs101000 16-Oct-12 11:47am

Take a look at the improved part please. I dont get any error messages.

1 solution

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Clifford Nelson · Accepted Answer · 2012-10-16T08:50:00

Unfortunately there is no SelectedItem read/write dependency property for WPF. You can create a behaviour to get around this (http://stackoverflow.com/questions/1000040/selecteditem-in-a-wpf-treeview[^]), or use code behind for the SelectedItemChanged.

Ideally you should have a view model with an ItemsSource and SelectedItem property, and bind to each. The quick fix is to used the SelectedItemChanged event, and set the Text property of the TextBox to the Description of the new selected item:

C#

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        InitializeComponent();
        Task job11 = new Task("JOB 1.1", "This is job 1.1");
        Task job12 = new Task("JOB 1.2", "This is job 1.2");
        Task job13 = new Task("JOB 1.3", "This is job 1.3");
        Task job14 = new Task("JOB 1.4", "This is job 1.4");
        Task MainTask = new Task("Main Job", new ObservableCollection<Task>(new List<Task> { job11, job12, job13, job14 }));
        MainTask.Description = "This is my dear MAINTASK";
        txtDescription.DataContext = MainTask;
        treeTasks.Items.Add(MainTask);
        treeTasks.FlowDirection = System.Windows.FlowDirection.RightToLeft;

        treeTasks.SelectedItemChanged += new RoutedPropertyChangedEventHandler<object>(treeTasks_SelectedItemChanged);
    }

    void treeTasks_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
    {
        var task = (Task) e.NewValue;
        txtDescription.Text = task.Description;
    }

class property databinding

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class property databinding

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