Question

I have an object that is created, and want to bind to a property of that object through the mode OneWayToSource explicitly. This binding however is not working at all. It also has a red border around the textbox right when the program is initialized, when I only want the input validated once I click the button. My last ditch effor was embedding the source to the element itself, but no such luck. Here is what I have:

<StackPanel.Resources>
    <my:HoursWorked x:Key="hwViewSource" /> 
</StackPanel.Resources>

<TextBox Style="{StaticResource textBoundStyle}" Name="adminTimeTxtBox">
    <Binding Source="{StaticResource hwViewSource}" Path="Hours" UpdateSourceTrigger="PropertyChanged" Mode="OneWayToSource">
        <Binding.ValidationRules>
            <my:NumberValidationRule ErrorMessage="Please enter a number in hours." />
        </Binding.ValidationRules>
    </Binding>
</TextBox>

The HoursWorked object looks like this:

//I have omitted a lot of things so it's more readable
public class HoursWorked : INotifyPropertyChanged
{

    private double hours;

    public HoursWorked()
    {
        hours = 0;
    }

    public double Hours
    {
        get { return hours; }
        set 
        {
            if (Hours != value)
            {
                hours = value;
                OnPropertyChanged("Hours");
            }
        }
    }

    #region Databinding
    public event PropertyChangedEventHandler PropertyChanged;
    private void OnPropertyChanged(String info)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(info));
        }
    }
    #endregion
}

once the window is initialized, this is the portion of code I have:

public partial class Blah : Window
{
     private HoursWorked newLog;

public Blah()
{
    InitializeComponent();
    newLog = new HoursWorked();
    adminTimeTxtBox.DataContext = newLog;
}

private void addAdBtn_Click(object sender, RoutedEventArgs e)
{
    AddHours();

}

private void AddHours()
{
    if (emp.UserType.Name == "Admin")
    {
        if(!ValidateElement.HasError(adminTimeTxtBox))
        {
                item.TimeLog.Add(newLog);
                UpdateTotals();
                adminTimeTxtBox.Clear();
        }
         }

    }
}

and finally ValidateElement looks like this:

public static class ValidateElement
{
    public static bool HasError(DependencyObject node)
    {
        bool result = false;
        if (node is TextBox)
        {
            TextBox item = node as TextBox;
            BindingExpression be = item.GetBindingExpression(TextBox.TextProperty);
            be.UpdateSource();
        }
        if (Validation.GetHasError(node))
        {
            // If the dependency object is invalid, and it can receive the focus,
            // set the focus
            if (node is IInputElement) Keyboard.Focus((IInputElement)node);
            result = true;
        }

        return result;

    }
}

It validates properly, but every time I check to see if the property updates, it doesn’t. I really need help on this, any help would be greatly appreciated.

Answer 1

You’ve got 2 instances of the HoursWorked class.

One is created in Resources via this tag <my:HoursWorked x:Key="hwViewSource" /> but then you create one in your Window with newLog = new HoursWorked(); and set it into the DataContext of the adminTimeTxtBox…so the one your Binding to (the Resource one) isn’t the same as the one you’re updating (the one inside Window).

You could change the Binding to

<Binding Source="{Binding}" ….

and then don’t need the one defined in Resource.