Question

I am writing the test application in Windows Forms. It has a simple form with TextBox and needs to implement DataBinding. I have implemented the class FormViewModel to hold my data, and have 1 class for my business data — TestObject.

Business Data object:

public class TestObject : INotifyPropertyChanged
{
    private string _testPropertyString;
    public string TestPropertyString
    {
        get
        {
            return _testPropertyString;
        }
        set
        {
            if (_testPropertyString != value)
            {
                _testPropertyString = value;
                RaisePropertyChanged("TestPropertyString");
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public void RaisePropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

ViewModel:

public class FormViewModel : INotifyPropertyChanged
{
    private TestObject _currentObject;
    public TestObject CurrentObject
    {
        get { return _currentObject; }
        set
        {
            if (_currentObject != value)
            {
                _currentObject = value;

                RaisePropertyChanged("CurrentObject");
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public void RaisePropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

Property:

private FormViewModel _viewModel;
public FormViewModel ViewModel
{ 
    get
    {
        if (_viewModel == null)
            _viewModel = new FormViewModel();

        return _viewModel;
    }
}

So now I’m trying to bind my data to TextBox like this:

TextBox.DataBindings.Add("Text", ViewModel, "CurrentObject.TestPropertyString");

And surprisingly, it doesn’t work! Nothing changes, when I change CurrentObject, or change TestPropertyString property.

But it works great, when I use:

TextBox.DataBindings.Add("Text", ViewModel.CurrentObject, "TestPropertyString");

---

So my question is: Does data binding support nested properties?

Thank you for explanations!

Answer 1

The Databinding behavior was changed in .NET 4.0. Your code works on .NET 3.5. I found this issue posted at Microsoft Connect: .Net 4.0 simple binding issue

Here was the work-around that worked for me. Use a BindingSource as the data object:

BindingSource bs = new BindingSource(_viewModel, null);

//textBox1.DataBindings.Add("Text", _viewModel, "CurrentObject.TestPropertyString");
textBox1.DataBindings.Add("Text", bs, "CurrentObject.TestPropertyString");