Simple databinding between textbox and form title

Question

I am new at C# and databinding, and as an experiment I was trying to bind the form title text to a property:

namespace BindTest
{
    public partial class Form1 : Form
    {
        public string TestProp { get { return textBox1.Text; } set { } }

        public Form1()
        {
            InitializeComponent();
            this.DataBindings.Add("Text", this, "TestProp");
        }
    }
}

Unfortunately, this does not work. I suspect it has something to do with the property not sending events, but I don't understand enough about databinding to know why exactly.

If I bind the title text directly to the textbox, like this:

this.DataBindings.Add("Text", textBox1, "Text")

Then it does work correctly.

Any explanation about why the first code sample does not work would be appreciated.

Answer 1

I think you need to implement the INotifyPropertyChanged Interface. You must implement this interface on business objects that are used in Windows Forms data binding. When implemented, the interface communicates to a bound control the property changes on a business object.

How to: Implement the INotifyPropertyChanged Interface

Answer 2

You must implement INotifyPropertyChanged interface. Try the following code and see what happens when you remove NotifyPropertyChanged("MyProperty"); from the setter:

private class MyControl : INotifyPropertyChanged
{
    private string _myProperty;
    public string MyProperty
    {
        get
        {
            return _myProperty;
        }
        set
        {
            if (_myProperty != value)
            {
                _myProperty = value;
                // try to remove this line
                NotifyPropertyChanged("MyProperty");
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged(string propertyName)
    {
        if(PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

private MyControl myControl;

public Form1()
{
    myControl = new MyControl();
    InitializeComponent();
    this.DataBindings.Add("Text", myControl, "MyProperty");
}

private void textBox1_TextChanged(object sender, EventArgs e)
{
    myControl.MyProperty = textBox1.Text; 
}