C# Windows Forms : BindingSource PositionChanged event not firing?

Question

I've got a simple winform with a bindingSource using a List as Data. I'd like to take action whenever the binding sources position is changed. Reading up, it looks like the 'positionChanged' event is what I need. However, in my app I'm unable to get this event to fire.

There is a bindingNavigator to use the bindingSoure for navigation and (for debugging) a button that changes the current binding source position.

I've tried to simplify this as much as possible. My form code looks like this :

public partial class Form1 : Form
{
    protected List<int> data;

    public Form1()
    {
        InitializeComponent();
        data = new List<int>();
        data.Add(4);
        data.Add(23);
        data.Add(85);
        data.Add(32);
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        bindingSource1 = new BindingSource();
        bindingSource1.DataSource = data;
        bindingNavigator1.BindingSource = this.bindingSource1;            
    }

    private void bindingSource1_PositionChanged(object sender, EventArgs e)
    {
        // Debugger breakpoint here. 
        // Expectation is this code will be executed either when
        // button is clicked, or navigator is used to change positions. 
        int x = 0; 
    }

    private void button1_Click(object sender, EventArgs e)
    {
        bindingSource1.Position = 2;
    }
}

The eventHandler is autogenerated in the designer :

        // 
        // bindingSource1
        // 
        this.bindingSource1.PositionChanged += new System.EventHandler(this.bindingSource1_PositionChanged);

Now, the trouble is that whenever I run this, the 'PositionChanged' event just will not trigger. I've verified that bindingSource1.Position changes based on the navigator and the button. But no matter what I do, the event won't actually trip. I'm guessing this is something pretty stupid at this point, or I'm completely misinterpreting when the event is supposed to fire.

Using .NET 4.5

Answer 1

The problem is in your Form_Load

private void Form1_Load(object sender, EventArgs e)
{
    // this overrides the reference you have created in the desinger.cs file
    // either remove this line 
    bindingSource1 = new BindingSource(); 
    // or add this line  
    //  bindingSource1.PositionChanged += bindingSource1_PositionChanged;
    bindingSource1.DataSource = data;
    bindingNavigator1.BindingSource = this.bindingSource1;   
}

When you create the the new object new BindingSource(), it doesn't have the event PositionChanged subscribed. That is why you never hit your breakpoint.