public partial class Form1 : Form {
    public Form1() {
        InitializeComponent();
        propertyGrid1.SelectedObject = testObject;
    }

    private void button1_Click(object sender, EventArgs e) {
        MessageBox.Show(testObject.Bar.Number.ToString());
    }

    private Example testObject = new Example();
}

class Example {
    public int Foo { get; set; }
    public Widget Bar { get; set; }
    public Example() {
        Bar = new Widget();
    }
}