Expression has been evaluated and has no value - string binding

[Nick Valeontis]

code:
---------------- ---------------- ---------------- --------------------------------
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namespace TestApp {
public partial class Form1 : Form {

private object s = "1";

public Form1() {
InitializeComponent();
Binding b = new Binding("Text", s, null, false,
DataSourceUpdateMode.OnPropertyChanged);
textBox2.DataBindings.Add(b);
}

private void Form1_FormClosing(object sender, FormClosingEventArgs e) {
MessageBox.Show(" s = "+ s);
}

private void button1_Click_1(object sender, EventArgs e) {
//textBox2.DataBindings["Text"].ReadValue();
textBox2.DataBindings["Text"].WriteValue();
}

}
}
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problem:

-> textBox2.DataBindings["Text"].ReadValue();

works okay, value "1" is copied to the textbox.

However, if I change the value of the textbox to "5" and then try
textBox2.DataBindings["Text"].WriteValue(); nothing happens. When exiting
the form, s is still "1".

Have I misunderstood something?