Bindingsource在textbox控件更新后不会更新

private void textBox1_TextChanged(object sender, EventArgs e)
{
    bindingSource1.EndEdit();
}

textBox1.DataBindings.Add("Text", bindingSource1, "PropertyName", true, DataSourceUpdateMode.OnPropertyChanged);

public class MyClass : INotifyPropertyChanged
{
    private string propertyName;

    public string PropertyName
    {
        get { return propertyName; }
        set
        {
            propertyName = value;
            OnPropertyChanged("PropertyName");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

MyClass myObject = new MyClass();
bindingSource1.DataSource = myObject;
textBox1.DataBindings.Add("Text", bindingSource1, "PropertyName", true, DataSourceUpdateMode.OnPropertyChanged);