gistfile1.cs

public interface IPresenter
{
    void Initialize();
    object UI { get; }
}

gistfile2.cs

public interface IMyPresenter : IPresenter
{
}

gistfile3.cs

public interface IMyPresenterCallbacks
{
    void OnSave();
    void OnMyTextChanged();
}

gistfile4.cs

public class MyPresenter : IMyPresenter, IMyPresenterCallbacks
{
    private IMyView _view;

    public MyPresenter(IMyView view)
    {
        _view = view;
    }

    public object UI
    {
        get { return _view; }
    }

    public void Initialize()
    {
        _view.Attach(this);
        _view.SaveButtonText = "Save";
        _view.SaveButtonEnabled = false;
    }

    public void OnSave()
    {
        // Save _view.MyText
    }

    public void OnMyTextChanged()
    {
        _view.SaveButtonEnabled = !string.IsNullOrEmpty(_view.MyText);
    }
}

gistfile5.cs

public interface IView<TCallbacks>
{
    void Attach(TCallbacks presenter);
}

gistfile6.cs

public interface IMyView : IView<IMyPresenterCallbacks>
{
    string MyText { get; set; }
    string SaveButtonText { get; set; }
    bool SaveButtonEnabled { get; set; }
}

gistfile7.cs

public class MyView : Form, IMyView
{
    private Button _saveButton;
    private TextBox _myTextBox;

    public void Attach(IMyPresenterCallbacks callback)
    {
        _saveButton.Click += (sender, e) => callback.OnSave();
        _myTextBox.TextChanged += (sender, e) => callback.OnMyTextChanged();
    }

    public string MyText
    {
        get { return _myTextBox.Text; }
        set { _myTextBox.Text = value; }
    }

    public string SaveButtonText
    {
        get { return _saveButton.Text; }
        set { _saveButton.Text = value; }
    }

    public bool SaveButtonEnabled
    {
        get { return _saveButton.Enabled; }
        set { _saveButton.Enabled = value; }
    }
}