using System;
using System.Windows.Forms;

class OwnerForm: Form
{
	Label label;
	public OwnerForm()
	{
		label = new Label();
		label.Text =  "label" ;

		Button button = new Button();
		button.Text =  "Show" ;
		button.Click += new EventHandler(OnButtonClick);
		button.Top = label.Bottom;

		Controls.AddRange(new Control[] {label, button});
	}

	// set свойство изменяющее Label.Text
	public string LabelText
	{
		set
		{
			label.Text = value;
		}
	}
	
	//Создание модального окна
	void OnButtonClick(object sender, EventArgs e)
	{
		OwnedForm ownedForm = new OwnedForm();
		ownedForm.ShowDialog(this);
	}
	
	static void Main()
	{
		Application.Run(new OwnerForm());
	}
}


class OwnedForm: Form
{
	public OwnedForm()
	{
		Button button = new Button();
		button.Click += new EventHandler(OnButtonClick);
		button.Text =  "Change" ;
		button.Parent = this;
	}

	//обновление Label owner'a
	void OnButtonClick(object sender, EventArgs e)
	{
		((OwnerForm)Owner).LabelText =  "new value" ;
	}
}