C#

class Form1 : Form
{
  Button openForm2;
  TextBox customer;
  public Form1()
  {
    openForm2 = new Button();
    Controls.Add(openForm2);
    openForm2.Click += new EventHandler(openForm2_Click);
 
    customer = new TextBox();
    Controls.Add(customer);
 
    // ...
  }
  void openForm2_Click(object sender, EventArgs e)
  {
    using (Form2 form = new Form2(this))
      form.ShowDialog(this);
  }
  // This is an example of encapsulation. Don't expose too much
  // information; only that which is required.
  public string Customer
  {
    get { return customer.Text; }
    set { customer.Text = value; }
  }
}
class Form2 : Form
{
  Form1 parent;
  public Form2(Form1 form)
  {
    parent = form;
  }
  // When you click a button or something, set parent.Customer to
  // whatever string you require.
}

class Form1 : Form
{
  protected override void OnPaint(PaintEventArgs e)
  {
    base.OnPaint(e); // Make sure the base implementation has a chance
                     // to paint, unless you want to handle ALL
                     // painting. See the documentation for
                     // Control.SetStyle in that case.
 
    Rectangle rect = Bounds.Inflace(-5, -5); // Deflate by 5 pixels
                                             // all around.
 
    e.Graphics.DrawRectangle(Pens.Black, rect);
  }
}

using System;
using System.IO;

public class test
{
	[STAThread]
	public static void Main()
	{
		test t = new test();
		t.Write();
	}

	private void Write()
	{
		using(StreamWriter sw = new StreamWriter(@"C:\test.txt"))
		{
			sw.WriteLine("Hello Nick");
		}
	}
}

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