C#

public class Form2 : System.Windows.Forms
{
// ...
  private From1 m_Form1 = null;
  public Form1 Form1
  {
     get {return this.m_Form1;}
     set {this.m_Form1 = value;}
  }

  public void SomeFunctionUsingComponentsOnForm1()
  {
      if (this.m_Form1 == null)
         throw new ArgumentException("Form1 is not assigned.");
      this.m_Form1.components();
  }
}

public class Form1 : System.Windows.Forms
{
 // ....
 public void ShowForm2()
 {
   Form2 form2 = new Form2();
   form2.Form1 = this;
   form2.Show();
 }
}

public class Form1 : System.Windows.Form
{
   private static Form1 m_GlobalInstance;
   public Form1()
   { 
     // set global instance
     m_GlobalInstance = this;
   }
 
  protected override void OnClosed(EventArgs e)
   {
     // invalidate global instance
      m_GlobalInstance = null;
      base.OnClosed (e);
  }

  // ....
   
   // property to access global instance
   public static Form1 GlobalInstance
   {
     return m_GlobalInstance;
   }

}

public class Form2 : System.Windows.Form
{
  // ....
  public void SomeFunctionUsingComponentsOnForm1()  
  {
      if (Form1.GlobalInstance == null)
         throw new ArgumentException("Form1 is not yet created.");
      Form1.GlobalInstance.components();  
   }
}

class Form2 : Form
{
   Form1 form1;

   public Form2(Form1 form1)
   {
      this.form1 = form1;
   }
}