public partial class Form1 : Form
    {
        private InputData InputForm = new InputData();
 
        public Form1()
        {
            InitializeComponent();            
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            InputForm.Show();
        }
    }

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
 
namespace daniweb.twoforms
{
  public partial class frmMain : Form
  {
    public frmMain()
    {
      InitializeComponent();
    }
 
    private void buttonGetValues_Click(object sender, EventArgs e)
    {
      StringBuilder sb = new StringBuilder();
      sb.AppendLine("Value1: " + frmSettings.Value1);
      sb.AppendLine("Value2: " + frmSettings.Value2);
      sb.AppendLine("Value3: " + frmSettings.Value3);
      MessageBox.Show(sb.ToString());
    }
 
    private void buttonShowForm_Click(object sender, EventArgs e)
    {
      frmSettings.ShowForm();
    }
  }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
 
namespace daniweb.twoforms
{
  public partial class frmSettings : Form
  {
    static frmSettings instance;
 
    static frmSettings()
    {
      instance = new frmSettings();
    }
 
    public static string Value1
    {
      get { return instance.textBox1.Text; }
      set { instance.textBox1.Text = value; }
    }
 
    public static string Value2
    {
      get { return instance.textBox2.Text; }
      set { instance.textBox2.Text = value; }
    }
 
    public static string Value3
    {
      get { return instance.textBox3.Text; }
      set { instance.textBox3.Text = value; }
    }
 
    public static void ShowForm()
    {
      if (instance.Visible)
        instance.BringToFront();
      else
        instance.Show();
    }
 
    public frmSettings()
    {
      InitializeComponent();
 
      //This smokes out a bug in code if you accidently create 2 instances
      if (instance != null)
        throw new InvalidOperationException("Only one instance allowed");
 
      this.textBox1.Text = "default val 1";
      this.textBox2.Text = "default val 2";
      this.textBox3.Text = "default val 3";
    }
 
    private void frmSettings_FormClosing(object sender, FormClosingEventArgs e)
    {
      e.Cancel = true;
      this.Hide();
    }
  }
}

if (TopMost == false)
            {
                 //Dis play the form to the top
                this.TopMost = true;
            }
            else
            {
                // Display the form the ceter.
                TopMost = false;
            }