C# ผมจะนำตัวแปร ที่ส่งค่าข้าง form มาแล้วนำไปใช้ยังไงครับ

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 WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.IsMdiContainer = true;
        }

        private void addToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Form2 frm = new Form2();
            frm.MdiParent = this;
            frm.Show();
        }

        private void closeToolStripMenuItem1_Click(object sender, EventArgs e)
        {
            this.ActiveMdiChild.Close();
        }

        private void saveToolStripMenuItem_Click(object sender, EventArgs e)
        {
            ((Form2)this.ActiveMdiChild).Save();
        }
    }
}