C#

// Form1
using System;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        private Form2 form2;
        public Form1()
        {
            InitializeComponent();
            form2 = new Form2();
            form2.Show();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (form2 != null)
                MessageBox.Show(form2.GD);
        }
    }
}

// Form2
using System;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            GD = textBox1.Text;
        }

        public string GD
        {
            get;
            set;
        }
    }
}

public string GD
{
get { return GD; } // this is calling this property and so goes round in circles
set { GD = value; } // same here
}

public string GD
{
get { return gd; } // now referencing your private field, assuming that you called it 'gd'
set { gd = value; } // same here
}

public void textBox1_TextChanged(object sender, EventArgs e)
{

GD = textBox1.Text;
gd = GD; // this line is not needed. When you say <code>GD = textBox1.Text</code>, the lines in the set part of GD
                          // (called the setter, guess what the get part is called) get executed; <code>gd = value</code>.
                          // The <code>value</code> is whatever is on the right of the = in <code>GD = textBox1.Text</code>

}
private string gd;
public string GD
{
get { return gd; }
set { gd = value; }
}

if (mMyDs.SaveInfo(ref curInfo,ref curList,"Add"))
{
    // do whatever you want if all is well
}
else
{
    // do whatever you want when it goes bad. e.g. throw an exception
}