public variable. c#

namespace CodeSampleCS
{
    public partial class frmCS01 : Form
    {
        private string cnString = string.Empty;
        public frmCS01(string argument)
        {
            if (!string.IsNullOrEmpty(argument))
            {
                cnString = argument;
            }
            InitializeComponent();
        }

        private void frmCS01_Load(object sender, EventArgs e)
        {
            MessageBox.Show(string.Format("msg form{0}", !string.IsNullOrEmpty(cnString) ? string.Format(" - {0}", cnString) : "")); 
        }
    }
}
--------------------------------------------
namespace CodeSampleCS
{
    static class Program
    {
        public static string cnString = "";
        [STAThread]
        static void Main()
        {
            XmlTextReader xmlReader = new XmlTextReader("csNorthwind.xml");
            cnString = xmlReader.ReadElementString("connection");
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            MessageBox.Show("msg 1" + cnString);
            Application.Run(new frmCS01(cnString));
            MessageBox.Show("msg 2" + cnString);
        }
    }
}

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