using System;
using System.Windows.Forms;
using System.IO;

class ex : Form
{
    TextBox tb1 = new TextBox();

    ex()
    {
        Text = "hello";
        tb1.Dock = DockStyle.Fill;
        tb1.Multiline = true;
        Controls.Add(tb1);

        MenuStrip ms = new MenuStrip();
        Controls.Add(ms);
        ToolStripMenuItem File = new ToolStripMenuItem("File");
        ms.Items.Add(File);

        ToolStripMenuItem mi = new ToolStripMenuItem("Open");
        mi.Click += new EventHandler(Open_Click);
        File.DropDownItems.Add(mi);
    }

    void Open_Click(object sender, EventArgs e)
    {
        tb1.Text = File.ReadAllText(@"C:\test\test1.txt");
    }

    static public void Main()
    {
        Application.Run(new ex());
    }
}