Problem with opening & closing events in ContextMenuStrip

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C#

hi,i made a MenuStrip and ContextMenuStrip,in MenuStrip i have a exitToolStripMenuItem1 and i have button in my form,when i click on button exitToolStripMenuItem1 was show in Right click but my exitToolStripMenuItem1 hide from MenuStrip,how can i solve it with opening & closing events of ContextMenuStrip?

namespace Menu
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            ContextMenuStrip.Items.Add(exitToolStripMenuItem1);
        }

        private void ToolStripMenuItem1_Click(object sender, EventArgs e)
        {
            ToolStripMenuItem itmCurrent = (ToolStripMenuItem)sender;

            switch (itmCurrent.Name)
            {
                case "exitToolStripMenuItem1":

                    System.Windows.Forms.DialogResult interactionResult;
                    interactionResult = MessageBox.Show("Are you sure you want to exit?", "Exit", MessageBoxButtons.YesNo, MessageBoxIcon.Question, MessageBoxDefaultButton.Button2);

                    if (interactionResult == System.Windows.Forms.DialogResult.Yes)
                        Application.Exit();

                    break;
            }
        }
    }
}