private void creerUnToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Cree_un_compte c = new Cree_un_compte();

            c.MdiParent = this;
            c.Show();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            Cree_un_compte c = new Cree_un_compte();

            c.Show();
        }