private void frmMain_Load(object sender, EventArgs e)
        {
            this.IsMdiContainer = true;
        }

        private void tsbtnClose_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }

        private void toolStripButton1_Click(object sender, EventArgs e)
        {
            frmUser frmUser = new frmUser();
            frmUser.MdiParent = this;
            frmUser.Show();
        }