private void btn_alarm_Click(object sender, EventArgs e) { ButtonReset(); if (ActiveMdiChild != null) { if (this.ActiveMdiChild != mchildForm_Alarm) { //ActiveMdiChild.Close(); ActiveMdiChild.Hide(); } mchildForm_Alarm = ShowActiveForm(mchildForm_Alarm, typeof(alarm)) as alarm; mchildForm_Alarm.Show(); } else { mchildForm_Alarm = ShowActiveForm(mchildForm_Alarm, typeof(alarm)) as alarm; mchildForm_Alarm.Show(); } btn_alarm.BackColor = Color.Red; }