private void btn_Tear_Click(object sender, EventArgs e)
{
if (frmTear == null)
{
frmTear = new FormTear();
frmTear.Show();
//子窗口关闭后增加释放实例的功能
frmTear.FormClosing += ReleaseObjct_Tear;
}
else
{
//存在子窗口打开的时候，重新选择打开的子窗口
frmTear.Activate();
}
}
private void ReleaseObjct_Tear(object sender, FormClosingEventArgs e)
{
//释放实例
frmTear = null;
}
