显示隐藏的子窗体失败！

Question

代码如下：        Form2 frm = null;
        private void button1_Click(object sender, EventArgs e)
        {
            frm = new Form2();
            frm.Owner = this;
            frm.Show();
        }        private void button2_Click(object sender, EventArgs e)
        {
            if (this.frm == null)
            {
                frm = new Form2();
                frm.Owner = this;
            }
            else
            {
                this.frm.Show();
                this.frm.TopMost = true;
                this.frm.Activate();
            }
            
        }点击button1新建Form2的一个实例然后把该窗体最小化，为什么点击button2的时候该隐藏的窗体不会显示出来呢？

Answer 1

private void button2_Click(object sender, EventArgs e)
        {
            if (this.frm == null)
            {
                frm = new Form2();
                frm.Owner = this;
            }
            else
            {                
                frm.WindowState = FormWindowState.Normal;
            }        }

Answer 2

        Form2 frm = null;
        private void button1_Click(object sender, EventArgs e)
        {
            frm = new Form2();
            frm.Owner = this;
            frm.StartPosition = FormStartPosition.CenterScreen;
            frm.WindowState = FormWindowState.Minimized;
            frm.Show();
        }        private void button2_Click(object sender, EventArgs e)
        {
            if (this.frm == null)
            {
                frm = new Form2();
                frm.Owner = this;
            }
            else
            {
                frm.WindowState = FormWindowState.Normal;
                this.frm.Show();
                this.frm.TopMost = true;
                this.frm.Activate();
            }
            
        }