label的text属性和pictureBox的Image怎么重赋值?
abel2.Text   =   " ";
pictureBox3.Image   =   null;
两个控件先为空,我想再赋值;
label2.Text   =   "你好！ ";
pictureBox3.Image   =   System.Drawing.Image.FromFile( "E:\\图片\\d567.GIF ");

------解决方案--------------------
private void timer1_Tick(object sender, System.EventArgs e)
{
label1.Text = "Now: "+System.DateTime.Now.ToString();
label1.Invalidate();
if (System.DateTime.Now.Hour == 17 && System.DateTime.Now.Minute == 17)
{

this.Show();
this.WindowState = FormWindowState.Normal;
label2.Text = "上课啦！新的一天开始了！ ";
pictureBox3.Image = System.Drawing.Image.FromFile( "E:\\图片\\实验用图片\\d2.GIF ");
PlaySound( "1.wav ",
0,
SND_FILENAME | SND_ASYNC);

}

else if (System.DateTime.Now.Hour == 17 && System.DateTime.Now.Minute == 19)
{

this.Show();
this.WindowState = FormWindowState.Normal;
label2.Text = "您辛苦啦！下课休息一下吧！ ";
pictureBox3.Image = System.Drawing.Image.FromFile( "E:\\图片\\实验用图片\\d1.GIF ");
PlaySound( "2.wav ",
0,
SND_FILENAME | SND_ASYNC);

}
else
{
label2.Text = " ";
pictureBox3.Image = null;
}
}


这样写，像你那样写直接进第二if，当然不会再进第三个if了
------解决方案--------------------
else if(System.DateTime.Now.Hour == 17 && System.DateTime.Now.Minute != 17)
{
label2.Text = " ";
pictureBox3.Image = null;
}

去掉