在ASP.NET中，使用UpdatePanel更新页面时遇到一个问题：当Timer触发时，只有Label的时间戳更新，而图片没有刷新。原因在于AJAX更新易受浏览器缓存影响。解决方法是在ImageUrl末尾添加当前时间戳防止缓存，同时调用Update()方法确保UpdatePanel更新。代码示例中展示了如何在Timer事件处理程序中更新ImageUrl并强制Panel刷新。
问题
I have the following UpdatePanel that gets an image from an ashx handler all of which works fine when the page is refreshed. However, when the timer fires, the label is refreshed with current time, but never the image.
ImageUrl="~/getImage.ashx?cam=1" Width="303px" BorderWidth="10px" />
ontick="UpdateTimer_Tick" />
The timer routine is:
protected void UpdateTimer_Tick(object sender, EventArgs e)
{
DateStampLabel.Text = DateTime.Now.ToString();
}
Why isn't the image refreshed?
回答1:
AJAX in general is really prone to browser caching. I normally add a DateTime.Now.Ticks to the URL. Also, your UpdateMode is Conditional, you have to call Update():
protected void UpdateTimer_Tick(object sender, EventArgs e)
{
DateStampLabel.Text = DateTime.Now.ToString();
Image1.ImageUrl += "&CacheBuster=" + DateTime.Now.Ticks.ToString();
TimedPanel.Update();
}
来源：https://stackoverflow.com/questions/7472131/why-doesnt-aspupdatepanel-refresh-an-image
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