使用WPF动画实现，点击“开始”按钮，价格标签的数字就开始自动翻滚，点击“停止”按钮，数字停止翻滚，生成一个随机价格。-WPF animation, click on the " start" button, the price tag figures began automatically rolling, click the " Stop" button, digital stop rolling, and generate a random price.