当Form2关闭时，控制权被传递回打开它的表格。 Form1负责从Form2中获取数据，处理Form2的实例，然后将数据传递给Form3。

When Form2 closes, control is passed back to the form that opened it. Form1 is responsible for grabbing the data from Form2, Disposing the instance of Form2, then passing the data to Form3.