GridView设置页面大小下拉页脚

I have a grid view in an update panel. In the footer of the grid view, I have a drop down allowing the user to select the number of records per page. The first time the user selects a page size using the drop down, it works. After the that, the selected index changed event of the drop down only fires every other time. So, odd numbered selections of drop down, selected index changed fires, even numbered times, selected index changed does not fire, and drop down reverts to first option, and grid view loads with that number of records.I have a grid view in an update panel. In the f