如何使用/不使用ASP.net C＃中的CodeBehind将DropDownList中的SelectedValue作为查询字符串传递给LinkButton＃

I've been fiddling with this issue for quite sometime now where I am not able to pass the value of a DropDownList to a Link Button. The Eval doesn't seem to work at all. Here's the code:I've been fiddling with this issue for quite so