Problem with query string

I am using Query string for getting the Product Details From Default page and when iam trying to redirect from default page to products page,the loop is not breaking and it's going forever.In default page I created one function in that I am retreiving data from data base and passing it to label control. When I tried the same logic with hyperlink,its working fine.Can Any one suggest me what I am doing Wrong?

 

Thanks in advance 

 

 
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