Question : where parameters aspx .net page

I have an aspx page that is working, but when i try to add where parameter I get an error that the parameter "cid" is no defined. what is worng?

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         DefaultContainerName="eSafetyEntities" EntitySetName="Documents" EntityTypeFilter="Documents"
         Select="it.[DocID],  it.[DocName], it.[Description], it.[DateCreated]"
         Where="it.Categories.CategoryId = @cid">

         
               
         
     
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the page is passing cid like this and have tested the value which is working:
 .......doc.aspx?cid=1              

Answer : where parameters aspx .net page

The Name of the parameter needs to match the name in the query. So, in your case it should be "cid" rather than "id":