How to display all role in a dropdownlist in gridview with other information from other table. And set role when edited.

I display all information from a table called User_Profile. On the last column, I want to display a dropdownlist with all aspnet_Roles.RoleName in it (How to bind it in?). When edit mode, role selected is updated. I don't know where does the "role" was stored to identify each user (mean which table, which column does the role stored to identify each user with different role).
Currently i trying to use LINQ, but there are no link between User_Profile and aspnet_Roles. So, I cannot <%#Eval("aspnet_Roles.RoleName")%> in the gridview
Any solution?


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