Unable to Insert Data into Membership table.

I am simply create a form that accept some user details and insert some details into membership table and rest of other table.
Membership.CreateUser(username,password,email)
Roles.AddUserToRole(username,"user");
this will insert the details into the aspnet_users table and user is not assigned to any role and no membership record insert. Please give me some ideas how to do this.
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