ASP.NET

protected void dlPhotos_ItemCommand(object source, DataListCommandEventArgs e)
    {
        if (e.CommandName == "Select")
        {
            Response.Write("<script>");
          Response.Write("window.open(Default3.aspx','_self','toolbar=0,location=0,menubar=0,resizable=0,width=400,height=320')");
            Response.Write("</script>");
        }
    }

imgbtn2.Click += new ImageClickEventHandler(imgbtn2_Click);
imgbtn2.Command += new CommandEventHandler(imgbtn2_Command);
imgbtn2.Unload += new EventHandler(imgbtn2_Unload);

Dim query = From mm In dataContext.Mail_Message
                        Group Join mmr In dataContext.Mail_MessageRecipient On mm.MailMessageId Equals mmr.MailMessageId Into mmrm = Group From mrm In mmrm.DefaultIfEmpty
                        Group Join u In dataContext.Application_User On mm.SenderId Equals u.UserId Into us = Group From ums In us.DefaultIfEmpty
                        Group Join sr In dataContext.Personnel_StaffRecord On ums.StaffRecordId Equals sr.StaffRecordId Into srm = Group From smrm In srm.DefaultIfEmpty
                        Group Join ma In dataContext.Mail_MessageAttachment On mm.MailMessageId Equals ma.MailMessageId Into mam = Group From mamm In mam.DefaultIfEmpty
                        Where mm.MailMessageId = messageId
                        Select mrm.MailMessageRecipientId, smrm.Surname, smrm.Firstname, smrm.Othername, mm.Date, mm.Subject, mm.MailContent

            If query IsNot Nothing Then
                Dim row = query(1)
                With result
                    .MailMessageId = row.MailMessageRecipientId
                    .Sender = CStr(IIf(row.Surname Is Nothing, "BISM Limited", String.Format("{0} {1} {2}", row.Surname, row.Firstname, row.Othername)))
                    .Subject = row.Subject
                    .Body = row.MailContent
                    .Dates = row.Date
                    .RecipientNames = GetMailRecipients(messageId)
                    .Attachments = GetMailAttachments(messageId)
                End With
                ReadMessage(row.MailMessageRecipientId)
            End If

This is the error I get:

LINQ to Entities does not recognize the method 'VB$AnonymousType_48`7[System.Int64,System.String,System.String,System.String,System.DateTime,System.String,System.String] ElementAtOrDefault[VB$AnonymousType_48`7](System.Linq.IQueryable`1[VB$AnonymousType_48`7[System.Int64,System.String,System.String,System.String,System.DateTime,System.String,System.String]], Int32)' method, and this method cannot be translated into a store expression.

What am I getting wrong here?