How to find controls in datalist

This code is datalist prerender event sample

Protected Sub showeventdetails_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles showeventdetails.PreRender

            If Not DotNetNuke.Security.PortalSecurity.IsInRoles(PortalSettings.AdministratorRoleName) Then
                For Each item As DataListItem In showeventdetails.Items
                    Dim c1 As ImageButton = DirectCast(item.FindControl("ImageButton1"), ImageButton)
                    c1.Visible = False
                Next
            End If
        End Sub