Invalid attempt to call metadata when reader is closed

Private Sub cmbstudentid_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbstudentid.SelectedIndexChanged
        Try
            Call connection()
            sqlstr = "select _Name,_course_enro from Admission__details where _Eno like '%" & cmbstudentid.SelectedItem & "'"
            cmd = New SqlCommand(sqlstr, con)
            dr = cmd.ExecuteReader
            While dr.Read
                Me.txtname.Text = dr(0)
                Me.txtcourseenrolled.Text = dr(1)
                sqlstr2 = "select Cfees from Course_details where Cname like '%" & txtcourseenrolled.Text & "'"
                Dim cmd2 = New SqlCommand(sqlstr2, con)
                If con.State = ConnectionState.Closed Then
                    con.Open()
                End If
                dr.Close()
' [error "Invalid attempt to call metadata when reader is closed" in next line -- SA]:
                dr1 = cmd2.ExecuteReader
                If dr1.HasRows = True Then
                    While dr1.Read
                       <big>Me.txtcoursefees.Text = dr(0)</big>
                    End While
                End If
                dr1.Close()
            End While
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
        con.Close()
    End Sub