如何从vb.net的数据读取器中读取组合框中的数据？

Question

以下内容是我的代码的一部分，但所有组合框均未显示任何结果。任何人都可以帮助解决此代码并允许在组合框中显示数据吗？

Using cmd4 = New SqlCommand(selectSql4, conn)
            cmd4.Parameters.AddWithValue("@fullname", txtFullname.Text)

            Using dr4 = cmd4.ExecuteReader

                If dr4.HasRows Then
                    btnEdit.Enabled = True
                    btnBrowse.Enabled = True

                    'read the data from the record 
                    dr4.Read()

                    cboSpoken1.Text = dr4("Spoken BM").ToString
                    cboWritten1.Text = dr4("Written BM").ToString
                    cboSpoken2.Text = dr4("Spoken ENG").ToString
                    cboWritten2.Text = dr4("Written ENG").ToString
                    cboSpoken3.Text = dr4("Spoken CHI").ToString
                    cboWritten3.Text = dr4("Written CHI").ToString