Search error in mysql with visual basic .net

Good day, Send me this error

  

executereader the connection property has not been initialized

the error sends it here%% of%

Private Sub btnAgregar_Click(sender As Object, e As EventArgs) Handles btnBuscar.Click
        If (validarCampos() = False) Then
            MsgBox("Campos vacios", MsgBoxStyle.Information, "Validacion")
        Else


            SQL = "SELECT * FROM usuario WHERE UsuCod='" & txtCodigo.Text & "'"
            rst = BaseDatos.leer_Registro(SQL)

            If rst.Read() Then
                txtNombre.Text = rst(1)
                txtApellido.Text = rst(2)
                cmbRol.SelectedIndex = rst(3)
                txtEmail.Text = rst(6)
            Else
                MsgBox("El usuario a consultar no existe", MsgBoxStyle.Information, "Validacion")

            End If
        End If

    End Sub

this is the function that reads me

Public Shared Function leer_Registro(ByVal sql As String) As OdbcDataReader
        Try
            orden = New OdbcCommand(sql, conexion)
            Return orden.ExecuteReader()
        Catch ex As Exception
            MsgBox(ex.Message)
            MessageBox.Show("Error al leer Registro en la Base de Datos", "Error",
            MessageBoxButtons.OK, MessageBoxIcon.Error)
            Return Nothing
        End Try
    End Function