Extracting custom attributes in an XSD file

I am able to get all the nodes using the System.Xml.Schema class, but I an not able to query the b:fieldInfo node and extract the attributes using any standard xml methods. I don't want to parse it as a string.

 <xs:complexType>
      <xs:sequence>
        <xs:element name="Line1">
          <xs:complexType>
            <xs:sequence>
              <xs:annotation>
                <xs:appinfo>
                  <groupInfo sequence_number="0"/>
                </xs:appinfo>
              </xs:annotation>
              <xs:element name="Start" type="xs:string">
                <xs:annotation>
                  <xs:appinfo>
                    <b:fieldInfo justification="left" pos_offset="0" pos_length="15" sequence_number="1" />