讀取xml的節點？

Question

怎麽讀取xml節點的内容，我要修改所有doc_msg節點下的fg節點，怎麽寫代碼？
<NewDataSet xmlns="http://tempuri.org/doc_msg.xsd">
    <doc_msg>
        <AUTO_SEQ>1</AUTO_SEQ>
        <TITLE>aaa</TITLE>
        <CONTENT>bbbb</CONTENT>
        <CREATE_USER>[email protected]</CREATE_USER>
        <CREATE_TIME>2006-06-12T16:08:39.1400000+08:00</CREATE_TIME>
        <FG>1</FG>
    </doc_msg>
    <doc_msg>
        <AUTO_SEQ>2</AUTO_SEQ>
        <TITLE>aaa</TITLE>
        <CONTENT>bbbb</CONTENT>
        <CREATE_USER>[email protected]</CREATE_USER>
        <CREATE_TIME>2006-06-12T16:54:51.2330000+08:00</CREATE_TIME>
        <FG>1</FG>
    </doc_msg>
    <doc_msg>
        <AUTO_SEQ>3</AUTO_SEQ>
        <TITLE>aaa</TITLE>
        <CONTENT>bbbb</CONTENT>
        <CREATE_USER>[email protected]</CREATE_USER>
        <CREATE_TIME>2006-06-12T16:54:51.2330000+08:00</CREATE_TIME>
        <FG>1</FG>
    </doc_msg>
    <doc_msg>
        <AUTO_SEQ>4</AUTO_SEQ>
        <TITLE>aaa</TITLE>
        <CONTENT>bbbb</CONTENT>
        <CREATE_USER>[email protected]</CREATE_USER>
        <CREATE_TIME>2006-06-12T16:58:19.7630000+08:00</CREATE_TIME>
        <FG>1</FG>
    </doc_msg>
    <doc_msg>
        <AUTO_SEQ>5</AUTO_SEQ>
        <TITLE>aaa</TITLE>
        <CONTENT>bbbb</CONTENT>
        <CREATE_USER>[email protected]</CREATE_USER>
        <CREATE_TIME>2006-06-12T16:58:19.7630000+08:00</CREATE_TIME>
        <FG>1</FG>
    </doc_msg>
    <doc_msg>
        <AUTO_SEQ>6</AUTO_SEQ>
        <TITLE>aaa</TITLE>
        <CONTENT>bbbb</CONTENT>
        <CREATE_USER>[email protected]</CREATE_USER>
        <CREATE_TIME>2006-06-12T16:58:19.7630000+08:00</CREATE_TIME>
        <FG>1</FG>
    </doc_msg>
</NewDataSet>