Steven Swafford: Overworked and Underpaid

How to edit an XML file that contains a namespace

I must admit using xpath to query and find a specific node in an XML file is not my strongest point and when a namespace was part of the XML file it threw me off even more. A huge thank you goes out to Adam Sills for pointing out my errors.

Take the following XML file that was generated using the June 2005 Patterns and Practices library:

<?xml version="1.0" encoding="utf-8"?>
<dataConfiguration>
  <xmlSerializerSection type="Microsoft.Practices.EnterpriseLibrary.Data.Configuration.DatabaseSettings, Microsoft.Practices.EnterpriseLibrary.Data , Version=1.1.0.0, Culture=neutral, PublicKeyToken=null">
    <enterpriseLibrary.databaseSettings xmlns:xsd="http://www.w3.org/2001/XMLSchema " xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" defaultInstance="SQL Server Instance" xmlns=" http://www.microsoft.com/practices/enterpriselibrary/08-31-2004/data">
      <databaseTypes>
        <databaseType name="Oracle" type="Microsoft.Practices.EnterpriseLibrary.Data.Oracle.OracleDatabase , Microsoft.Practices.EnterpriseLibrary.Data, Version=1.1.0.0, Culture=neutral, PublicKeyToken=null" />
        <databaseType name="SQL Server" type="Microsoft.Practices.EnterpriseLibrary.Data.Sql.SqlDatabase , Microsoft.Practices.EnterpriseLibrary.Data, Version=1.1.0.0, Culture=neutral, PublicKeyToken=null" />
      </databaseTypes>
      <instances>
        <instance name="Oracle Instance" type="Oracle" connectionString="Oracle Connection String" />
        <instance name="SQL Server Instance" type="SQL Server" connectionString="SQL Server Connection String" />
      </instances>
      <connectionStrings>
        <connectionString xsi:type="OracleConnectionStringData" name="Oracle Connection String">
          <parameters>
            <parameter name="Data Source" value="null" isSensitive="false" />
            <parameter name="Password" value="null" isSensitive="false" />
            <parameter name="User Id" value="null" isSensitive="false" />
            <parameter name="Host" value="null" isSensitive="false" />
          </parameters>
          <packages />
        </connectionString>
        <connectionString name="SQL Server Connection String">
          <parameters>
            <parameter name="database" value="null" isSensitive="false" />
            <parameter name="Integrated Security" value="True" isSensitive="false" />
            <parameter name="server" value="(local)" isSensitive="false" />
          </parameters>
        </connectionString>
      </connectionStrings>
    </enterpriseLibrary.databaseSettings>
  </xmlSerializerSection>
</dataConfiguration>

Now what if I wanted to edit the Data Source value of the connectionString node that has a value of "Oracle Connection String"? To be brief let us assume I have a command button on a web form. The following code is placed in the Click event procedure:

// Instantiate a XmlDocument Object
System.Xml.XmlDocument xmlDoc = new System.Xml.XmlDocument();
xmlDoc.Load(file); //file that is passed in

// Instantiate a XmlNameSpaceManager Object
XmlNamespaceManager xmlNsMgr = new XmlNamespaceManager(xmlDoc.NameTable);

// Add the namespace
xmlNsMgr.AddNamespace("x", "http://www.microsoft.com/practices/enterpriselibrary/08-31-2004/data ");

// Data Source XPath String
string _xpathDS = "//x:connectionStrings/x:connectionString[@name='Oracle Connection String']/x:parameters/x:parameter[@name='Data Source']";

// Instantiate a XmlNode Object
System.Xml.XmlNode node1 = xmlDoc.SelectSingleNode(_xpathDS, xmlNsMgr);
if (node1 != null)
{
 node1.Attributes["value"].Value= "oracledb";
}

xmlDoc.Save(file);

That is all there is to it. As long as node1 is not null then the value of the Data Source is set to oracledb.