C# XML Document , XPath Query

Select XML Nodes by Name

To find nodes in an XML file you can use XPath expressions. Method XmlNode.Selec­tNodes returns a list of nodes selected by the XPath string. Method XmlNode.Selec­tSingleNode finds the first node that matches the XPath string.
Suppose we have this XML file.

[XML]

<Names>
    <Name>
        <FirstName>John</FirstName>
        <LastName>Smith</LastName>
    </Name>
    <Name>
        <FirstName>James</FirstName>
        <LastName>White</LastName>
    </Name></Names>

To get all <Name> nodes use XPath expression /Names/Name. The first slash means that the <Names> node must be a root node. SelectNodes method returns collection XmlNodeList which will contain the <Name> nodes. To get value of sub node <FirstName> you can simply index XmlNode with the node name: xmlNode["FirstName"].InnerText. See the example below.

[C#]

XmlDocument xml = new XmlDocument();
xml.LoadXml(myXmlString); // suppose that myXmlString contains "<Names>...</Names>"XmlNodeList xnList = xml.SelectNodes("/Names/Name");
foreach (XmlNode xn in xnList)
{
  string firstName = xn["FirstName"].InnerText;
  string lastName = xn["LastName"].InnerText;
  Console.WriteLine("Name: {0} {1}", firstName, lastName);
}

The output is:

Name: John Smith
Name: James White

Select XML Nodes by Attribute Value

This example shows how to select nodes from XML document by attribute value. Use method XmlNode.Selec­tNodes to get list of nodes selected by the XPath expression. Suppose we have this XML file.

[XML]

<Names>
    <Name type="M">John</Name>
    <Name type="F">Susan</Name>
    <Name type="M">David</Name>
</Names>

To get all name nodes use XPath expression /Names/Name. To get only male names (to select all nodes with specific XML attribute) use XPath expression /Names/Name[@type='M'].

[C#]

XmlDocument xml = new XmlDocument();
xml.LoadXml(str);  // suppose that str string contains "<Names>...</Names>"XmlNodeList xnList = xml.SelectNodes("/Names/Name[@type='M']");
foreach (XmlNode xn in xnList)
{
  Console.WriteLine(xn.InnerText);
}

The output is:

John
David

Select Top XML Nodes using XPath

This example shows how to select Top N nodes of the specific name from an XML document. To select nodes from XML use method XmlNode.Selec­tNodes. Pass XPath expression as a parameter and the method returns a list of selected nodes. Suppose we have this XML file.

[XML]

<Names>
    <Name>James</Name>
    <Name>John</Name>
    <Name>Robert</Name>
    <Name>Michael</Name>
    <Name>William</Name>
    <Name>David</Name>
    <Name>Richard</Name>
</Names>

To get all <Name> nodes use XPath expression /Names/Name. If you don't want to selected all nodes, but only top 5 nodes, you can uses XPath expression like this /Names/Name[position() <= 5]. See the example below.

[C#]

XmlDocument xml = new XmlDocument();
xml.LoadXml(str);  // suppose that str string contains "<Names>...</Names>"XmlNodeList xnList = xml.SelectNodes("/Names/Name[position() <= 5]");
foreach (XmlNode xn in xnList)
{
  Console.WriteLine(xn.InnerText);
}

The output is:

James
John
Robert
Michael
William