How to update XML file in C#?

Question

the XML file that i have:

<NameList>
  <personDetail>
    <first_name>Rock</first_name>
    <last_name>Shajahan</last_name>
    <age>24</age>
  </personDetail>
</NameList>

In the main :

             XDocument doc = XDocument.Load(@"nameList.xml");

         var node = doc.Descendants("personDetail").FirstOrDefault(personDetail => personDetail.Element("first_name").Value == this.textBox1.Text);


         node.SetElementValue("first_name", this.textBox1.Text);
         node.SetElementValue("last_name", this.textBox2.Text);
         node.SetElementValue("age", this.textBox3.Text);

        Console.WriteLine(node);
        doc.Save(@"nameList.xml");

I don't have red id variable, when I update by node.SetElementValue("age", this.textBox3.Text); to change other variable (e.g. last_name) there are all works fine. But if i wanna change the "root" which "first_name", it will shows "An unhandled exception of type 'System.NullReferenceException' occurred".

Can you post the code that actually throws the exception? What does "I don't have red id variable" mean? As for your NullReferenceException, please refer to this: http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it — vesan, Nov 09 '15 at 05:14
Question is the last_name and age are successful. but the warning occurred when i wanna change the first_name. — HCOOLH, Nov 09 '15 at 05:22

score 1 · Accepted Answer · answered Nov 09 '15 at 05:29

//try this code

        string path = "path";
        var element = "first_name";
        var value = "Dev";

        try
        {
            string fileLoc = path;
            XmlDocument doc = new XmlDocument();
            doc.Load(fileLoc);
            XmlNode node = doc.SelectSingleNode("/NameList/personDetail/" + element);
            if (node != null)
            {
                node.InnerText = value;
            }
            else
            {
                XmlNode root = doc.DocumentElement;
                XmlElement elem;
                elem = doc.CreateElement(element);
                elem.InnerText = value;
                root.AppendChild(elem);
            }
            doc.Save(fileLoc);
            doc = null;
        }
        catch (Exception)
        {

        }

yes,It works, but still has a problem like( JOE C, 30) (Rock, B, 30) , wanna change JOE to Steven. If the age is same, It may shows (Steven C, 30) (Steven B, 30) ... Or use the method only for the root? — HCOOLH, Nov 09 '15 at 05:47
for query try XmlNode node = doc.SelectSingleNode("/NameList/personDetail/first_name[text()='JOE']"); and value = Steven — devnath, Nov 09 '15 at 06:32

How to update XML file in C#?

1 Answers1