How to do verification in XML with C#?

[Sean Len]

Hello, I currently working on a project where I need to insert a record into XML. I able to insert without problem. But I wonder how to varify do the same client name already exist? If yes, i want to ignore the insertion.

private void button3_Click(object sender, EventArgs e)
        {
            string FileName = ".\\MasterXml.xml";

            XmlTextReader reader = new XmlTextReader(FileName);
            XmlDocument doc = new XmlDocument();
            doc.Load(reader);
            reader.Close();
            XmlNode currNode;

            strFileName = ".//" + textBox1.Text + ".xml";
    
            XmlDocumentFragment docFrag = doc.CreateDocumentFragment();

            docFrag.InnerXml = "<Client>" + textBox1.Text + "</Client>" +
                "<XmlPath>" + strFileName.ToString() + "</XmlPath>";

            // insert the availability node into the document 
            currNode = doc.DocumentElement;
            currNode.InsertAfter(docFrag, currNode.LastChild);
            //save the output to a file 
            doc.Save(FileName);

            XmlTextWriter textWriter2 = new XmlTextWriter(strFileName.ToString(), null);
            textWriter2.WriteStartDocument();
            textWriter2.WriteStartElement("Report");
            textWriter2.WriteStartElement("Client");
            textWriter2.WriteValue(textBox1.Text);
            textWriter2.WriteEndElement();

            textWriter2.Close();
        }

[jkmyoung]

Find a Client node with the same client.

if (doc.SelectNode s("//Client[.=" + textBox1.Text + "]") == null){
insert (insert code) here
}