how to check a node whether exist before item("name") under System.Xml.XmlNode?

Question

node.Item("SendingTime") will get error if not exist in xml file

if not knowing the structure or path in xml file of specific node

how to check whether exist

node = new System.Xml.XmlNode
node.Item("SendingTime")

Answer 1

Can you post a small but complete example allowing us to reproduce the problem and also show us the exact error message?

When I do

            XmlDocument doc = new XmlDocument();
            doc.LoadXml(@"<root>
  <foo>
    <bar>bar 1</bar>
  </foo>
  <foo/>
</root>");
            foreach (XmlNode foo in doc.SelectNodes("root/foo"))
            {
                XmlNode bar = foo["bar"];
                if (bar != null)
                {
                    Console.WriteLine("bar InnerText: {0}.", bar.InnerText);
                }
                else
                {
                    Console.WriteLine("No bar element found.");
                }
            }

then the output is

bar InnerText: bar 1.
No bar element found.

so I don't get any error.

The same sample in VB looks like

        Dim doc As New XmlDocument()
        doc.LoadXml("<root><foo><bar>bar 1</bar></foo><foo/></root>")
        For Each foo As XmlNode In doc.SelectNodes("root/foo")
            Dim bar As XmlNode = foo.Item("bar")
            If bar IsNot Nothing Then
                Console.WriteLine("bar InnerText is {0}.", bar.InnerText)
            Else
                Console.WriteLine("No bar element found.")
            End If
        Next

Again the attempt to access the bar child element itself does not cause any error, of course you have to check then whether you got an object or null (C#) respectively Nothing (VB).

---

MVP Data Platform Development My blog

Answer 2

as yesterday in debug mode watch list, tried node.item("name") return throw exception in F#

so haven't really use <> null in code

now this works.

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人工低的人教人工高的人, 這又是什麼世界