How to get all XML nodes with the same name without knowing their level?

Question

I have a XML Example:

<Fruits>
    <Red_fruits>
        <Red_fruits></Red_fruits>
    </Red_fruits>
    <Yellow_fruits>
        <banana></banana>
    </Yellow_fruits>
    <Red_fruits>
        <Red_fruits></Red_fruits>
    </Red_fruits>
</Fruits>

I have 4 Red_fruits tags, 2 of them shares the same ParentNode (Fruits), I want to get those which have the same ParentNode.

But I just want those which have the same name (Red_fruits), which means Yellow_fruits tag isn't included.

This is the way I am doing right now using C# language:

XmlDocument doc = new XmlDocument();
string selectedTag = cmbX.text;

if (File.Exists(txtFile.text))
{
    try
    {
        //Load
        doc.Load(cmbFile.text);

        //Select Nodes
        XmlNodeList selectedNodeList = doc.SelectNodes(".//" + selectedTag);
    }
    Catch
    {
        MessageBox.show("Some error message here");
    } 
 }

This is returning me all red_fruits, not just the ones that belongs to Fruits.

I can't make XmlNodeList = doc.SelectNodes("/Fruits/Red_fruits") because I want to use this code to read random XML files, so I don't know the exact name that specific node will have, I just need to put all nodes with the same name and same level into a XmlNodeList using C# Language.

Is there a way of achieve this without using LINQ? How to do that?

Answer 1

If you're simply trying to find the "next" or "previous" iteration of a single node, you can do the following and then compare it to the name

XmlNode current = doc.SelectSingleNode("Fruits").SelectSingleNode("Red_fruits");

XmlNode previous = current.NextSibling;
XmlNode next = current.NextSibling;

and you can iterate until you find the proper sibling

while(next.Name != current.Name)
{
    next = next.NextSibling;
}

or you can even get your list by invoking the 'Parent' property

XmlNodeList list = current.ParentNode.SelectNodes(current.Name);

Answer 2

An understanding on the usage of Single Slash / and Double slash // can help here.

Let's see how / and // work in relation to the root node. When / is used at the beginning of a path:

/a

it will define an absolute path to node a relative to the root. As such, in this case, it will only find a nodes at the root of the XML tree.

When // is used at the beginning of a path:

//a

it will define a path to node a anywhere within the XML document. As such, in this case, it will find a nodes located at any depth within the XML tree.

These XPath expressions can also be used in the middle of an XPath value to define ancestor-descendant relationships. When / is used in the middle of a path:

/a/b

it will define a path to node b that is an immediate direct descendant (ie. a child) of node a.

When // used in the middle of a path:

/a//b

it will define a path to node b that is ANY descendant of node a.

Coming back to your question:

// using GetElementsByTagName() return all the Elements having name: Red_Fruits

XmlDocument doc = new XmlDocument();
XmlNodeList nodes= doc.GetElementsByTagName("Red_Fruits"); 

//Using SelectNodes() method

XmlNodelist nodes = doc.SelectNodes("//Fruits/Red_Fruits"); 

// This will select all elements that are children of the <Fruits> element.

In case <Fruits> is the root element use the Xpath: /Fruits/Red_Fruits. [ a single slash /]

Answer 3

Worst case scenario, you can cycle through the XMLNode items in selectedNodeList and check the ParentNode properties. If necessary you could go recursive on the ParentNode check and count the number of times it takes to get to the root node. This would give you the depth of a node. Or you could compare the ParentNode at each level to see if it is the parent you are interested in, if that parent is not the root.

    public void Test(){


        XmlDocument doc = new XmlDocument();
        string selectedTag = cmbX.text;

        if (File.Exists(txtFile.text))
        {
            try
            {
                //Load
                doc.Load(cmbFile.text);

                //Select Nodes
                XmlNodeList selectedNodeList = doc.SelectNodes(".//" + selectedTag);
                List<XmlNode> result = new List<XmlNode>();
                foreach(XmlNode node in selectedNodeList){
                    if(depth(node) == 2){
                        result.Add(node);
                    }
                }
                // result now has all the selected tags of depth 2
            }
            Catch
            {
                MessageBox.show("Some error message here");
            } 
        }

    }

    private int depth(XmlNode node) {
        int depth = 0;
        XmlNode parent = node.ParentNode;
        while(parent != null){
            parent = node.ParentNode;
            depth++;
        }
        return depth;
    }