Basically I just want to check if the last element in the XML document I have is called

<element99>

or not, and if so, read its attributes. What would be the most efficient way to do so?

Is there a way not to load entire XML doc into memory?

CodePudding user response：

You could evaluate the XPath expression boolean(/*/*[last()]/self::element99) which returns true if the last element contained in the root element is named element99. The expression /*/*[last()]/self::element99/@* returns the attributes of that element.

CodePudding user response：

In XPath you could do (//*)[last()][self::element99]/@*

or you could do //element99[not(following::*)]/@* - but this isn't quite the same thing - it will match an element99 that has children, and depending what you mean by "last", an element with children is never the last element in the document.

CodePudding user response：

You can use System.Xml.XmlReader. In this approach the file will be read element-by-element and will not be loaded fully in the memory.

The following method checks if an <element99> exists, and if it is the last element.

bool CheckXml(string path)
{
    XmlReader xmlReader = XmlReader.Create(new StreamReader(path));

    if (!xmlReader.ReadToFollowing("element99"))
        return false;

    if (xmlReader.NodeType != XmlNodeType.Element)
        return false;

    xmlReader.Skip();

    while (!xmlReader.EOF)
    {
        if (xmlReader.NodeType != XmlNodeType.EndElement && xmlReader.NodeType != XmlNodeType.Whitespace)
        {
            return false;
        }
        xmlReader.Read();
    }

    return true;
}

Since XmlReader only provides forward-only access, you have to

1. Read and store attributes before checking if the element is the last one.
2. Read the stream again and store the required attributes.