NodeList

NodeList class

Represents a collection of nodes matching an XPath query executed using the SelectNodes method.

public class NodeList : IEnumerable<Node>

Properties

Name Description
Count { get; } Gets the number of nodes in the list.
Item { get; } Retrieves a node at the given index.

Methods

Name Description
GetEnumerator() Provides a simple “foreach” style iteration over the collection of nodes.
ToArray() Copies all nodes from the collection to a new array of nodes.

Remarks

NodeList is returned by SelectNodes and contains a collection of nodes matching the XPath query.

NodeList supports indexed access and iteration.

Treat the NodeList collection as a “snapshot” collection. NodeList starts as a “live” collection because the nodes are not actually retrieved when the XPath query is run. The nodes are only retrieved upon access and at this time the node and all nodes that precede it are cached forming a “snapshot” collection.

Examples

Shows how to find all hyperlinks in a Word document, and then change their URLs and display names.

using System;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using Aspose.Words;
using Aspose.Words.Fields;
using NUnit.Framework;

namespace ApiExamples
{
    public class ExReplaceHyperlinks : ApiExampleBase
    {
        public void Fields()
        {
            Document doc = new Document(MyDir + "Hyperlinks.docx");

            // Hyperlinks in a Word documents are fields. To begin looking for hyperlinks, we must first find all the fields.
            // Use the "SelectNodes" method to find all the fields in the document via an XPath.
            NodeList fieldStarts = doc.SelectNodes("//FieldStart");

            foreach (FieldStart fieldStart in fieldStarts.OfType<FieldStart>())
            {
                if (fieldStart.FieldType == FieldType.FieldHyperlink)
                {
                    Hyperlink hyperlink = new Hyperlink(fieldStart);

                    // Hyperlinks that link to bookmarks do not have URLs.
                    if (hyperlink.IsLocal)
                        continue;

                    // Give each URL hyperlink a new URL and name.
                    hyperlink.Target = NewUrl;
                    hyperlink.Name = NewName;
                }
            }

            doc.Save(ArtifactsDir + "ReplaceHyperlinks.Fields.docx");
        }

        private const string NewUrl = @"http://www.aspose.com";
        private const string NewName = "Aspose - The .NET & Java Component Publisher";
    }

    /// <summary>
    /// HYPERLINK fields contain and display hyperlinks in the document body. A field in Aspose.Words 
    /// consists of several nodes, and it might be difficult to work with all those nodes directly. 
    /// This implementation will work only if the hyperlink code and name each consist of only one Run node.
    ///
    /// The node structure for fields is as follows:
    /// 
    /// [FieldStart][Run - field code][FieldSeparator][Run - field result][FieldEnd]
    /// 
    /// Below are two example field codes of HYPERLINK fields:
    /// HYPERLINK "url"
    /// HYPERLINK \l "bookmark name"
    /// 
    /// A field's "Result" property contains text that the field displays in the document body to the user.
    /// </summary>
    internal class Hyperlink
    {
        internal Hyperlink(FieldStart fieldStart)
        {
            if (fieldStart == null)
                throw new ArgumentNullException("fieldStart");
            if (fieldStart.FieldType != FieldType.FieldHyperlink)
                throw new ArgumentException("Field start type must be FieldHyperlink.");

            mFieldStart = fieldStart;

            // Find the field separator node.
            mFieldSeparator = FindNextSibling(mFieldStart, NodeType.FieldSeparator);
            if (mFieldSeparator == null)
                throw new InvalidOperationException("Cannot find field separator.");

            // Normally, we can always find the field's end node, but the example document 
            // contains a paragraph break inside a hyperlink, which puts the field end 
            // in the next paragraph. It will be much more complicated to handle fields which span several 
            // paragraphs correctly. In this case allowing field end to be null is enough.
            mFieldEnd = FindNextSibling(mFieldSeparator, NodeType.FieldEnd);

            // Field code looks something like "HYPERLINK "http:\\www.myurl.com"", but it can consist of several runs.
            string fieldCode = GetTextSameParent(mFieldStart.NextSibling, mFieldSeparator);
            Match match = gRegex.Match(fieldCode.Trim());

            // The hyperlink is local if \l is present in the field code.
            mIsLocal = match.Groups[1].Length > 0; 
            mTarget = match.Groups[2].Value;
        }

        /// <summary>
        /// Gets or sets the display name of the hyperlink.
        /// </summary>
        internal string Name
        {
            get => GetTextSameParent(mFieldSeparator, mFieldEnd); 
            set
            {
                // Hyperlink display name is stored in the field result, which is a Run 
                // node between field separator and field end.
                Run fieldResult = (Run) mFieldSeparator.NextSibling;
                fieldResult.Text = value;

                // If the field result consists of more than one run, delete these runs.
                RemoveSameParent(fieldResult.NextSibling, mFieldEnd);
            }
        }

        /// <summary>
        /// Gets or sets the target URL or bookmark name of the hyperlink.
        /// </summary>
        internal string Target
        {
            get => mTarget;
            set
            {
                mTarget = value;
                UpdateFieldCode();
            }
        }

        /// <summary>
        /// True if the hyperlinks target is a bookmark inside the document. False if the hyperlink is a URL.
        /// </summary>
        internal bool IsLocal
        {
            get => mIsLocal; 
            set
            {
                mIsLocal = value;
                UpdateFieldCode();
            }
        }

        private void UpdateFieldCode()
        {
            // A field's field code is in a Run node between the field's start node and field separator.
            Run fieldCode = (Run) mFieldStart.NextSibling;
            fieldCode.Text = string.Format("HYPERLINK {0}\"{1}\"", ((mIsLocal) ? "\\l " : ""), mTarget);

            // If the field code consists of more than one run, delete these runs.
            RemoveSameParent(fieldCode.NextSibling, mFieldSeparator);
        }

        /// <summary>
        /// Goes through siblings starting from the start node until it finds a node of the specified type or null.
        /// </summary>
        private static Node FindNextSibling(Node startNode, NodeType nodeType)
        {
            for (Node node = startNode; node != null; node = node.NextSibling)
            {
                if (node.NodeType == nodeType)
                    return node;
            }

            return null;
        }

        /// <summary>
        /// Retrieves text from start up to but not including the end node.
        /// </summary>
        private static string GetTextSameParent(Node startNode, Node endNode)
        {
            if ((endNode != null) && (startNode.ParentNode != endNode.ParentNode))
                throw new ArgumentException("Start and end nodes are expected to have the same parent.");

            StringBuilder builder = new StringBuilder();
            for (Node child = startNode; !child.Equals(endNode); child = child.NextSibling)
                builder.Append(child.GetText());

            return builder.ToString();
        }

        /// <summary>
        /// Removes nodes from start up to but not including the end node.
        /// Assumes that the start and end nodes have the same parent.
        /// </summary>
        private static void RemoveSameParent(Node startNode, Node endNode)
        {
            if (endNode != null && startNode.ParentNode != endNode.ParentNode)
                throw new ArgumentException("Start and end nodes are expected to have the same parent.");

            Node curChild = startNode;
            while ((curChild != null) && (curChild != endNode))
            {
                Node nextChild = curChild.NextSibling;
                curChild.Remove();
                curChild = nextChild;
            }
        }

        private readonly Node mFieldStart;
        private readonly Node mFieldSeparator;
        private readonly Node mFieldEnd;
        private bool mIsLocal;
        private string mTarget;

        private static readonly Regex gRegex = new Regex(
            "\\S+" + // One or more non spaces HYPERLINK or other word in other languages.
            "\\s+" + // One or more spaces.
            "(?:\"\"\\s+)?" + // Non-capturing optional "" and one or more spaces.
            "(\\\\l\\s+)?" + // Optional \l flag followed by one or more spaces.
            "\"" + // One apostrophe.    
            "([^\"]+)" + // One or more characters, excluding the apostrophe (hyperlink target).
            "\"" // One closing apostrophe.
        );
    }
}

See Also