How to Replace Merge Field with HTML String in WinForms DocIO?

using Syncfusion.DocIO.DLS;
using System.Data;
using System.IO;

Imports System.IO
Imports Syncfusion.DocIO
Imports Syncfusion.DocIO.DLS

Dictionary<WParagraph, List<KeyValuePair<int, string>>> paraToInsertHTML = new Dictionary<WParagraph, List<KeyValuePair<int, string>>>();
// Opens the template document.
using (WordDocument document = new WordDocument(Path.GetFullPath("Template.docx")))
{
    // Creates the mail merge events handler to replace merge field with HTML.
    document.MailMerge.MergeField += new MergeFieldEventHandler(MergeFieldEvent);
    // Gets data to perform the mail merge.
    DataTable table = GetDataTable();
    // Performs the mail merge.
    document.MailMerge.Execute(table);
    // Append HTML to paragraph.
    InsertHtml();
    // Removes the mail merge events handler.
    document.MailMerge.MergeField -= new MergeFieldEventHandler(MergeFieldEvent);
    // Saves the Word document instance.
    document.Save(Path.GetFullPath("Result.docx"));
}

Dim paraToInsertHTML As New Dictionary(Of WParagraph, List(Of KeyValuePair(Of Integer, String)))()
'Opens the template document.
Using document As WordDocument = New WordDocument("Template.docx", FormatType.Docx)
    'Creates the mail merge events handler to replace merge field with HTML.
    AddHandler document.MailMerge.MergeField, AddressOf MergeFieldEvent
    'Gets data to perform the mail merge.
    Dim table As DataTable = GetDataTable()
    'Performs the mail merge.
    document.MailMerge.Execute(table)
    'Append HTML to paragraph.
    InsertHtml()
    'Removes the mail merge events handler.
    RemoveHandler document.MailMerge.MergeField, AddressOf MergeFieldEvent
    'Saves the WordDocument instance.
    document.Save("Result.docx", FormatType.Docx)
End Using

public static void MergeFieldEvent(object sender, MergeFieldEventArgs args)
{
    if (args.TableName.Equals("HTML"))
    {
        if (args.FieldName.Equals("ProductList"))
        {
            //Gets the current merge field owner paragraph.
            WParagraph paragraph = args.CurrentMergeField.OwnerParagraph;
            //Gets the current merge field index in the current paragraph.
            int mergeFieldIndex = paragraph.ChildEntities.IndexOf(args.CurrentMergeField);
            // Check if this paragraph already has an entry in the dictionary.
            // If not, create a new list to store field index and value pairs.
            if (!paraToInsertHTML.TryGetValue(paragraph, out var fields))
            {
                fields = new List<KeyValuePair<int, string>>();
                paraToInsertHTML[paragraph] = fields;
            }
            // Add the current merge field's index and its value to the list
            fields.Add(new KeyValuePair<int, string>(mergeFieldIndex, args.FieldValue.ToString()));
            //Set field value as empty.
            args.Text = string.Empty;
        }
    }
}

Public Sub MergeFieldEvent(ByVal sender As Object, ByVal args As MergeFieldEventArgs)
   
  If args.TableName.Equals("HTML") Then
        If args.FieldName.Equals("ProductList") Then
            'Gets the current merge field owner paragraph.
            Dim paragraph As WParagraph = args.CurrentMergeField.OwnerParagraph
            'Gets the current merge field index in the current paragraph.
            Dim mergeFieldIndex As Integer = paragraph.ChildEntities.IndexOf(args.CurrentMergeField)
            ' Check if this paragraph already has an entry in the dictionary.
            ' If not, create a new list to store field index and value pairs.
            Dim fields As List(Of KeyValuePair(Of Integer, String)) = Nothing
            If Not paraToInsertHTML.TryGetValue(paragraph, fields) Then
                fields = New List(Of KeyValuePair(Of Integer, String))()
                paraToInsertHTML(paragraph) = fields
            End If
            ' Add the current merge field's index and its value to the list.
            fields.Add(New KeyValuePair(Of Integer, String)(mergeFieldIndex, args.FieldValue.ToString()))
            'Set field value as empty.
            args.Text = String.Empty
        End If
    End If
End Sub

         private static void InsertHtml()
        {
            //Iterates through each item in the dictionary.
            foreach (KeyValuePair<WParagraph, List<KeyValuePair<int, string>>> dictionaryItems in paraToInsertHTML)
            {
                // Get the paragraph where HTML needs to be inserted.
                WParagraph paragraph = dictionaryItems.Key;
                // Get the list of (index, HTML string) pairs for this paragraph.
                List<KeyValuePair<int, string>> values = dictionaryItems.Value;
                // Iterate through the list in reverse order
                for (int i = values.Count - 1; i >= 0; i--)
                {
                    // Get the index of the merge field within the paragraph.
                    int index = values[i].Key;
                    // Get the HTML content to insert.
                    string fieldValue = values[i].Value;
                    // Get paragraph position.
                    int paragraphIndex = paragraph.OwnerTextBody.ChildEntities.IndexOf(paragraph);
                    //Inserts HTML string at the same position of mergefield in Word document.
                    paragraph.OwnerTextBody.InsertXHTML(fieldValue, paragraphIndex, index);
                }
             }
            paraToInsertHTML.Clear();
        }

Private Sub InsertHtml ()
   ' Iterate through each item in the dictionary.
    For Each dictionaryItems As KeyValuePair(Of WParagraph, List(Of KeyValuePair(Of Integer, String))) In paraToInsertHTML
        ' Get the paragraph where HTML needs to be inserted.
        Dim paragraph As WParagraph = dictionaryItems.Key
        ' Get the list of (index, HTML string) pairs for this paragraph.
        Dim values As List(Of KeyValuePair(Of Integer, String)) = dictionaryItems.Value
        ' Iterate through the list in reverse order.
        For i As Integer = values.Count - 1 To 0 Step -1
            ' Get the index of the merge field within the paragraph.
            Dim index As Integer = values(i).Key
            ' Get the HTML content to insert.
            Dim fieldValue As String = values(i).Value
            ' Get paragraph position.
            Dim paragraphIndex As Integer = paragraph.OwnerTextBody.ChildEntities.IndexOf(paragraph)
            ' Inserts HTML string at the same position of mergefield in Word document.
            paragraph.OwnerTextBody.InsertXHTML(fieldValue, paragraphIndex, index)
        Next
    Next
    ' Clear the dictionary after processing.
    paraToInsertHTML.Clear()
End Sub

private DataTable GetDataTable()
{
    DataTable dataTable = new DataTable("HTML");
    dataTable.Columns.Add("CustomerName");
    dataTable.Columns.Add("Address");
    dataTable.Columns.Add("Phone");
    dataTable.Columns.Add("ProductList");
    DataRow datarow = dataTable.NewRow();
    dataTable.Rows.Add(datarow);
    datarow["CustomerName"] = "Nancy Davolio";
    datarow["Address"] = "59 rue de l'Abbaye, Reims 51100, France";
    datarow["Phone"] = "1-888-936-8638";
    // Reads HTML string from the file.
    string htmlString = File.ReadAllText("File.html");
    datarow["ProductList"] = htmlString;
    return dataTable;
}

Public Function GetDataTable() As DataTable
    Dim dataTable As DataTable = New DataTable("HTML")
    dataTable.Columns.Add("CustomerName")
    dataTable.Columns.Add("Address")
    dataTable.Columns.Add("Phone")
    dataTable.Columns.Add("ProductList")
    Dim datarow As DataRow = dataTable.NewRow
    dataTable.Rows.Add(datarow)
    datarow("CustomerName") = "Nancy Davolio"
    datarow("Address") = "59 rue de l'Abbaye, Reims 51100, France"
    datarow("Phone") = "1-888-936-8638"
    'Reads HTML string from the file.
    Dim htmlString As String = File.ReadAllText("File.html")
    datarow("ProductList") = htmlString
    Return dataTable
End Function