How to replace merge field with HTML string using Mail merge

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

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

Dictionary<WParagraph, Dictionary<int, string>> paraToInsertHTML = new Dictionary<WParagraph, Dictionary<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 Dictionary(Of WParagraph, Dictionary(Of Integer, String)) = New Dictionary(Of WParagraph, Dictionary(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);  
            //Maintain HTML in collection.
            Dictionary<int, string> fieldValues = new Dictionary<int, string>();
            fieldValues.Add(mergeFieldIndex, args.FieldValue.ToString());
            //Maintain paragraph in collection.
            paraToInsertHTML.Add(paragraph, fieldValues);
            //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)
            'Maintain HTML in collection.
            Dim fieldValues As Dictionary(Of Integer, String) = New Dictionary(Of Integer, String)
            fieldValues.Add(mergeFieldIndex, args.FieldValue.ToString)
            'Maintain paragraph in collection.
            paraToInsertHTML.Add(paragraph, fieldValues)
            'Set field value as empty.
            args.Text = String.Empty
        End If
    End If
End Sub

Private void InsertHtml ()
{
    //Iterates through each item in the dictionary.
    foreach (KeyValuePair<WParagraph, Dictionary<int, string>> dictionaryItems in paraToInsertHTML)
    {
        WParagraph paragraph = dictionaryItems.Key as WParagraph;
        Dictionary<int, string> values = dictionaryItems.Value as Dictionary<int, string>;
        //Iterates through each value in the dictionary.
        foreach (KeyValuePair<int, string> valuePair in values)
        {
            int index = valuePair.Key;
            string fieldValue = valuePair.Value;
            //Inserts an HTML string at the same position of mergefield in a Word document.
            paragraph.OwnerTextBody.InsertXHTML(fieldValue, paragraph.OwnerTextBody.ChildEntities.IndexOf(paragraph), index);
        }
    }
    dictionaryObject.Clear();
}

Private Sub InsertHtml ()
    'Iterates through each item in the dictionary.
    For Each dictionaryItems As KeyValuePair(Of WParagraph, Dictionary(Of Integer, String)) In paraToInsertHTML
        Dim paragraph As WParagraph = CType(dictionaryItems.Key, WParagraph)
        Dim values As Dictionary(Of Integer, String) = CType(dictionaryItems.Value, Dictionary(Of Integer, String))
        'Iterates through each value in the dictionary.
        For Each valuePair As KeyValuePair(Of Integer, String) In values
            Dim index As Integer = valuePair.Key    
            Dim fieldValue As String = valuePair.Value
            'Inserts an HTML string at the same position of mergefield in a Word document.
            paragraph.OwnerTextBody.InsertXHTML(fieldValue, paragraph.OwnerTextBody.ChildEntities.IndexOf(paragraph), index)
        Next
    Next
    dictionaryObject.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 I'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 I'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