using DevExpress.Office.Services;
using DevExpress.Xpf.RichEdit;
using DevExpress.XtraRichEdit.API.Native;

richEditControl.LoadDocument("template.docx");
//...

Imports DevExpress.Office.Services
Imports DevExpress.Xpf.RichEdit
Imports DevExpress.XtraRichEdit.API.Native

richEditControl.LoadDocument("template.docx")
'...

using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.API.Native;
//...

// Load the template into the RichEditControl instance.
richEditControl.LoadDocument(templatePath);

var regionInfo = richEditControl.Document.GetRegionHierarchy();

Console.WriteLine(String.Format($"Regions found: {regionInfo.Regions.Count}; " +
    $"\r\n Main region: {regionInfo.Regions[0].Name} " +
    $"\r\n Detail region: {regionInfo.Regions[0].Regions[0].Name}"));
Console.ReadKey();

Imports DevExpress.XtraRichEdit
Imports DevExpress.XtraRichEdit.API.Native
Imports System.IO

' Load the template into the word processor instance.
richEditControl.LoadDocument(templatePath)

Dim regionInfo = richEditControl.Document.GetRegionHierarchy()
Console.WriteLine(String.Format("Regions found: {0}; " &
                                vbCrLf & " Main region: {1} " &
                                vbCrLf & " Detail region: {2}",
                                regionInfo.Regions.Count,
                                regionInfo.Regions(0).Name,
                                regionInfo.Regions(0).Regions(0).Name))
Console.ReadKey()

using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.API.Native;
//...

// Build a path to the DOCX template file relative to the project's base directory.
var templatePath = Path.Combine(
    AppDomain.CurrentDomain.BaseDirectory,
    "data",
    "template.docx"
);

richEditControl.LoadDocument(templatePath);
GenerateMergeFields(richEditControl.Document);

void GenerateMergeFields(Document document)
{
    // Obtain the detail table (the second table in the document)
    Table detailTable = document.Tables[1];
    // Create the Quantity field
    document.Fields.Create(
        detailTable.Rows[2].Cells[1].Range.Start,
        "MERGEFIELD Quantity"
    );

    // Create the formula field to calculate Discount as a percentage
    Field discountField = document.Fields.Create(
        detailTable.Rows[2].Cells[3].Range.Start,
        "= { placeholder }*100 \\#0%"
    );

    // Find a placeholder for a nested MERGEFIELD
    DocumentRange nestedFieldRange = document.FindAll(
        "{ placeholder }",
        SearchOptions.WholeWord,
        discountField.CodeRange
    ).First();

    // Clear the placeholder range
    document.Delete(nestedFieldRange);

    // Create a nested DISCOUNT field
    document.Fields.Create(nestedFieldRange.Start, "MERGEFIELD Discount");
}
//...

Imports DevExpress.XtraRichEdit
Imports DevExpress.XtraRichEdit.API.Native
'...

' Build a path to the DOCX template file relative to the project's base directory.
Dim templatePath As String = Path.Combine( _
    AppDomain.CurrentDomain.BaseDirectory, _
    "data", _
    "template.docx" _
)

richEditControl.LoadDocument(templatePath)
GenerateMergeFields(richEditControl.Document)

Sub GenerateMergeFields(document As Document)
    ' Obtain the detail table (the second table in the document)
    Dim detailTable As Table = document.Tables(1)

    ' Create the Quantity field
    document.Fields.Create( _
        detailTable.Rows(2).Cells(1).Range.Start, _
        "MERGEFIELD Quantity" _
    )

    ' Create the formula field to calculate Discount as a percentage
    Dim discountField As Field = document.Fields.Create( _
        detailTable.Rows(2).Cells(3).Range.Start, _
        "= { placeholder }*100 \#0%" _
    )

    ' Find a placeholder for a nested MERGEFIELD
    Dim nestedFieldRange As DocumentRange = document.FindAll( _
        "{ placeholder }", _
        SearchOptions.WholeWord, _
        discountField.CodeRange _
    ).First()

    ' Clear the placeholder range
    document.Delete(nestedFieldRange)

    ' Create a nested DISCOUNT field
    document.Fields.Create(nestedFieldRange.Start, "MERGEFIELD Discount")
End Sub
'...

using System.Data;
using System.IO;
using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.API.Native;

// Subscribe to the CalculateDocumentVariable event
richEditControl.CalculateDocumentVariable += (sender, e) => 
    RichEditControl_CalculateDocumentVariable(sender, e, dataSet);

static void RichEditControl_CalculateDocumentVariable(
    object sender,
    CalculateDocumentVariableEventArgs e,
    DataSet dataSet
) {
    // Ensure arguments exist.
    if (e.Arguments.Count == 0)
        return;

    switch (e.VariableName) {
        // Process "Photo" DOCVARIABLE (embed inline image from Base64).
        case "Photo": {
            string id = e.Arguments[0].Value.ToString();
            // Exit the loop early if IDs are empty/invalid.
            if (id.Trim() == string.Empty || id.Contains("<")) {
                e.Value = " ";
                e.Handled = true;
                return;
            }

            // Look up the employee record and decode the image.
            DataTable employeesTable = dataSet.Tables[0];
            DataRow? row = employeesTable.Rows.Find(Convert.ToInt32(id));
            string? imageData = row?["Photo"] as string;

            if (imageData != null) {
                var imageProcessor = new RichEditDocumentServer();
                byte[] imageBytes = Convert.FromBase64String(imageData);

                Shape image = imageProcessor.Document.Shapes.InsertPicture(
                    imageProcessor.Document.Range.Start,
                    DocumentImageSource.FromStream(new MemoryStream(imageBytes))
                );
                image.TextWrapping = TextWrappingType.InLineWithText;

                // Set the RichEditDocumentServer with prepared content as the field value.
                e.Value = imageProcessor;
                e.Handled = true;
            } else {
                // No image found.
                e.Value = null;
            }
            break;
        }
    }
}

Imports System.Data
Imports System.IO
Imports DevExpress.XtraRichEdit
Imports DevExpress.XtraRichEdit.API.Native

' Subscribe to the CalculateDocumentVariable event
AddHandler richEditControl.CalculateDocumentVariable, Sub(sender, e) 
RichEditControl_CalculateDocumentVariable(sender, e, dataSet)

Private Shared Sub RichEditControl_CalculateDocumentVariable( _
    sender As Object, _
    e As CalculateDocumentVariableEventArgs, _
    dataSet As DataSet _
)
    ' Ensure arguments exist.
    If e.Arguments.Count = 0 Then Return

    Select Case e.VariableName
        ' Process "Photo" DOCVARIABLE (embed inline image from Base64).
        Case "Photo"
            Dim id As String = e.Arguments(0).Value.ToString()
            ' Exit the loop early if IDs are empty/invalid.
            If id.Trim() = String.Empty OrElse id.Contains("<") Then
                e.Value = " " : e.Handled = True : Return
            End If

            ' Look up the employee record and decode the image.
            Dim employeesTable As DataTable = dataSet.Tables(0)
            Dim row As DataRow = employeesTable.Rows.Find( _
                Convert.ToInt32(id) _
            )
            Dim imageData As String = If( _
                row Is Not Nothing, _
                TryCast(row("Photo"), String), _
                Nothing _
            )

            If imageData IsNot Nothing Then
                Dim imageProcessor As New RichEditDocumentServer()
                Dim imageBytes As Byte() = Convert.FromBase64String(imageData)

                Dim image As Shape = imageProcessor.Document.Shapes.InsertPicture( _
                    imageProcessor.Document.Range.Start, _
                    DocumentImageSource.FromStream(New MemoryStream(imageBytes)) _
                )
                image.TextWrapping = TextWrappingType.InLineWithText

                ' Set the RichEditDocumentServer with prepared content as the field value.
                e.Value = imageProcessor
                e.Handled = True
            Else
                ' No image found.
                e.Value = Nothing
            End If
    End Select
End Sub

using DevExpress.Office.Services;
using System;
using System.Data;
using System.IO;

public class ImageStreamProvider : IUriStreamProvider
{
    static readonly string prefix = "dbimg://";
    DataTable table;
    string columnName;

    public ImageStreamProvider(DataTable sourceTable, string imageColumn)
    {
        this.table = sourceTable;
        this.columnName = imageColumn;
    }

    public Stream GetStream(string uri)
    {
        // Parse the retrieved URI string
        uri = uri.Trim();
        if (!uri.StartsWith(prefix))
            return null;

        // Remove the prefix from the retrieved URI string
        string strId = uri.Substring(prefix.Length).Trim();
        int id;

        // Check if the string contains the primary key
        if (!int.TryParse(strId, out id))
            return null;

        // Retrieve the row that corresponds
        // with the key
        DataRow row = table.Rows.Find(id);
        if (row == null)
            return null;

        // Convert the image string from this row
        // to a byte array
        byte[] bytes = Convert.FromBase64String(row[columnName] as string) as byte[];
        if (bytes == null)
            return null;

        // Return the MemoryStream with an image
        MemoryStream memoryStream = new MemoryStream(bytes);
        return memoryStream;
    }
}

Imports DevExpress.Office.Services
Imports System
Imports System.Data
Imports System.IO

Public Class ImageStreamProvider
    Inherits IUriStreamProvider

    Shared ReadOnly prefix As String = "dbimg://"
    Private table As DataTable
    Private columnName As String

    Public Sub New(ByVal sourceTable As DataTable, ByVal imageColumn As String)
        Me.table = sourceTable
        Me.columnName = imageColumn
    End Sub

    Public Function GetStream(ByVal uri As String) As Stream
        uri = uri.Trim()
        If Not uri.StartsWith(prefix) Then Return Nothing
        Dim strId As String = uri.Substring(prefix.Length).Trim()
        Dim id As Integer
        If Not Integer.TryParse(strId, id) Then Return Nothing
        Dim row As DataRow = table.Rows.Find(id)
        If row Is Nothing Then Return Nothing
        Dim bytes As Byte() = TryCast(Convert.FromBase64String(TryCast(row(columnName), String)), Byte())
        If bytes Is Nothing Then Return Nothing
        Dim memoryStream As MemoryStream = New MemoryStream(bytes)
        Return memoryStream
    End Function
End Class

using DevExpress.Office.Services;
using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.API.Native;

//...
IUriStreamService uriStreamService = richEditControl.GetService<IUriStreamService>();
uriStreamService.RegisterProvider(new ImageStreamProvider(xmlDataSet.Tables[0], "Photo"));

Imports DevExpress.Office.Services
Imports DevExpress.XtraRichEdit
Imports DevExpress.XtraRichEdit.API.Native

' ...
' Obtain the IUriStreamService from the RichEditDocumentServer.
Dim uriStreamService As IUriStreamService = richEditControl.GetService(Of IUriStreamService)()

' Register the custom ImageStreamProvider.
uriStreamService.RegisterProvider(New ImageStreamProvider(xmlDataSet.Tables(0), "Photo"))

public class NWindData {
    public List<Customer> Customers { get; set; } = new();

    public record Customer(
        string CustomerId,
        string CompanyName,
        string ContactName,
        string Country,
        string Address,
        string City,
        string Phone,
        List<Order> Orders);

    public record Order(
        string OrderID,
        DateTime? OrderDate,
        string ShipCountry,
        double Freight,
        List<OrderDetails> OrderDetails);

    public record OrderDetails(
        int ProductId,
        string ProductName,
        int Quantity,
        decimal UnitPrice,
        double Discount);
}

Public Class NWindData
    Public Property Customers As List(Of Customer) = New List(Of Customer)()

    Public Class Customer
        Public Property CustomerId As String
        Public Property CompanyName As String
        Public Property ContactName As String
        Public Property Country As String
        Public Property Address As String
        Public Property City As String
        Public Property Phone As String
        Public Property Orders As List(Of [Order])

        Public Sub New(customerId As String, companyName As String, contactName As String, country As String, address As String, city As String, phone As String, orders As List(Of [Order]))
            Me.CustomerId = customerId
            Me.CompanyName = companyName
            Me.ContactName = contactName
            Me.Country = country
            Me.Address = address
            Me.City = city
            Me.Phone = phone
            Me.Orders = orders
        End Sub
    End Class

    Public Class [Order]
        Public Property OrderID As String
        Public Property OrderDate As DateTime?
        Public Property ShipCountry As String
        Public Property Freight As Double
        Public Property OrderDetails As List(Of OrderDetails)

        Public Sub New(orderID As String, orderDate As DateTime?, shipCountry As String, freight As Double, orderDetails As List(Of OrderDetails))
            Me.OrderID = orderID
            Me.OrderDate = orderDate
            Me.ShipCountry = shipCountry
            Me.Freight = freight
            Me.OrderDetails = orderDetails
        End Sub
    End Class

    Public Class OrderDetails
        Public Property ProductId As Integer
        Public Property ProductName As String
        Public Property Quantity As Integer
        Public Property UnitPrice As Decimal
        Public Property Discount As Double

        Public Sub New(productId As Integer, productName As String, quantity As Integer, unitPrice As Decimal, discount As Double)
            Me.ProductId = productId
            Me.ProductName = productName
            Me.Quantity = quantity
            Me.UnitPrice = unitPrice
            Me.Discount = discount
        End Sub
    End Class
End Class

using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.API.Native;
using System.Text.Json;
using word_processor_master_detail_merge;

// Build a path to the JSON data file relative to the project's base directory.
string dataPath = Path.Combine(
    AppDomain.CurrentDomain.BaseDirectory,
    "nwind_data.json"
);

// Extract the entire JSON file contents into a string.
string json = File.ReadAllText(dataPath);

// Declare a nullable NWind instance to hold deserialized data.
NWindData? nwind;
try
{
    // Deserialize the JSON payload to an NWindData instance.
    nwind = JsonSerializer.Deserialize<NWindData>(json);
}
catch (Exception ex)
{
    // Log the exception (including type and message) and abort further processing.
    Console.Error.WriteLine($"Deserialization failed: {ex}");
    return;
}

// Build a path to the DOCX template file relative to the project's base directory.
var templatePath = Path.Combine(
    AppDomain.CurrentDomain.BaseDirectory,
    "template.docx"
);

// Load the template into the word processor instance.
richEditControl.LoadDocument(templatePath);

// Create mail merge options.
MailMergeOptions myMergeOptions = richEditControl.Document.CreateMailMergeOptions();

// Assign the data source (Customers collection).
// Null-propagation prevents exceptions if deserialization has failed.
myMergeOptions.DataSource = nwind?.Customers;

Imports DevExpress.XtraRichEdit
Imports DevExpress.XtraRichEdit.API.Native
Imports System.Text.Json
Imports word_processor_master_detail_merge
Imports System.IO

' Build a path to the JSON data file relative to the project's base directory.
Dim dataPath As String = Path.Combine( _
    AppDomain.CurrentDomain.BaseDirectory, _
    "nwind_data.json" _
)

' Extract the entire JSON file contents into a string.
Dim json As String = File.ReadAllText(dataPath)

' Declare a nullable NWind instance to hold deserialized data.
Dim nwind As NWindData = Nothing
Try
    ' Deserialize JSON to an NWind instance (System.Text.Json).
    ' If the JSON shape is invalid for NWind, a JsonException (or other exception) may be thrown.
    nwind = JsonSerializer.Deserialize(Of NWindData)(json)
Catch ex As Exception
    ' Log the exception (type + message) and abort processing.
    Console.Error.WriteLine($"Deserialization failed: {ex}")
    Return
End Try

' Build a path to the DOCX template file relative to the project's base directory.
Dim templatePath As String = Path.Combine( _
    AppDomain.CurrentDomain.BaseDirectory, _
    "template.docx" _
)

' Load the template into the word processor instance.
richEditControl.LoadDocument(templatePath)

' Create mail merge options.
Dim myMergeOptions As MailMergeOptions = richEditControl.Document.CreateMailMergeOptions()

' Assign data source (Customers collection).
' Null-propagation avoids exceptions if deserialization has failed.
myMergeOptions.DataSource = If(nwind?.Customers, Nothing)

using DevExpress.Office.Services;
using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.API.Native;
using System.Diagnostics;

// Build a path to the DOCX template file relative to the project's base directory.
var templatePath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "data", "template.docx");

// Load the template into the word processor instance.
richEditControl.LoadDocument(templatePath);

// Create mail merge options.
MailMergeOptions myMergeOptions = richEditControl.Document.CreateMailMergeOptions();

// Assign the data source (Customers collection).
myMergeOptions.DataSource = nwind?.Customers;

// Each merged record starts in a new section, preserving page setup and headers/footers per record.
myMergeOptions.MergeMode = MergeMode.NewSection;

var outputPath = Path.Combine(Environment.CurrentDirectory, "result.docx");
richEditControl.MailMerge(myMergeOptions, outputPath, DocumentFormat.OpenXml);

Imports DevExpress.Office.Services
Imports DevExpress.XtraRichEdit
Imports DevExpress.XtraRichEdit.API.Native
Imports System.Diagnostics
Imports System.IO

' Build a path to the DOCX template file relative to the project's base directory.
Dim templatePath As String = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "data", "template.docx")

' Load the template into the word processor instance.
richEditControl.LoadDocument(templatePath)

' Create mail merge options.
Dim myMergeOptions As MailMergeOptions = richEditControl.Document.CreateMailMergeOptions()
myMergeOptions.DataSource = xmlDataSet.Tables(0)

' Assign the data source (Customers collection). Null-propagation prevents exceptions if deserialization has failed.
myMergeOptions.DataSource = If(nwind?.Customers, Nothing)

' Each merged record starts in a new section, preserving page setup and headers/footers per record.
myMergeOptions.MergeMode = MergeMode.NewSection

Dim outputPath As String = Path.Combine(Environment.CurrentDirectory, "result.docx")
richEditControl.MailMerge(myMergeOptions, outputPath, DocumentFormat.OpenXml)

using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.API.Native;

// Build the absolute path to the mail merge template document (DOCX).
var templatePath = Path.Combine(
    AppDomain.CurrentDomain.BaseDirectory,
    "template.docx"
);

// Load the template into the word processor instance.
richEditControl.LoadDocument(templatePath);

// Create mail merge options.
MailMergeOptions myMergeOptions = richEditControl.Document.CreateMailMergeOptions();

// Assign the data source (Customers collection). Null-propagation prevents exceptions
// if deserialization has failed.
myMergeOptions.DataSource = nwind?.Customers;

// Declare a temporary RichEditDocumentServer.
var tempWordProcessor = new RichEditDocumentServer();

// Iterate through each customer record.
for (int i = 0; i <= nwind?.Customers.Count - 1; i++)
{
    // Restrict merge to a single record.
    myMergeOptions.FirstRecordIndex = i;
    myMergeOptions.LastRecordIndex = i;

    // Reset the temporary document before each merge.
    tempWordProcessor.CreateNewDocument();

    // Execute the mail merge for the current record.
    richEditControl.MailMerge(myMergeOptions, tempWordProcessor.Document);

    // Produce a unique output filename per record (result0.docx, result1.docx, etc.).
    var outputPath1 = Path.Combine(
        Environment.CurrentDirectory,
        string.Format("result{0}.docx", i)
    );

    // Save the merged document in Open XML (DOCX) format.
    tempWordProcessor.SaveDocument(outputPath1, DocumentFormat.OpenXml);
}

Imports DevExpress.XtraRichEdit
Imports DevExpress.XtraRichEdit.API.Native
Imports System.IO

' Build the absolute path to the mail merge template document (DOCX).
Dim templatePath As String = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "template.docx")

' Load the template into the word processor instance.
richEditControl.LoadDocument(templatePath)

' Create mail merge options.
Dim myMergeOptions As MailMergeOptions = richEditControl.Document.CreateMailMergeOptions()

' Assign the data source (Customers collection). Null-propagation prevents exceptions
' if deserialization has failed.
myMergeOptions.DataSource = If(nwind?.Customers, Nothing)

' Declare a temporary RichEditDocumentServer.
Dim tempWordProcessor As New RichEditDocumentServer()

' Iterate through each customer record.
For i As Integer = 0 To If(nwind?.Customers?.Count, -1)
    ' Restrict merge to a single record.
    myMergeOptions.FirstRecordIndex = i
    myMergeOptions.LastRecordIndex = i

    ' Reset the temporary document before each merge.
    tempWordProcessor.CreateNewDocument()

    ' Execute the mail merge for the current record.
    richEditControl.MailMerge(myMergeOptions, tempWordProcessor.Document)

    ' Produce a unique output filename per record (result0.docx, result1.docx, etc.).
    Dim outputPath1 As String = Path.Combine(Environment.CurrentDirectory, $"result{i}.docx")

    ' Save the merged document in Open XML (DOCX) format.
    tempWordProcessor.SaveDocument(outputPath1, DocumentFormat.OpenXml)
Next

using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.API.Native;

richEditControl.MailMergeRecordStarted += (sender, e) => RichEditControl_OnMailMergeRecordStarted(sender, e, nwind?.Customers);

void RichEditControl_OnMailMergeRecordStarted(
    object sender,
    MailMergeRecordStartedEventArgs e,
    List<Customer> dataSet) {
    // Ensure the record index maps to an existing customer.
    if (e.RecordIndex >= 0 && e.RecordIndex < dataSet.Count)
    {
        // Get the current customer for this merge record.
        var current = dataSet[e.RecordIndex]; 

        // Skip merging this record if the CustomerId is ANTON (case-insensitive).
        if (string.Equals(current.CustomerId, "ANTON", StringComparison.OrdinalIgnoreCase))
        {
            e.Cancel = true;
        }
    }
}

Imports DevExpress.XtraRichEdit
Imports DevExpress.XtraRichEdit.API.Native

AddHandler richEditControl.MailMergeRecordStarted, Sub(sender, e) RichEditControl_OnMailMergeRecordStarted(sender, e, If(nwind?.Customers, Nothing))

Private Sub RichEditControl_OnMailMergeRecordStarted(
    sender As Object,
    e As MailMergeRecordStartedEventArgs,
    dataSet As List(Of Customer))

    ' Ensure the record index maps to an existing customer.
    If e.RecordIndex >= 0 AndAlso e.RecordIndex < dataSet.Count Then
        ' Get the current customer for this merge record.
        Dim current = dataSet(e.RecordIndex)

        ' Skip merging this record if the CustomerId is ANTON (case-insensitive).
        If String.Equals(current.CustomerId, "ANTON", StringComparison.OrdinalIgnoreCase) Then
            e.Cancel = True
        End If
    End If
End Sub