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Mail Merge in Word Processing Document API

  • 10 minutes to read

This article shows how you can implement Mail Merge with Word Processing Document API. The example involves the following steps:

  1. Load a Document Template
  2. Add Mail Merge Fields to the Template
  3. Add a Data Source
  4. Merge Data into Template and Save Document

Load a Document Template

The template is a document that contains field placeholders. You will later replace these placeholders with actual fields that refer to data source columns.

Call the RichEditDocumentServer.LoadDocument or RichEditDocumentServer.LoadDocumentTemplate method to load a document template.

The code sample below loads the following template:


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

using (var wordProcessor = new RichEditDocumentServer())

Add Mail Merge Fields

The FieldCollection.Create method allows you to add fields to the template. Use one of the following fields to insert data from the database:

Inserts plain text.
Inserts formatted content: variables, document elements, or entire document content.

Inserts images. Use the INCLUDEPICTURE field as follows: {INCLUDEPICTURE "{PictureLocation}" \d} (the PictureLocation is the path to the desired picture).

Use the IUriStreamProvider service to insert pictures from a database.

The code sample below shows how to insert MERGEFIELD and INCLUDEPICTURE fields in the template. The first INCLUDEPICTURE field inserts an image from a database. (The "dbimg://" prefix is a stream generated by the IUriStreamProvider implementation). The second field inserts a static image from a file.


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

private static void AddMailMergeFields(Document document)
    DocumentRange[] pictureRanges = document.FindAll("Photo", SearchOptions.WholeWord);

    foreach (var pictureRange in pictureRanges)
        DocumentPosition picturePosition = pictureRange.End;

        // Delete the placeholder

        // Insert a field to a picture from a database
        Field pictureField = document.Fields.Create(picturePosition, @"INCLUDEPICTURE ""dbimg://{ placeholder }""");

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

        // Clear the placeholder range

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

    // Find a placeholder for another image
    // in the footer
    SubDocument footer = document.Sections[0].BeginUpdateFooter();
    DocumentRange[] imageRanges =
        footer.FindAll("image", SearchOptions.WholeWord);
    foreach (var imageRange in imageRanges)
        DocumentPosition imagePosition = imageRange.End;

        // Delete the phrase

        // Create a field at the placeholder's position
        footer.Fields.Create(imagePosition, @"INCLUDEPICTURE ""DevExpress-Logo-Large-Color.png""");

    // Find a placeholder for the FirstName field:
    DocumentRange[] nameRanges =
        document.FindAll("FirstName", SearchOptions.WholeWord);
    foreach (var nameRange in nameRanges)
        DocumentPosition namePosition = nameRange.End;

        // Delete the phrase

        // Create a field at the placeholder position
        document.Fields.Create(namePosition, @"MERGEFIELD ""FirstName""");

IUriStreamProvider Service Implementation

The code sample below shows the IUriStreamProvider implementation used to insert images from a database. The INCLUDEPICTURE field in the template has a nested MERGEFIELD that refers to the EmployeeID field from the database. The GetStream method parses the received URI (the INCLUDEPICTURE field) and finds the required data row, and returns the MemoryStream with an image.


Make sure that the MERGEFIELD field nested in the INCLUDEPICTURE field in the template refers to the data table’s primary key. Otherwise, the IUriStreamProvider service cannot correctly find the required table row.

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;

Use DOCVARIABLE Fields in the Mail Merge Template

The DOCVARIABLE field allows you to insert any type of content into a document – from a simple variable to dynamic data from a database or another document. Variables can be stored in a document or calculated within the RichEditDocumentServer.CalculateDocumentVariable event.

The code sample below demonstrates how to handle the event to calculate the DOCVARIABLE field value. In this example, this field should insert a number of years the employee worked at a company. The nested MERGEFIELD refers to the HireDate entry in the database.

private static void WordProcessor_CalculateDocumentVariable(object sender, CalculateDocumentVariableEventArgs e)
    if (e.Arguments.Count > 0)
        // Retrieve the MERGEFIELD field value
        DateTimeOffset hireDate = Convert.ToDateTime(e.Arguments[0].Value);
        DateTimeOffset currentDate = DateTime.Now;

        // Calculate the difference between the current date
        // and the hire date
        var dif = currentDate.Subtract(hireDate);

        // Calculate the number of years
        int years = dif.Days / 365;

        // Specify the DOCVARIABLE field value
        e.Value = years.ToString();
        e.Handled = true;
    e.Handled = true;

Add a Data Source

RichEditDocumentServer supports the following data source types:

  • System.Collections.IList
  • System.Collections.ArrayList
  • System.Data.DataTable

Use the RichEditMailMergeOptions.DataSource property to specify the data source used in a mail merge. If the data source contains multiple data tables, use the RichEditMailMergeOptions.DataMember property to define a specific data member.

The code sample below shows how to use the XML data source:

using DevExpress.XtraRichEdit;
using System.Data;

DataSet xmlDataSet = new DataSet();
xmlDataSet.Tables[0].PrimaryKey = new DataColumn[] {
     xmlDataSet.Tables[0].Columns[0] };

using (var wordProcessor = new RichEditDocumentServer())
    wordProcessor.Options.MailMerge.DataSource = xmlDataSet.Tables[0];

Merge Data into Template and Save the Document

Call the Document.MailMerge method to merge data into a template and save the document to the specified file or stream. You can use the MailMergeOptions class properties to specify additional mail merge options. Pass the MailMergeOptions object as the MailMerge method parameter to apply these options.


The control’s Options.MailMerge.DataSource property is ignored if you call the MailMerge method and pass a MailMergeOptions object as a parameter. Use the method parameter’s DataSource property to specify the data source instead.

The code sample below specifies mail merge options, runs the mail merge, and saves the document to the specified file.


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

using (var wordProcessor = new RichEditDocumentServer())
    wordProcessor.CalculateDocumentVariable += WordProcessor_CalculateDocumentVariable;

    // Register the URI provider service
    IUriStreamService uriStreamService = wordProcessor.GetService<IUriStreamService>();
    uriStreamService.RegisterProvider(new ImageStreamProvider(xmlDataSet.Tables[0], "Photo"));

    MailMergeOptions myMergeOptions =
    myMergeOptions.DataSource = xmlDataSet.Tables[0];
    myMergeOptions.MergeMode = MergeMode.NewSection;

    wordProcessor.MailMerge(myMergeOptions, "result.docx", DocumentFormat.OpenXml);

Mail Merge Events

RichEditDocumentServer ships with the following events to control specific mail merge steps:

Fires before mail merge starts.
Fires when mail merge is completed.
Fires before each data record is merged with the document in the mail merge process.
Fires after each data record is merged with the document in the mail merge process.

The code sample below shows how to handle the MailMergeRecordStarted and MailMergeRecordFinished events to insert additional content to the document:

View Example: Use DOCVARIABLE Fields

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

private static void srv_MailMergeRecordStarted(object sender, MailMergeRecordStartedEventArgs e)
    DocumentPosition position = e.RecordDocument.Range.Start;
    DocumentRange _range =
        e.RecordDocument.InsertText(position, String.Format("Created on {0:G}\n\n", DateTime.Now));
    CharacterProperties cp = e.RecordDocument.BeginUpdateCharacters(_range);
    cp.FontSize = 8;
    cp.ForeColor = Color.Red;
    cp.Hidden = true;

private static void srv_MailMergeRecordFinished(object sender, MailMergeRecordFinishedEventArgs e)
    e.RecordDocument.AppendDocumentContent("Docs\\bungalow.docx", DocumentFormat.OpenXml);


If your template document contains fields that are not bound to database fields, you can replace those fields with their values (unlink fields). Use the following methods to do this:

Use Reporting Components to Create Mail-Merge Documents

One more way to create mail-merge documents with better flexibility is to use Reporting Components: they support multiple data nesting levels, different data sources, and format data. Refer to the following article for details: Reporting - Use Embedded Fields (Mail Merge).

To use Reporting Components, select any of subscriptions that grants access to it: open the comparison table.

You can always download fully-functional 30-day trial version and try this functionality in your project:

Download: Free 30-Day Trial