FieldMergingCallback

MailMerge.FieldMergingCallback property

Occurs during mail merge when a mail merge field is encountered in the document.

public IFieldMergingCallback FieldMergingCallback { get; set; }

Examples

Shows how to insert images stored in a database BLOB field into a report.

public void ImageFromBlob()
{
    Document doc = new Document(MyDir + "Mail merge destination - Northwind employees.docx");

    doc.MailMerge.FieldMergingCallback = new HandleMergeImageFieldFromBlob();

    string connString = $"Provider=Microsoft.ACE.OLEDB.12.0;Data Source={DatabaseDir + "Northwind.accdb"};";
    string query = "SELECT FirstName, LastName, Title, Address, City, Region, Country, PhotoBLOB FROM Employees";

    using (OleDbConnection conn = new OleDbConnection(connString))
    {
        conn.Open();

        // Open the data reader, which needs to be in a mode that reads all records at once.
        OleDbCommand cmd = new OleDbCommand(query, conn);
        IDataReader dataReader = cmd.ExecuteReader();

        doc.MailMerge.ExecuteWithRegions(dataReader, "Employees");
    }

    doc.Save(ArtifactsDir + "MailMergeEvent.ImageFromBlob.docx");
}

private class HandleMergeImageFieldFromBlob : IFieldMergingCallback
{
    void IFieldMergingCallback.FieldMerging(FieldMergingArgs args)
    {
        // Do nothing.
    }

    /// <summary>
    /// This is called when a mail merge encounters a MERGEFIELD in the document with an "Image:" tag in its name.
    /// </summary>
    void IFieldMergingCallback.ImageFieldMerging(ImageFieldMergingArgs e)
    {
        MemoryStream imageStream = new MemoryStream((byte[])e.FieldValue);
        e.ImageStream = imageStream;
    }
}

Shows how to execute a mail merge with a custom callback that handles merge data in the form of HTML documents.

public void MergeHtml()
{
    Document doc = new Document();
    DocumentBuilder builder = new DocumentBuilder(doc);

    builder.InsertField(@"MERGEFIELD  html_Title  \b Content");
    builder.InsertField(@"MERGEFIELD  html_Body  \b Content");

    object[] mergeData =
    {
        "<html>" +
            "<h1>" +
                "<span style=\"color: #0000ff; font-family: Arial;\">Hello World!</span>" +
            "</h1>" +
        "</html>", 

        "<html>" +
            "<blockquote>" +
                "<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</p>" +
            "</blockquote>" +
        "</html>"
    };

    doc.MailMerge.FieldMergingCallback = new HandleMergeFieldInsertHtml();
    doc.MailMerge.Execute(new[] { "html_Title", "html_Body" }, mergeData);

    doc.Save(ArtifactsDir + "MailMergeEvent.MergeHtml.docx");
}

/// <summary>
/// If the mail merge encounters a MERGEFIELD whose name starts with the "html_" prefix,
/// this callback parses its merge data as HTML content and adds the result to the document location of the MERGEFIELD.
/// </summary>
private class HandleMergeFieldInsertHtml : IFieldMergingCallback
{
    /// <summary>
    /// Called when a mail merge merges data into a MERGEFIELD.
    /// </summary>
    void IFieldMergingCallback.FieldMerging(FieldMergingArgs args)
    {
        if (args.DocumentFieldName.StartsWith("html_") && args.Field.GetFieldCode().Contains("\\b"))
        {
            // Add parsed HTML data to the document's body.
            DocumentBuilder builder = new DocumentBuilder(args.Document);
            builder.MoveToMergeField(args.DocumentFieldName);
            builder.InsertHtml((string)args.FieldValue);

            // Since we have already inserted the merged content manually,
            // we will not need to respond to this event by returning content via the "Text" property. 
            args.Text = string.Empty;
        }
    }

    void IFieldMergingCallback.ImageFieldMerging(ImageFieldMergingArgs args)
    {
        // Do nothing.
    }
}

See Also

MailMerge.CleanupParagraphsWithPunctuationMarks MailMerge.MailMergeCallback