IFieldResultFormatter interface

Implement this interface if you want to control how the field result is formatted.

public interface IFieldResultFormatter


Format(double, GeneralFormat)Called when Aspose.Words applies a number format switch, i.e. * Ordinal.
Format(string, GeneralFormat)Called when Aspose.Words applies a capitalization format switch, i.e. * Upper.
FormatDateTime(DateTime, string, CalendarType)Called when Aspose.Words applies a date/time format switch, i.e. @ “dd.MM.yyyy”.
FormatNumeric(double, string)Called when Aspose.Words applies a numeric format switch, i.e. # “#.##”.


Shows how to automatically apply a custom format to field results as the fields are updated.

public void FieldResultFormatting()
    Document doc = new Document();
    DocumentBuilder builder = new DocumentBuilder(doc);
    FieldResultFormatter formatter = new FieldResultFormatter("${0}", "Date: {0}", "Item # {0}:");
    doc.FieldOptions.ResultFormatter = formatter;

    // Our field result formatter applies a custom format to newly created fields of three types of formats.
    // Field result formatters apply new formatting to fields as they are updated,
    // which happens as soon as we create them using this InsertField method overload.
    // 1 -  Numeric:
    builder.InsertField(" = 2 + 3 \\# $###");

    Assert.AreEqual("$5", doc.Range.Fields[0].Result);
    Assert.AreEqual(1, formatter.CountFormatInvocations(FieldResultFormatter.FormatInvocationType.Numeric));

    // 2 -  Date/time:
    builder.InsertField("DATE \\@ \"d MMMM yyyy\"");

    Assert.IsTrue(doc.Range.Fields[1].Result.StartsWith("Date: "));
    Assert.AreEqual(1, formatter.CountFormatInvocations(FieldResultFormatter.FormatInvocationType.DateTime));

    // 3 -  General:
    builder.InsertField("QUOTE \"2\" \\* Ordinal");

    Assert.AreEqual("Item # 2:", doc.Range.Fields[2].Result);
    Assert.AreEqual(1, formatter.CountFormatInvocations(FieldResultFormatter.FormatInvocationType.General));


/// <summary>
/// When fields with formatting are updated, this formatter will override their formatting
/// with a custom format, while tracking every invocation.
/// </summary>
private class FieldResultFormatter : IFieldResultFormatter
    public FieldResultFormatter(string numberFormat, string dateFormat, string generalFormat)
        mNumberFormat = numberFormat;
        mDateFormat = dateFormat;
        mGeneralFormat = generalFormat;

    public string FormatNumeric(double value, string format)
        if (string.IsNullOrEmpty(mNumberFormat)) 
            return null;

        string newValue = String.Format(mNumberFormat, value);
        FormatInvocations.Add(new FormatInvocation(FormatInvocationType.Numeric, value, format, newValue));
        return newValue;

    public string FormatDateTime(DateTime value, string format, CalendarType calendarType)
        if (string.IsNullOrEmpty(mDateFormat))
            return null;

        string newValue = String.Format(mDateFormat, value);
        FormatInvocations.Add(new FormatInvocation(FormatInvocationType.DateTime, $"{value} ({calendarType})", format, newValue));
        return newValue;

    public string Format(string value, GeneralFormat format)
        return Format((object)value, format);

    public string Format(double value, GeneralFormat format)
        return Format((object)value, format);

    private string Format(object value, GeneralFormat format)
        if (string.IsNullOrEmpty(mGeneralFormat))
            return null;

        string newValue = String.Format(mGeneralFormat, value);
        FormatInvocations.Add(new FormatInvocation(FormatInvocationType.General, value, format.ToString(), newValue));
        return newValue;

    public int CountFormatInvocations(FormatInvocationType formatInvocationType)
        if (formatInvocationType == FormatInvocationType.All)
            return FormatInvocations.Count;

        return FormatInvocations.Count(f => f.FormatInvocationType == formatInvocationType);

    public void PrintFormatInvocations()
        foreach (FormatInvocation f in FormatInvocations)
            Console.WriteLine($"Invocation type:\t{f.FormatInvocationType}\n" +
                              $"\tOriginal value:\t\t{f.Value}\n" +
                              $"\tOriginal format:\t{f.OriginalFormat}\n" +
                              $"\tNew value:\t\t\t{f.NewValue}\n");

    private readonly string mNumberFormat;
    private readonly string mDateFormat;
    private readonly string mGeneralFormat; 
    private List<FormatInvocation> FormatInvocations { get; } = new List<FormatInvocation>();

    private class FormatInvocation
        public FormatInvocationType FormatInvocationType { get; }
        public object Value { get; }
        public string OriginalFormat { get; }
        public string NewValue { get; }

        public FormatInvocation(FormatInvocationType formatInvocationType, object value, string originalFormat, string newValue)
            Value = value;
            FormatInvocationType = formatInvocationType;
            OriginalFormat = originalFormat;
            NewValue = newValue;

    public enum FormatInvocationType
        Numeric, DateTime, General, All

See Also