Apply Custom Formatting to Fields

What is this page about?

This page outlines how to apply custom formatting to fields (like merge fields or document variables) in Aspose.Words.

Sometimes users need to apply custom formatting to fields. In this article, we will look at a couple of examples of how this can be done.

To learn more options, see the full list of properties for each field type in the corresponding class in the Fields namespace.

How to Apply Custom Formatting to Field Result

Aspose.Words provides API for custom formatting of field’s result. You can implement IFieldResultFormatter interface to control how the field result is formatted. You can apply numeric format switch, i.e. # “#.##”, date/time format switch, i.e. @ “dd.MM.yyyy”, and number format switch, i.e. * Ordinal.

The following code example shows how to apply custom formatting for the field result:

How to evaluate IF condition

If you want to evaluate IF condition after mail merge, you can use the EvaluateCondition method that immediately returns the result of the expression evaluation.

The following code example shows how to use this method:

How to Apply Custom Formatting to Time Field

By default Aspose.Words updates TIME field with current culture short time format. We figured out that there is a difference between Microsoft Word formatting and .NET/Windows formatting, and also between different .NET Framework versions. If you want to format the TIME field according to your requirement, you can achieve this by implementing IFieldUpdateCultureProvider interface.

The following code examples shows how to apply custom formatting to the TIME field:

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FAQ

1. Q: How can I apply a numeric format (e.g., two decimal places) to a merge field result?
   A: Implement the IFieldResultFormatter interface and, in the FormatResult method, apply a numeric format string such as "#.00" to the field value. Register the formatter with Document.FieldOptions.ResultFormatter before updating the fields.

2. Q: What is the easiest way to format a date field with a custom pattern like dd.MM.yyyy?
   A: Use a field result formatter and apply the date format switch (\@ "dd.MM.yyyy"). Inside FormatResult, check if the field type is FieldDate and return DateTime.Parse(value).ToString("dd.MM.yyyy").

3. Q: How do I evaluate an IF field condition programmatically after a mail‑merge operation?
   A: Call FieldIf.EvaluateCondition(string condition) which returns a bool indicating the result. This method does not require the field to be inserted into the document; you can pass the condition string directly.

4. Q: The TIME field shows a different format than I expect on my server. How can I control its output?
   A: Implement IFieldUpdateCultureProvider and return a CultureInfo that matches the desired time format. Assign your provider to Document.FieldOptions.UpdateCultureProvider before calling Field.Update().

5. Q: Can I combine multiple format switches (numeric, ordinal, date) for a single field?
   A: Yes. In your IFieldResultFormatter implementation you can inspect the field code for switches such as \#, \@, and \*. Apply each switch sequentially to the raw field value to produce the final formatted result.