Formatting strings in rules

One of the available operations in Rules editor when building a function step is Format. The purpose of this operation is to convert a string or a series of strings to a custom format.

This operation functions similarly to the .NET composite formatting feature:

The (...) feature takes a list of objects and a composite format string as input. A composite format string consists of fixed text intermixed with indexed placeholders, called format items, that correspond to the objects in the list. The formatting operation yields a result string that consists of the original fixed text intermixed with the string representation of the objects in the list.(Microsoft documentation)

Additional related operations include:

• Format Text - Returns a formatted string that can contain references to entity fields using the dot notation - {entity.field:format} (Example)

• Format Single - Returns a formatted string with lookup target information. This operation uses two arguments. The first is a text with placeholders: {1} for entity ID, {2} for entity name. The second argument is a lookup field. More info  Webinar

Arguments

The Format operation in Rules editor has two arguments (parameters). The first argument describes how the second argument should be formatted.

• Arg1: Text = composite format string

• Arg2: StringList = format items

The first argument is composite format string(Microsoft documentation). Essentially, it says how the result should look, with placeholders for strings from the second argument.

• The placeholders are numbers in curly brackets that correspond to the index of a format item in argument 2.

• The first format item has the index {0}.

• The same format item can be used multiple times in a single composite format string.

• Each format item can be further customized. For example, you can return only a date portion of a datetime variable {0:d}, you can apply currency formatting to a number {0:C2}, and much more.

The second argument is a StringList type of variable, a series or array of strings (or format items).

Format examples

Form button that fills an email address

Add a button to your form. Add a Button Click rule that builds your email address from first name, last name, and a static suffix.

This is how it looks in the app:

More composite format string examples

Format Text example

In this example, add a button that concatenates multiple entity fields (with formatting) into a single sentence.

Rule

Here's the important part: "Format Text" in action.

The property {Entity.name}, first offered in {Entity.createdon:MMMM yyyy}, located in {Entity.address_city} ({Entity.address_country}) is available from {Entity.seller} for {Entity.price:C}.

Result in the app

See also

• Formatting strings in Report Designer

• https://docs.microsoft.com/en-us/dotnet/standard/base-types/composite-formatting

• https://docs.microsoft.com/en-us/dotnet/standard/base-types/custom-date-and-time-format-strings

• https://docs.microsoft.com/en-us/dotnet/standard/base-types/custom-numeric-format-strings

Last updated: July 23, 2026