Introduction
IFormattable Interface provides functionality to format the value of an object into a string representation. A simple example using a record demonstrates how to display different properties, along with formatting and calculations.
- "A" or "Age" => $"{BirthDay.GetAge()}" does a calculation
- "B" => $"{BirthDay:O}" does special date formatting
Usage
Output
Applies to
| Product | Versions |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10, 11 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
Summary
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Note that the content is intentionally short to make it easier to learn.
Top comments (1)
The example makes a good case for keeping display formats explicit. One useful guard is to have the default format throw FormatException for unsupported specifiers rather than silently falling back, then add unit tests for each named format. That prevents a typo in a report or export from producing plausible-looking but unintended output.