IValidationAttributeFormatter Interface
Definition
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Formats a validation error message template with attribute-specific arguments.
Used by the validation localization pipeline to produce fully formatted error messages
from localized templates that contain positional placeholders beyond {0} (the display name).
public interface class IValidationAttributeFormatterpublic interface IValidationAttributeFormattertype IValidationAttributeFormatter = interfacePublic Interface IValidationAttributeFormatterRemarks
To add formatting support for a custom validation attribute, you have two options:
- Implement IValidationAttributeFormatter directly on the attribute itself. ValidationAttributeFormatterRegistry checks for this first and uses the attribute as its own formatter automatically.
- Create a separate IValidationAttributeFormatter implementation and register it via AttributeFormatters by calling AddFormatter<TAttribute>(Func<TAttribute,IValidationAttributeFormatter>).
The following example shows how to register a formatter for a custom attribute:
public class MyAttributeFormatter(MyAttribute attribute) : IValidationAttributeFormatter
{
public string FormatErrorMessage(CultureInfo culture, string messageTemplate, string displayName)
=> string.Format(culture, messageTemplate, displayName, attribute.CustomProperty);
}
// Register it in Program.cs:
builder.Services.AddValidationLocalization(options =>
options.AttributeFormatters.AddFormatter<MyAttribute>(
attribute => new MyAttributeFormatter(attribute)));
Methods
| Name | Description |
|---|---|
| FormatErrorMessage(CultureInfo, String, String) |
Formats the specified |
