Table of Contents

Namespace Dmnk.LocalizedDataAnnotations

NuGet Version

Localized System.ComponentModel.DataAnnotations.

Why?

Regrettably, System.ComponentModel.DataAnnotations is no longer localized in modern .NET. This would not be so big of an issue if one could at least provide their own translations. However, the only official way of doing this is on every single attribute usage. Even more weird/annoying is that the messages have almost not changed for a long time, so MS could just ship the old translations with minimal effort, maybe as a nuget package.

Overview

This package provides two mechanisms to work around this issue:

  • IValidator and LocalizedValidator behave pretty much exactly like Validator, but they will be localized by default, using the old translations from .NET Framework with some slight custom adaptations (see below). You can also provide your own translations by implementing IDefaultValidationMessageProvider.
  • LocalizedValidatorReflectionHack.Hack() rewrites the ResourceManager on a private field of an internal class in System.ComponentModel.DataAnnotations to use the old translations. This should be reasonably reliable, since it has been a long time since the last change to that class and the package in general. Use at your own risk though.

All default subclasses of ValidationAttribute are supported. Your own custom subclasses should use their own FormatMessage implementation anyway, so this package does not affect them.

Currently, only English, German and French translations are included. Pull requests are welcome. You may use the method outlined below to acquire the old translations.

Usage

IValidator and LocalizedValidator

Be aware that this approach re-implements the internal logic of validator. There are a good amount of test-cases. Just be aware of that risk profile.

using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using Dmnk.LocalizedDataAnnotations;

IValidator validator = new LocalizedValidator();
var model = new MyModel { Name = "" };
ValidationContext context = new ValidationContext(model);
ICollection<ValidationResult> results = new List<ValidationResult>();
bool isValid = validator.TryValidateObject(model, context, results, validateAllProperties: true);

class MyModel
{
    [Required]
    public string Name { get; set; }
}

LocalizedValidatorReflectionHack.Hack()

Be aware that some attributes cache their error message. This means that you cannot reliably switch culture at runtime and expect correct localization.

using Dmnk.LocalizedDataAnnotations;

// somewhere early in e.g. Program.cs
LocalizedValidatorReflectionHack.Hack();

How were the old translations acquired?

This is more for documentation of what was done here - you don't have to do it.

The old translations can be found by downloading the .NET Framework language packs.

Then, the .exe has to be extracted with e.g. 7-Zip. Then, extract the x64-Windows10.0-KB4073126-x64.cab or similar. There should then be a system.componentmodel.dataannotations.resources.dll in a directory like msil_system.componentmod..notations.resources_31bf3856ad364e35_4.0.15552.17062_de-de_b21fc9c5dc6a4ca2.

Open that up in e.g. dotPeek. You should see the resx file now under Resources.

From there, just copy/paste the key/value pairs into whatever resx file you have set up.

Do note that these files contain a lot more translations than just the validation messages, e.g. for thrown exceptions. Despite not being necessary, the original keys are left unchanged, mostly to make them more easily identifiable/reproducable. This may also mean though that you might get some localized exceptions when using the reflection hack.

How exactly were the translations files in this repo created?

The initial English version was taken from the current System.ComponentModel.DataAnnotations in net10. Then, a German version was extracted using the method above. There were a few keys missing:

In netfx, but not in net10 (de in this example):

  • (internal exception): ArgumentIsNullOrWhiteSpace
  • (internal exception): AttributeStore_Type_Must_Be_Public
  • (internal exception): AttributeStore_Unknown_Method
  • (honestly, no idea): Common_NullOrEmpty
  • (internal exception): ValidationContextServiceContainer_ItemAlreadyExists
  • (internal exception): ValidationContextServiceContainer_Must_Be_Method

Most of these are for internal exceptions and not user-facing. The only exception is Common_NullOrEmpty, of which I am unsure where it was used.

In net10, but not in netfx (en in this example):

  • (user-facing): AllowedValuesAttribute_Invalid
  • (user-facing): Base64StringAttribute_Invalid
  • (user-facing): DeniedValuesAttribute_Invalid
  • (internal exception): LengthAttribute_InvalidMaxLength
  • (internal exception): LengthAttribute_InvalidMinLength
  • (internal exception): LengthAttribute_InvalidValueType
  • (user-facing): LengthAttribute_ValidationError
  • (user-facing): RangeAttribute_ValidationError_MaxExclusive
  • (user-facing): RangeAttribute_ValidationError_MinExclusive
  • (user-facing): RangeAttribute_ValidationError_MinExclusive_MaxExclusive

As is clear in the list above, a lot of these are very much user-facing keys. As a native german, I (dominiksta) decided to write my own German translations of these keys and use AI for the missing French keys (For the time being. This library will likely see some use at my workplace, at which point the French translations will be revisited).

For the non-user-facing keys I decided to simply use the English versions.

Classes

LocalizedValidator

A localized version of IValidator based on the messages provided by the passed IDefaultValidationMessageProvider.

If no message provider is passed, the default best-effort provider will be used, for which see the package documentation.

UnlocalizedBuiltinValidator

Implements IValidator by simply delegating to the "real" Validator.

Interfaces

IValidator

Mimics the API of Validator such that we can e.g. have a localized version.

Edit this page