> For the complete documentation index, see [llms.txt](https://docs.aurelia.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.aurelia.io/developer-guides/error-messages/4100-to-4106/aur4101.md).

# AUR4101

## Error Message

`AUR4101: No rule has been added`

## Description

This error occurs when attempting to use a validation rule provider that has no rules defined. This typically happens when:

1. Trying to validate an object before any validation rules have been configured
2. The rule provider was created but no rules were added to it
3. Rules were cleared or removed and validation is attempted on an empty rule set

## Common Scenarios

```typescript
// ❌ Problem: No rules defined
const ruleProvider = new ValidationRuleProvider();
// Attempting to validate without adding any rules
ruleProvider.validate(model); // Throws AUR4101
```

## Solution

```typescript
// ✅ Correct: Add rules before validation
import { ValidationRules } from '@aurelia/validation';

ValidationRules
  .ensure('userName').required().minLength(3)
  .ensure('email').required().email()
  .on(MyModel);

// Now validation will work
const result = await validator.validate(model);
```


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