# AUR4206

## Error Message

`AUR4206: Unable to parse binding expression: {{expression}}`

## Description

This error occurs when the validation controller cannot parse the binding expression used with validation. This typically happens with complex or malformed binding expressions.

## Common Scenarios

```html
<!-- ❌ Problem: Complex expressions that can't be parsed -->
<input value.bind="user[getField()] & validate">
<input value.bind="(complex ? expression : here) & validate">
```

## Solution

```html
<!-- ✅ Correct: Simple, parseable expressions -->
<input value.bind="user.name & validate">
<input value.bind="formData.email & validate">
```

```typescript
// ✅ Correct: Move complex logic to component
export class MyComponent {
  get currentField() {
    return this.user[this.getField()];
  }
  
  set currentField(value) {
    this.user[this.getField()] = value;
  }
}
```

```html
<!-- ✅ Correct: Use computed property -->
<input value.bind="currentField & validate">
```


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