How Character Ranges Work

1. Allowing Only Uppercase Letters

CharAllowed = 'AZ';

Result:

• Allowed: A to Z

• Rejected: lowercase letters, numbers, special characters

This is commonly used for:

• Codes
• Identifiers
• Abbreviations

2. Allowing Both Uppercase and Lowercase Letters

If CharAllowed is left blank, Business Central allows:

• Uppercase letters
• Lowercase letters
• Numbers
• Special characters (depending on field type)

There is no implicit validation unless the property is explicitly defined.

3. Multiple Character Ranges

You can specify multiple allowed ranges by entering them in pairs.

Example:

CharAllowed = 'admpzz';

This is interpreted as:

• a–d
• m–p
• z–z

Allowed characters:

• a, b, c, d
• m, n, o, p
• z

Rejected: All characters outside the defined ranges.

This approach is useful when you want tight control over allowed values without writing custom validation code.

4. Allowing a Single Character

To allow only one specific character, repeat it twice:

CharAllowed = 'XX';

This allows:

• Only X

Rejected: All characters except X.

This can be useful for:

• Flags
• Fixed format fields
• Controlled indicators

Where CharAllowed Is Validated

This is the most important part to understand.

Validation Occurs When:

• A user enters or edits a value on a page

• A value is entered manually into a table field via UI

Validation Does NOT Occur When:

• The field value is assigned through AL code

• The field is updated through AL code, including assignments using Rec.Validate()

• The field is populated during data migration or background processing

Example:

Page Extension:

When to Use CharAllowed

Recommended use cases:

• UI-level data hygiene

• Code fields

• Identifiers

• Reference numbers

• Preventing accidental invalid input

Not recommended as the only validation mechanism when:

• Data can be inserted via code

• Data integrity is business critical