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Regular Expression Validator

Class Name: RegexValidator

Attribute Name: RegexValidatorAttribute

Configuration tool name: Regular Expression Validator

Description

This validator checks that the value matches the pattern specified by a regular expression.

Properties

The following table lists the regular expression validator properties. The actual property names displayed in the configuration tools are listed in the table description.

Property

Description

MessageTemplate

Message Template - This property is a string containing template tokens that the validator replaces with values as it validates the target. Typically, it describes the validation result.

MessageTemplateResourceName

Template Resource Name - If you do not want to use the MessageTemplate property to hard-code a message template (perhaps for internationalization), you can use a template stored in the application resources. You must also specify a MessageTemplateResourceType value. If you include both a MessageTemplate value and a MessageTemeplateResourceName value, the MessageTemplate value takes precedence.

MessageTemplateResourceType

Template Resource Type - The resource type for the template you want to use. If you specify a MessageTemplateResourceName value, you must specify this value.

Name

Name – The name to use for this validator.

Options

This property sets the option to use when validating a pattern. Possible values are None, IgnoreCase, Multiline, ExplicitCapture, Compiled, Singleline, ECMAScript, CultureInvariant, IgnorePatternWhiteSpace, and RightToLeft. The default is None.

Pattern

This property defines the regular expression. It is required. You can either enter the expression or use the Regular Expression Editor dialog box.

PatternResourceName

RegEx Resource Name - If you do not want to use the Pattern property to hard-code a regular expression (perhaps for internationalization), you can use a regular expression stored in the application resources. You must also specify a PatternResourceName value. If you include both a Pattern value and a PatternResourceName value, the Pattern value takes precedence.

PatternResourceType

RegEx Resource Type - The enumeration element type.

PatternResourceTypeName

RegEx Resource Type Name - The resource type for the pattern you want to use. If you specify a PatternResourceName value, you must specify this value.

RegularExpression

Regular Expression - The regular expression to use to validate the value.

Tag

This property is a user-supplied string. Typically, it is used to sort or categorize validation results.

TypeName

Type Name – The fully qualified name of the type configuration element. This property cannot be edited.

Message Template Tokens

If the message template contains tokens (for example, "{0}"), the validator will replace these tokens with values when the ValidationResult is created. The tokens supported by the regular expression validator are listed in the following table.

Token

Meaning

{0}

This token represents the value of the object that is being validated. Although it can be useful to show the original value as a part of the validation message, you must be careful to avoid injection attacks by escaping any characters that can be used to attack the system that conveys the message to the user.

{1}

This token represents the key of the object that is being validated. When the validator is attached to a member of a type such as a property or a field, the key is set to the member name. When the validator is attached to an object, the key is null and the token is replaced by an empty string.

{2}

This token represents the tag that is specified on the validator instance. If no tag is supplied, the token is replaced by an empty string.

{3}

The regular expression pattern configured for the validator instance.

{4}

The regular expression options configured for the validator instance.

Example

The following example shows how to use the regular expression validator with attributes to check that an e-mail address is formed according to the pattern given by the regular expression.

public class Person
{
  [RegexValidator(@"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*")]
  public string EmailAddress
  {
    get
    {
      return emailAddress;
    }
  }
  // ...
}
'Usage
Public Class Person
  <RegexValidator("\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*")> _
  ReadOnly Property EmailAddress(ByVal _emailAddress As String)
    Get
      Return _emailAddress
    End Get
  End Property
  ' ...
End Class