Domain Validator

Microsoft Enterprise Library 5.0

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Class Name: DomainValidator<T>

Attribute Name: DomainValidatorAttribute

Configuration tool name: Domain Validator


This validator checks that a value is one of the specified values in a specified set. For example, it can check that a name is "Tom," "Dick," "Harry," or "George" or that an integer is 2, 3, 5, 7, or 11. If the set only contains one value, you can use this validator to check for equality.


The following table lists the domain validator properties. The actual property names shown in the configuration tools are listed in the table description.




Domain - The set of values that specifies the acceptable elements. The value that you want to validate must be of the same type as the values in the list. The compiler checks this requirement if you directly invoke the validator in your code. If you use attributes, the application block throws an exception at run time if the type is incorrect. If you use configuration, the configuration tool displays an error if you enter an incorrect type. This value is required.


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.


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.


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 – The name to use for this validator.


Negated - This is a Boolean property. If it is set to True, it changes the validator's behavior so that it will fail if the condition is met instead of when it is not met. The default is False.


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


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 domain validator are listed in the following table.




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.


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.


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.


The following code example shows how to use the validator with attributes to ensure that a value is within a specified list of values.

C# Copy Code
public class Product
  [DomainValidator("each", "dozen", "gross")]
  public string SalesUnit
      return salesUnit;
  // ...
Visual Basic Copy Code
Public Class Product
  <DomainValidator("each", "dozen", "gross")> _
  ReadOnly Property SalesUnit(ByVal _salesUnit As String)
      Return _salesUnit
    End Get
  End Property
End Class