Type Conversion Validator

Class Name: TypeConversionValidator

Attribute Name: TypeConversionValidatorAttribute

Configuration tool name: Type Conversion Validator

Description

This validator checks that a string can be converted to a specific type. For example, the validator can check that "6.32" can be converted to a Double type or that "2007-02-09" can be converted to a DateTime type.

Properties

The following table lists the type conversion 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.
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, rather than 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.
TargetType	Target Type - The type to which you want to convert the string. You can either enter the type or select it with the Type Selector – System.Object dialog box.
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 type conversion 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 full name of the type to which the validator will attempt to convert.

Example

The following example shows how to use the type conversion validator with attributes to check if the string DiscountString can be converted to type Double.

public class Product
{
  [TypeConversionValidator(typeof(double))]
  public string DiscountString
  {
    get
    {
      return discountString;
    }
  }
  // ...
}

'Usage
Public Class Product
  <TypeConversionValidator(GetType(Double))> _
  ReadOnly Property DiscountString(ByVal _discountString As String)
    Get
      Return _discountString
    End Get
  End Property
  ' ...
End Class