String Length Validator

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Class Name: StringLengthValidator

Attribute Name: StringLengthValidatorAttribute

Configuration tool name: String Length Validator

Description

This validator checks that the length of the string is within the specified range. The range may include or exclude the endpoints by omitting the lower or upper bound.

Properties

The following table lists the String Length Validator properties.

Property	Description
LowerBound	This is the minimum length of the target string. It must be of type Integer. The compiler checks this requirement if you directly invoke the validator in your code.
LowerBoundType	This property determines how to evaluate the LowerBound value. Possible values for LowerBoundType are Ignore, Inclusive, and Exclusive. The Ignore value means that the validator ignores the LowerBound value. This is the default. The Inclusive value means that the validator allows values that are equal to the LowerBound value. The Exclusive value means that the validator does not allow values that are equal to the LowerBound value.
MessageTemplate	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	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 MessageTemplateResourceTypeName value. If you include both a MessageTemplate value and a MessageTemeplateResourceName value, the MessageTemplate value takes precedence.
MessageTemplateResourceTypeName	The resource type for the template you want to use. If you specify a MessageTemplateResourceName value, you must specify this value.
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.
UpperBound	This is the maximum length of the target string. It must be type Integer. The compiler checks this requirement if you directly invoke the validator in your code.
UpperBoundType	This property determines how to evaluate the UpperBound value. Possible values for UpperBoundType are Ignore, Inclusive, and Exclusive. The Ignore value means that the validator ignores the UpperBound value. This is the default. The Inclusive value means that the validator allows values that are equal to the UpperBound value. The Exclusive value means that the validator does not allow values that are equal to the UpperBound value.

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 String Length 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 lower bound configured for the validator instance.
{4}	The lower bound type (Inclusive, Exclusive, or Ignore) configured for the validator instance.
{5}	The upper bound configured for the validator instance.
{6}	The upper bound type (Inclusive, Exclusive or Ignore) configured for the validator instance.

Example

The following example shows how to use the validator with attributes to check that the product code is a string between 1 and 10 characters long.

public class Product
{
  [StringLengthValidator(1, 10)]
  public string ProductCode
  {
    get
    {
      return productCode;
    }
  }
  // ...
}

'Usage
Public Class Product
  <StringLengthValidator(1, 10)> _
  ReadOnly Property ProductCode(ByVal _productCode As String)
    Get
      Return _productCode
    End Get
  End Property
End Class