Not Null Validator
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Class Name: NotNullValidator
Attribute Name: NotNullValidatorAttribute
Configuration tool name: Not Null Validator
Description
This validator checks that the value is not null (C#) or Nothing (Visual Basic).
Properties
The following table lists the Not Null Validator properties.
Property |
Description |
---|---|
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 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. |
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 Not Null 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. |
Example
The following code example shows how to use the validator with attributes to ensure that a value is not null.
public class Product
{
[NotNullValidator]
public Company Manufacturer
{
get
{
return manufacturer;
}
}
// ...
}
'Usage
Public Class Product
<NotNullValidator()> _
ReadOnly Property Manufacturer(ByVal _manufacturer As Company)
Get
Return _manufacturer
End Get
End Property
' ...
End Class