The Validation Application Block in Enterprise Library 3.0 has Message Template Tokens and support for Resource Files to ease the burden of creating custom error messages. The following class uses a custom string length validation error message, called InvalidStringLengthMessage, in a Resource File, called Resource1.resx:
public class Tag
{
private int _tagId;
public int TagId
{
get { return _tagId; }
set { _tagId = value; }
}
private string _name;
[StringLengthValidator(1, 200,
MessageTemplateResourceName = "InvalidStringLengthMessage",
MessageTemplateResourceType = typeof(Resource1))]
public string Name
{
get { return _name; }
set { _name = value; }
}
private string _description;
[StringLengthValidator(1, 100,
MessageTemplateResourceName = "InvalidStringLengthMessage",
MessageTemplateResourceType = typeof(Resource1))]
public string Description
{
get { return _description; }
set { _description = value; }
}
}
The resource file, Resource1, looks as follows:
The InvalidStringLengthMessage Value includes Message Template Tokens that are specific to the StringLengthValidator:
- {0} - The value being validated.
- {1} - The Key of the value being validated.
- {2} - The Tag of the validator instance.
- {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.
The tokens provide the ability to provide a single format for all Invalid StringLengthValidator Error Messages as opposed to creating an error message for each property that has a StringLengthValidator.
Instead of the Name Property having the default error message of:
"The length of the value must fall within the range "1" (Inclusive) - "200" (Inclusive)."
The error message is now:
Invalid Name, 1 - 200 Characters.
The use of Message Template Tokens and Resource Files really improve the creation and maintenance of custom error messages.