Introducing the Validation Application Block. Agenda Enterprise Library 3.0 Introduction Validation Application Block Overview Applying, using and.

Introducing the Validation Application Block

Agenda

Enterprise Library 3.0 Introduction

Validation Application Block Overview

Applying, using and creating Validators

Validating Data

Summary

Enterprise Library 3.0: New Features At a Glance New application blocks

• Validation Application Block

• Policy Injection Application Block

Improvements to existing application blocks• Data Access Application

Block

• Logging Application Block

.NET Framework 3.0 integration• Logging, Exception

Handling and Validation Application Blocks

Configuration improvements

• Visual Studio-integrated configuration tool

• Environmental Overrides

• Manageable Configuration Source

Automation

• Application Block Software Factory

• Strong Naming Guidance Package

Enterprise Library 3.0 Application Blocks

CachingCaching

SecuritySecurity

Data Data AccessAccess LoggingLogging

ExceptionExceptionHandlingHandling

ConfigConfigHelpers Helpers & Design& Design

Instrumen-Instrumen-tationtation

ObjectObjectBuilderBuilder

CryptographyCryptography

CoreCore

Policy InjectionPolicy InjectionValidationValidation

Agenda

Enterprise Library 3.0 Introduction

Validation Application Block Overview

Applying, using and creating Validators

Validating Data

Summary

Why Validate?

Security

• Protect against script injection and other attacks

Correctness

• Ensure the system doesn’t process invalid data

• Enforce business rules

• Ensure user input is compatible with internal structures, data schemas and external systems

Responsiveness

• Flag invalid data before performing expensive processing tasks

Why a Validation Application Block?

Validation is a requirement in all non-trivial applications

.NET provides some validation capabilities, but these are tied to UI technologies such as ASP.NET

• Often results in the need to re-implement the same validation rules in different parts of an application

Many common validation scenarios require writing a lot of “plumbing” code

Validation Application Block: Goals Specify your validation rules once

• In configuration

• Using attributes

• Programmatically

Easily validate data from anywhere in your application• Programmatically

• Integrated into Windows Forms, ASP.NET or WCF

Composable validation logic• Built-in library of common primitive validation rules

• Combine validation rules on type members and using Boolean logic

• Apply multiple validation rule sets to the same types

Using the Validation Application Block

Create your business objects

Decorate them with validation rules

• Using attributes, configuration or custom code

Validate your data where required

• Using the Validation Application Block API

• Integrated into Windows Forms or ASP.NET UIs

• Integrated into WCF Service Interfaces

• Using the Policy Injection Application Block

Process or display validation results

• Using code or integrated into UIs

Agenda

Enterprise Library 3.0 Introduction

Validation Application Block Overview

Applying, using and creating Validators

Validating Data

Summary

Supplied Validation Rules

Validation Application Block includes the following rules:• Not Null (value must not be null)

• Contains Characters (e.g. does not contain any of /\?<>”:)

• Regular Expression (e.g. value is a valid e-mail address)

• Range (e.g. must be from 10-20 or 1/1/1950 to 12/31/1999)

• Relative DateTime (e.g. birth date is more than 18 years ago)

• String Length (e.g. string is at least 8 characters long)

• Domain (e.g. must be one of {John, Paul, George, Ringo})

• Enum Conversion (e.g. string can be converted to a value in the Color enum type)

• Type Conversion (e.g. string can be converted to a DateTime)

• Property Comparison (e.g. MaxDate > MinDate)

All validation rules can be negated • E.g String Length must not be between 5 and 10 characters

Composing Validation Rules

You can build complex validation rule sets by combining multiple primitive rules

• Combining rules with Boolean AND / OR logic

• Assigning different validators to different members of a type

• Specifying how nested objects or collections are to be validated

A single type may have multiple rule sets that can be used in different contexts

• For example, Valid for displaying or Valid for persisting

• For example, Valid Customer or Preferred Customer

Specifying Validation Rules Using Attributes Attributes allow you to specify validation rules directly

within the type being validated

Validation logic cannot be changed without recompiling

You must own the source code of the type

[StringLengthValidator(1, 50, Ruleset="RuleSetA", MessageTemplate="Last Name must be 1-50 characters")]public string LastName{ get { return lastName; } set { lastName = value; }}

[RegexValidator(@"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*", MessageTemplate="Invalid e-mail address", Ruleset="RuleSetA")]public string Email{ get { return email; } set { email = value; }}

[ObjectValidator("RuleSetA", Ruleset="RuleSetA")]public Address Address{ get { return address; } set { address = value; }}

[StringLengthValidator(1, 50, Ruleset="RuleSetA", MessageTemplate="Last Name must be 1-50 characters")]public string LastName{ get { return lastName; } set { lastName = value; }}

[RegexValidator(@"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*", MessageTemplate="Invalid e-mail address", Ruleset="RuleSetA")]public string Email{ get { return email; } set { email = value; }}

[ObjectValidator("RuleSetA", Ruleset="RuleSetA")]public Address Address{ get { return address; } set { address = value; }}

Specifying Validation Rules Using Configuration Validation rules are stored in XML and can be edited

with the Enterprise Library configuration tool Validation logic can be changed without recompiling You don’t need to own the source code of the type

Specifying Validation Rules Using Self Validation Sometimes validation rules are best

expressed with code specific to a custom class

Self Validation allows you to create special methods that represent a class’s validation logic

[HasSelfValidation] public class TemperatureRange{     private int min;    private int max;

// ...  

   [SelfValidation]      public void CheckTemperature(ValidationResults results)     { if (max < min) results.AddResult(new ValidationResult("Max less than min", this, null, null, null));    } }

[HasSelfValidation] public class TemperatureRange{     private int min;    private int max;

// ...  

   [SelfValidation]      public void CheckTemperature(ValidationResults results)     { if (max < min) results.AddResult(new ValidationResult("Max less than min", this, null, null, null));    } }

Message Templates Define what message will be returned when a

validation call fails All validators include a default message

template• e.g. “The value must match the regular expression

"{3}" with options "{4}".”

You can define your own message template for a validator instance• Using a literal string

• Using a resource type and name (for localization)

A message template may contain tokens {0} {1} etc, that are replaced with values at runtime• Representing validated value, key, tag and validator-

specific values

Writing your own Validators

To create your own reusable validators:

• Write a new class deriving from Validator<T>

Include desired properties and constructors

Override DoValidate and call LogValidationResult if validation fails

Override DefaultMessageTemplate

Apply the ConfigurationElementType attribute to the class, referring to typeof(CustomValidatorData) or your own strongly typed configuration class

• Write a new class deriving from ValidatorAttribute

Include desired properties and constructors

Override DoCreateValidator

The Application Block Software Factory makes this easier

Agenda

Enterprise Library 3.0 Introduction

Validation Application Block Overview

Applying, using and creating Validators

Validating Data

Summary

Validating Data Programmatically Regardless of how you specify rules, objects are

validated in the same way

If validation fails, you get a ValidationResults object, containing a list of ValidationResult objects

Each result includes a message, tag, references to the object and property being validated, and a reference to the original validator.

Validator<Customer> validator = ValidationFactory.CreateValidator<Customer>("Ruleset");ValidationResults results = validator.Validate(customer);if (!results.IsValid){{ foreach (ValidationResult result in results) { Console.WriteLine("Message={0}, Key={1}, "Tag={2}", result.Message, result.Key.ToString(), result.Tag == null ? "null" : "\"" + result.Tag.ToString() + "\""); }}}

Validator<Customer> validator = ValidationFactory.CreateValidator<Customer>("Ruleset");ValidationResults results = validator.Validate(customer);if (!results.IsValid){{ foreach (ValidationResult result in results) { Console.WriteLine("Message={0}, Key={1}, "Tag={2}", result.Message, result.Key.ToString(), result.Tag == null ? "null" : "\"" + result.Tag.ToString() + "\""); }}}

Integrating with WinForms, ASP.NET or WCF Supplied “Integration Adapters” make it

easier to validate data in UI layers and service boundaries

Reuses validation rules defined in attributes and configuration

• Does not tie the validation logic with the UI or service interface layers

Integrating with Windows Forms

Windows Forms integration adapter allows you to associate a control with the validation rules for a particular type and member

• Implemented via the ValidationProvider extender control

• Adds properties to UI controls for binding to a property of the class being validated

• Integrates with the ErrorProvider control to display validation failures alongside the control being validated

• Includes events for converting user input to the correct type for validation

Integrating with ASP.NET

ASP.NET integration adapter allows you to associate a control with the validation rules for a particular type and member

• Implemented via the PropertyProxyValidator control, which is an ASP.NET Validator

• Each PropertyProxyValidator refers to the type and property being validated, the rule set to use and the control containing the input

• Includes events for converting user input to the correct type for validation

Validation occurs server side (no Javascript support)

• But can be used with AJAX techniques

Integrating with WCF

WCF integration implemented as a WCF Behavior that validates data at the service interface layer

• Rules are defined within data contract types or using attributes on the service contract

• Validation occurs automatically when the service is called

• If validation fails, a ValidationFault is returned to the caller

Integrating with WCF: Example

[ServiceContract(Namespace = "http://TestService")][ValidationBehavior]internal interface ITestService{ [OperationContract] [FaultContract(typeof(ValidationFault))] AddCustomerResponse AddCustomer(AddCustomerRequest request);

[OperationContract(Name = "Lookup")] [FaultContract(typeof(ValidationFault))] void LookupById( [RangeValidator(5, RangeBoundaryType.Inclusive, 100, RangeBoundaryType.Exclusive)] int id, [NotNullValidator] [StringLengthValidator(4, RangeBoundaryType.Inclusive, 32, RangeBoundaryType.Inclusive)] string customerName );}

[ServiceContract(Namespace = "http://TestService")][ValidationBehavior]internal interface ITestService{ [OperationContract] [FaultContract(typeof(ValidationFault))] AddCustomerResponse AddCustomer(AddCustomerRequest request);

[OperationContract(Name = "Lookup")] [FaultContract(typeof(ValidationFault))] void LookupById( [RangeValidator(5, RangeBoundaryType.Inclusive, 100, RangeBoundaryType.Exclusive)] int id, [NotNullValidator] [StringLengthValidator(4, RangeBoundaryType.Inclusive, 32, RangeBoundaryType.Inclusive)] string customerName );}

Validating Parameters using thePolicy Injection Application Block The Validation Application Block can be used

along with the Policy Injection Application Block to automatically validate method parameters

Rules can be specified within parameter types (as attributes or configuration), or as attributes directly on the parameter definitions

Objects must be created or wrapped using the PolicyInjection class

Validation Handler can be applied using attribute- or configuration-based policies

If validation fails, an ArgumentValidationException (containing the ValidationResults) will be thrown to the caller

PIAB + VAB Examplepublic class BankAccount : MarshalByRefObject{ private decimal balance;

[ValidationCallHandler] public void Withdraw([RangeValidator(typeof(Decimal), "0.0", RangeBoundaryType.Exclusive, "1000.0", RangeBoundaryType.Inclusive, MessageTemplate="Withdrawal amount must be between zero and 1000.")] decimal withdrawAmount) { if (withdrawAmount > balance) { throw new ArithmeticException(); } balance -= withdrawAmount; }}

public class BankAccount : MarshalByRefObject{ private decimal balance;

[ValidationCallHandler] public void Withdraw([RangeValidator(typeof(Decimal), "0.0", RangeBoundaryType.Exclusive, "1000.0", RangeBoundaryType.Inclusive, MessageTemplate="Withdrawal amount must be between zero and 1000.")] decimal withdrawAmount) { if (withdrawAmount > balance) { throw new ArithmeticException(); } balance -= withdrawAmount; }}

BankAccount account = PolicyInjection.Create<BankAccount>();try{ account.Withdraw(2000);}catch (ArgumentValidationException ex){ // Do Something}

BankAccount account = PolicyInjection.Create<BankAccount>();try{ account.Withdraw(2000);}catch (ArgumentValidationException ex){ // Do Something}

Agenda

Enterprise Library 3.0 Introduction

Validation Application Block Overview

Applying, using and creating Validators

Validating Data

Summary

Summary

The Validation Application Block provides:

• A comprehensive library of primitive validation rules

• The ability to define validation rule sets by applying multiple rules to types using attributes or configuration

• A simple API for validating data and processing results

• Simple integration with Windows Forms, ASP.NET and WCF applications

• Parameter validation, with the help of the Policy Injection Application Block

Resources

Download Enterprise Library and related resources from:

• http://msdn.microsoft.com/practices

Join the Enterprise Library Community at:

• http://codeplex.com/entlib

Share community extensions at:

• http://codeplex.com/entlibcontrib

Read blogs from the Enterprise Library team at:

• http://msdn.microsoft.com/practices/Comm/EntLibBlogs