In this chapter, we have learned about the key features and fundamental elements of the Validation Application Block such as Validators, ValidatorFactory, ValidationResults, and Rule Sets. We have explored the various required and optional assemblies, the initial infrastructure configuration, and the individual feature-level configuration. We have also learned to validate objects using various approaches such as attributes, self-validation, programmatically, and through configuration. We have also seen how the Validation Application Block can be integrated with Windows Forms-based applications and ASP.NET web applications. Finally, we learned to implement a custom validator with a simple implementation of a US Zip Code Validator. In the next chapter, we will deep dive into the Security Application Block and learn to leverage Authorization Rule Provider and Security Cache Provider to authorize and cache security credentials.