Our motto is that validation is not just about the front-end, and we mean it!

We believe that validation deserves more attention than it usually enjoys.

Valy is designed to follow the following software design principles:

• DBC - design my contract
• DRY - don't repeat yourself
• IOC - inversion of control

The DRY principle is upheld by defining your validation logic in an humanly readable XML format and generate the individual validators from there.

An example validation setup for a person might look like this:

<validators>
  <validator name="UserNameValidator" base_type="System.string">
    <validator ref="StringNullOrEmpty" />
    <validator ref="Regex">
      <regex>^([a-zA-Z0-9]{6,15})$</regex>
    </validator>
  </validator>
  <validator name="PasswordValidator" base_type="System.string">
     <validator ref="StringNullOrEmpty" />
      <validator ref="Regex">
        <regex>^\w*(?=\w*\d)(?=\w*[a-z])(?=\w*[A-Z])\w*$</regex>
      </validator>
  </validator>
</validators>

<object type="Foo.Person, Foo">
  <invariants>
    <member name="UserName" type="System.string">
      <validator ref="UserNameValidator" />
    </member>
    <member name="Password" type="System.string">
      <validator ref="PasswordValidator" />
    </member>
  </invariatns>
  <preconditions>
    <property name="UserName" direction="set">
      <validator ref="UserNameValidator" />
    </property>
    <method name="SetPassword">
      <parameter name="password">
        <validator ref="PasswordValidator" />
      </parameter>
    </method>
  </preconditions>
</object>

From this definition Valy will generate classes used to enforce the validation definitions.

namespace Foo
{
  public class Person
  {
    private string userName;
    private string password;
    private IPersonValidator validation;

    public Person(IValidator validation)
    {
      this.validation = validation.For<Person>;
    }

    public string UserName
    {
      get
      {
        return userName;
      }
      set
      {
        if(validation.validateUserName(value))
          userName = value;
      }
    }

    public void SetPassword(string password)
    {
      if(validation.PreconditionFor(o => o.SetPassword, password))
        password = password;
    }
  }
}

It is not the best example in the world but still the power of valy is shown.