Conditional validation for MVC applications
Data annotations, introduced in MVC2 are a great way to manage validation for your view models.
However, time and time again, you come across the standard multi-step form development question – I need field A to be required only if field B is set. Built in annotations don’t support this out of the box, so I like to use a package called Foolproof Validation.
Foolproof makes conditional validation fairly easy. It has built-in client-side validation support, so the conditional validation will be performed both client and server side.
Take this example:
public bool Married { get; set; }
[RequiredIfTrue("Married")]
public string MaidenName { get; set; }
Setting the Foolproof data annotation ‘RequiredIfTrue’ ensures that MaidenName will be set as required if Married = true.
In addition to this, it includes a suite of required ‘if’ validators:
[RequiredIf] [RequiredIfNot] [RequiredIfTrue] [RequiredIfFalse] [RequiredIfEmpty] [RequiredIfNotEmpty] [RequiredIfRegExMatch] [RequiredIfNotRegExMatch]
And operator validators:
[Is] [EqualTo] [NotEqualTo] [GreaterThan] [LessThan] [GreaterThanOrEqualTo] [LessThanOrEqualTo]
