ASP NET MVC Conditional validation

Question

How to use data annotations to do a conditional validation on model   For example  lets say we have the following model  Person and Senior    public class Person        Required ErrorMessage             public string Name               get          set             public bool IsSenior               get          set             public Senior Senior               get          set           public class Senior        Required ErrorMessage          this should be conditional validation  based on the  IsSenior  value     public string Description               get          set            And the following view    lt    Html EditorFor m   gt  m Name   gt   lt    Html ValidationMessageFor m   gt  m Name   gt    lt    Html CheckBoxFor m   gt  m IsSenior   gt   lt    Html ValidationMessageFor m   gt  m IsSenior   gt    lt    Html CheckBoxFor m   gt  m Senior Description   gt   lt    Html ValidationMessageFor m   gt  m Senior Description   gt    I would like to be the  Senior Description  property conditional required field based on the selection of the  IsSenior  propery  true -  required   How to implement conditional validation in ASP NET MVC 2 with data annotations

User · Answer

You need to validate at Person level  not on Senior level  or Senior must have a reference to its parent Person  It seems to me that you need a self validation mechanism that defines the validation on the Person and not on one of its properties  I m not sure  but I don t think DataAnnotations supports this out of the box  What you can do create your own Attribute that derives from ValidationAttribute that can be decorated on class level and next create a custom validator that also allows those class-level validators to run   I know Validation Application Block supports self-validation out-of the box  but VAB has a pretty steep learning curve  Nevertheless  here s an example using VAB    HasSelfValidation  public class Person       public string Name   get  set        public bool IsSenior   get  set        public Senior Senior   get  set          SelfValidation      public void ValidateRange ValidationResults results                if  this IsSenior  amp  amp  this Senior    null  amp  amp               string IsNullOrEmpty this Senior Description                         results AddResult new ValidationResult                   A senior description is required                    this          null

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Thanks Merritt     I ve just updated this to MVC 3 in case anyone finds it useful  Conditional Validation in ASP NET MVC 3

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There s a much better way to add conditional validation rules in MVC3  have your model inherit IValidatableObject and implement the Validate method   public class Person   IValidatableObject       public string Name   get  set        public bool IsSenior   get  set        public Senior Senior   get  set         public IEnumerable lt ValidationResult gt  Validate ValidationContext validationContext                  if  IsSenior  amp  amp  string IsNullOrEmpty Senior Description                yield return new ValidationResult  Description must be supplied               Read more at Introducing ASP NET MVC 3  Preview 1

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Check out Simon Ince s Conditional Validation in MVC   I am working through his example project right now

User · Answer

I have solved this by handling the  ModelState  dictionary  which is contained by the controller  The ModelState dictionary includes all the members that have to be validated   Here is the solution   If you need to implement a conditional validation based on some field  e g  if A true  then B is required   while maintaining property level error messaging  this is not true for the custom validators that are on object level  you can achieve this by handling  ModelState   by simply removing unwanted validations from it      In some class       public bool PropertyThatRequiredAnotherFieldToBeFilled     get    set      Required ErrorMessage          public string DepentedProperty     get    set         class continues        In some controller action      if   PropertyThatRequiredAnotherFieldToBeFilled       this ModelState Remove  DepentedProperty             With this we achieve conditional validation  while leaving everything else the same     UPDATE   This is my final implementation  I have used an interface on the model and the action attribute that validates the model which implements the said interface  Interface prescribes the Validate ModelStateDictionary modelState  method  The attribute on action just calls the Validate modelState  on IValidatorSomething   I did not want to complicate this answer  so I did not mention the final implementation details  which  at the end  matter in production code

User · Answer

I ve been using this amazing nuget that does dynamic annotations ExpressiveAnnotations  You could validate any logic you can dream of   public string Email   get  set    public string Phone   get  set     RequiredIf  Email    null     RequiredIf  Phone    null     AssertThat  AgreeToContact    true    public bool  AgreeToContact   get  set

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There is now a framework that does this conditional validation  among other handy data annotation validations  out of the box  http   foolproof codeplex com   Specifically  take a look at the  RequiredIfTrue  IsSenior    validator   You put that directly on the property you want to validate  so you get the desired behavior of the validation error being associated to the  Senior  property   It is available as a NuGet package

User · Answer

You can disable validators conditionally by removing errors from ModelState   ModelState  DependentProperty   Errors Clear

User · Answer

Typical usage for conditional removal of error from Model State    Make conditional first part of controller action Perform logic to remove error from ModelState Do the rest of the existing logic  typically Model State validation  then everything else    Example   public ActionResult MyAction MyViewModel vm           perform conditional test        if true  then remove from ModelState  e g  ModelState Remove  MyKey           Do typical model state validation  inside following if             if   ModelState IsValid          Do rest of logic  e g  fetching  saving   In your example  keep everything as is and add the logic suggested to your Controller s Action   I m assuming your ViewModel passed to the controller action has the Person and Senior Person objects with data populated in them from the UI

User · Answer

I had the same problem yesterday but I did it in a very clean way which works for both client side and server side validation   Condition  Based on the value of other property in the model  you want to make another property required  Here is the code  public class RequiredIfAttribute   RequiredAttribute       private String PropertyName   get  set        private Object DesiredValue   get  set         public RequiredIfAttribute String propertyName  Object desiredvalue                PropertyName   propertyName          DesiredValue   desiredvalue             protected override ValidationResult IsValid object value  ValidationContext context                Object instance   context ObjectInstance          Type type   instance GetType            Object proprtyvalue   type GetProperty PropertyName  GetValue instance  null           if  proprtyvalue ToString      DesiredValue ToString                          ValidationResult result   base IsValid value  context               return result                    return ValidationResult Success            Here PropertyName is the property on which you want to make your condition DesiredValue is the particular value of the PropertyName  property  for which your other property has to be validated for required  Say you have the following  public class User       public UserType UserType   get  set          RequiredIf  UserType   UserType Admin  ErrorMessageResourceName    PasswordRequired   ErrorMessageResourceType   typeof ResourceString        public string Password               get          set            At last but not the least   register adapter for your attribute so that it can do client side validation   I put it in global asax  Application Start    DataAnnotationsModelValidatorProvider RegisterAdapter typeof RequiredIfAttribute  typeof RequiredAttributeAdapter

User · Answer

I had the same problem  needed a modification of  Required  attribute - make field required in dependence of http request The solution was similar to Dan Hunex answer  but his solution didn t work correctly  see comments   I don t use unobtrusive validation  just MicrosoftMvcValidation js out of the box  Here it is  Implement your custom attribute   public class RequiredIfAttribute   RequiredAttribute        public RequiredIfAttribute   You can put here pararmeters if You need  as seen in other answers of this topic                      protected override ValidationResult IsValid object value  ValidationContext context               You can put your logic here             return ValidationResult Success   I don t need its server-side so it always valid on server but you can do what you need             Then you need to implement your custom provider to use it as an adapter in your global asax  public class RequreIfValidator   DataAnnotationsModelValidator  lt RequiredIfAttribute gt         ControllerContext ccontext      public RequreIfValidator ModelMetadata metadata  ControllerContext context  RequiredIfAttribute attribute           base metadata  context  attribute                ccontext   context    I need only http request          override it for custom client-side validation       public override IEnumerable lt ModelClientValidationRule gt  GetClientValidationRules                                  here you can customize it as you want          ModelClientValidationRule rule   new ModelClientValidationRule                           ErrorMessage   ErrorMessage        and here is what i need on client side - if you want to make field required on client side just make ValidationType  required                   ValidationType   ccontext HttpContext Request  extOperation       2      required     none                        return new ModelClientValidationRule     rule                And modify your global asax with a line  DataAnnotationsModelValidatorProvider RegisterAdapter typeof RequiredIfAttribute   typeof RequreIfValidator      and here it is   RequiredIf  public string NomenclatureId   get  set      The main advantage for me is that I don t have to code custom client validator as in case of unobtrusive validation  it works just as  Required   but only in cases that you want

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I m using MVC 5 but you could try something like this   public DateTime JobStart   get  set      AssertThat  StartDate  gt   JobStart   ErrorMessage    Time Manager may not begin before job start date     DisplayName  Start Date     Required  public DateTime  StartDate   get  set      In your case you would say something like  IsSenior    true   Then you just need to check the validation on your post action

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