How do I use IValidatableObject

Question

I understand that IValidatableObject is used to validate an object in a way that lets one compare properties against each other  I d still like to have attributes to validate individual properties  but I want to ignore failures on some properties in certain cases  Am I trying to use it incorrectly in the case below   If not how do I implement this  public class ValidateMe   IValidatableObject        Required      public bool Enable   get  set          Range 1  5       public int Prop1   get  set          Range 1  5       public int Prop2   get  set         public IEnumerable lt ValidationResult gt  Validate ValidationContext validationContext                if   this Enable                           Return valid result here                 I don t care if Prop1 and Prop2 are out of range                if the whole object is not  quot enabled quot                                    else                          Check if Prop1 and Prop2 meet their range requirements here                and return accordingly

User · Answer

The thing i don t like about iValidate is it seems to only run AFTER all other validation   Additionally  at least in our site  it would run again during a save attempt   I would suggest you simply create a function and place all your validation code in that   Alternately for websites  you could have your  special  validation in the controller after the model is created     Example      public ActionResult Update  DataSourceRequest  DataSourceRequest request   Bind Exclude    Terminal    Driver driver                 if  db Drivers Where m   gt  m IDNumber    driver IDNumber  amp  amp  m ID    driver ID  Any                          ModelState AddModelError  Update   string Format  ID     0   is already in use   driver IDNumber                      if  db Drivers Where d   gt  d CarrierID    driver CarrierID                                  amp  amp  d FirstName Equals driver FirstName  StringComparison CurrentCultureIgnoreCase                                   amp  amp  d LastName Equals driver LastName  StringComparison CurrentCultureIgnoreCase                                   amp  amp   driver ID    0    d ID    driver ID   Any                          ModelState AddModelError  Update    Driver already exists for this carrier                       if  ModelState IsValid                        try

User · Answer

Quote from Jeff Handley s Blog Post on Validation Objects and Properties with Validator   When validating an object  the following process is applied in Validator ValidateObject   Validate property-level attributes If any validators are invalid  abort validation returning the failure s  Validate the object-level attributes If any validators are invalid  abort validation returning the failure s  If on the desktop framework and the object implements IValidatableObject  then call its Validate method and return any failure s    This indicates that what you are attempting to do won t work out-of-the-box because the validation will abort at step  2  You could try to create attributes that inherit from the built-in ones and specifically check for the presence of an enabled property  via an interface  before performing their normal validation  Alternatively  you could put all of the logic for validating the entity in the Validate method  You also could take a look a the exact implemenation of Validator class here

User · Answer

I liked cocogza s answer except that calling base IsValid resulted in a stack overflow exception as it would re-enter the IsValid method again and again  So I modified it to be for a specific type of validation  in my case it was for an e-mail address    AttributeUsage AttributeTargets Property   class ValidEmailAddressIfTrueAttribute   ValidationAttribute       private readonly string  nameOfBoolProp       public ValidEmailAddressIfTrueAttribute string nameOfBoolProp                 nameOfBoolProp   nameOfBoolProp             protected override ValidationResult IsValid object value  ValidationContext validationContext                if  validationContext    null                        return null                     var property   validationContext ObjectType GetProperty  nameOfBoolProp           if  property    null                        return new ValidationResult     nameOfBoolProp  not found                       var boolVal   property GetValue validationContext ObjectInstance  null            if  boolVal    null    boolVal GetType      typeof bool                         return new ValidationResult     nameOfBoolProp  not boolean                       if   bool boolVal                        var attribute   new EmailAddressAttribute  ErrorMessage      value  is not a valid e-mail address                 return attribute GetValidationResult value  validationContext                     return null            This works much better  It doesn t crash and produces a nice error message  Hope this helps someone

User · Answer

Just to add a couple of points   Because the Validate   method signature returns IEnumerable lt  gt   that yield return can be used to lazily generate the results - this is beneficial if some of the validation checks are IO or CPU intensive   public IEnumerable lt ValidationResult gt  Validate ValidationContext validationContext        if  this Enable                               if  this Prop1  gt  this Prop2                        yield return new ValidationResult  Prop1 must be larger than Prop2                Also  if you are using MVC ModelState  you can convert the validation result failures to ModelState entries as follows  this might be useful if you are doing the validation in a custom model binder    var resultsGroupedByMembers   validationResults      SelectMany vr   gt  vr MemberNames                          Select mn   gt  new   MemberName   mn                                                     Error   vr ErrorMessage          GroupBy x   gt  x MemberName    foreach  var member in resultsGroupedByMembers        ModelState AddModelError          member Key          string Join       member Select m   gt  m Error

User · Answer

I implemented a general usage abstract class for validation  using System  using System Collections Generic  using System ComponentModel DataAnnotations   namespace App Abstractions        Serializable      abstract public class AEntity               public int Id   get  set             public IEnumerable lt ValidationResult gt  Validate                         var vResults   new List lt ValidationResult gt                  var vc   new ValidationContext                  instance  this                  serviceProvider  null                  items  null                var isValid   Validator TryValidateObject                  instance  vc ObjectInstance                  validationContext  vc                  validationResults  vResults                  validateAllProperties  true                               if  true                                yield return new ValidationResult  Custom Validation   A Property Name string  optional                                               if   isValid                                foreach  var validationResult in vResults                                        yield return validationResult                                               yield break

User · Answer

First off  thanks to  paper1337 for pointing me to the right resources   I m not registered so I can t vote him up  please do so if anybody else reads this   Here s how to accomplish what I was trying to do   Validatable class   public class ValidateMe   IValidatableObject        Required      public bool Enable   get  set          Range 1  5       public int Prop1   get  set          Range 1  5       public int Prop2   get  set         public IEnumerable lt ValidationResult gt  Validate ValidationContext validationContext                var results   new List lt ValidationResult gt             if  this Enable                        Validator TryValidateProperty this Prop1                  new ValidationContext this  null  null    MemberName    Prop1                     results               Validator TryValidateProperty this Prop2                  new ValidationContext this  null  null    MemberName    Prop2                     results                   some other random test             if  this Prop1  gt  this Prop2                                results Add new ValidationResult  Prop1 must be larger than Prop2                                     return results            Using Validator TryValidateProperty   will add to the results collection if there are failed validations   If there is not a failed validation then nothing will be add to the result collection which is an indication of success   Doing the validation       public void DoValidation                 var toValidate   new ValidateMe                         Enable   true              Prop1   1              Prop2   2                     bool validateAllProperties   false           var results   new List lt ValidationResult gt              bool isValid   Validator TryValidateObject              toValidate              new ValidationContext toValidate  null  null               results              validateAllProperties           It is important to set validateAllProperties to false for this method to work   When validateAllProperties is false only properties with a  Required  attribute are checked   This allows the IValidatableObject Validate   method handle the conditional validations

User · Answer

The problem with the accepted answer is that it now depends on the caller for the object to be properly validated  I would either remove the RangeAttribute and do the range validation inside the Validate method or I would create a custom attribute subclassing RangeAttribute that takes the name of the required property as an argument on the constructor    For example    AttributeUsage AttributeTargets Property  AllowMultiple   false   class RangeIfTrueAttribute   RangeAttribute       private readonly string  NameOfBoolProp       public RangeIfTrueAttribute string nameOfBoolProp  int min  int max    base min  max                 NameOfBoolProp   nameOfBoolProp             public RangeIfTrueAttribute string nameOfBoolProp  double min  double max    base min  max                 NameOfBoolProp   nameOfBoolProp             protected override ValidationResult IsValid object value  ValidationContext validationContext                var property   validationContext ObjectType GetProperty  NameOfBoolProp           if  property    null              return new ValidationResult     NameOfBoolProp  not found             var boolVal   property GetValue validationContext ObjectInstance  null            if  boolVal    null    boolVal GetType      typeof bool               return new ValidationResult     NameOfBoolProp  not boolean             if   bool boolVal                        return base IsValid value  validationContext                     return null

[c#] How do I use IValidatableObject?

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