We Keep Coding

Pass Property of Class to ValidationAttribute

I am trying to write my own ValidationAttribute for which I want to pass the value of a parameter of my class to the ValidationAttribute. Very simple, if the boolean property is true, the property with the ValidationAttribute on top should not be null or empty.
My class:
public class Test
{
public bool Damage { get; set; }
[CheckForNullOrEmpty(Damage)]
public string DamageText { get; set; }
...
}
My Attribute:
public class CheckForNullOrEmpty: ValidationAttribute
{
private readonly bool _damage;
public RequiredForWanrnleuchte(bool damage)
{
_damage = damage;
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
string damageText = validationContext.ObjectType.GetProperty(validationContext.MemberName).GetValue(validationContext.ObjectInstance).ToString();
if (_damage == true && string.IsNullOrEmpty(damageText))
return new ValidationResult(ErrorMessage);
return ValidationResult.Success;
}
}
However, I cannot simply pass the property inside the class to the ValidationAttribute like that. What would be a solution to pass the value of that property?

Instead of passing the bool value to the CheckForNullOrEmptyAttribute, you should pass the name of the corresponding property; within the attribute, you then can retrieve this bool value from the object instance being validated.
The CheckForNullOrEmptyAttribute below, can be applied on your model as shown here.
public class Test
{
public bool Damage { get; set; }
[CheckForNullOrEmpty(nameof(Damage))] // Pass the name of the property.
public string DamageText { get; set; }
}
public class CheckForNullOrEmptyAttribute : ValidationAttribute
{
public CheckForNullOrEmptyAttribute(string propertyName)
{
PropertyName = propertyName;
}
public string PropertyName { get; }
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
var hasValue = !string.IsNullOrEmpty(value as string);
if (hasValue)
{
return ValidationResult.Success;
}
// Retrieve the boolean value.
var isRequired =
Convert.ToBoolean(
validationContext.ObjectInstance
.GetType()
.GetProperty(PropertyName)
.GetValue(validationContext.ObjectInstance)
);
if (isRequired)
{
return new ValidationResult(ErrorMessage);
}
return ValidationResult.Success;
}
}

Issue with custom DataAnnotation

I have a problem with a custom DataAnnotation.
public class RequiredInt32 : ValidationAttribute
{
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
if (value != null)
{
if (Convert.ToInt32(value) == 0)
{
return new ValidationResult("custom-message");
}
}
return ValidationResult.Success;
}
}
I have that code. If the condition is met, no returns "custom-message" , returns me "The field is invalid". For me return the message I want, I need to put it explicitly.
[RequiredInt32 (ErrorMessage = # "custom-message")]
What I have wrong and how can I do to have a default message. Thank you!

If you meant to customize formatting error message, you can define an attribute like this:
public class RequiredInt32 : ValidationAttribute
{
private const string _customFormat = "{0} is not valid";
private string _fieldName;
public RequiredInt32(string fieldName)
: base(_customFormat)
{
_fieldName = fieldName;
}
public override string FormatErrorMessage(string name)
{
return string.Format(ErrorMessageString, name);
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
if (value != null)
{
if (Convert.ToInt32(value) == 0)
{
return new ValidationResult(FormatErrorMessage(_fieldName));
}
}
return ValidationResult.Success;
}
}
Usage:
[RequiredInt32("MyField")]
public int NumberProperty {get;set;}

RequiredIf data annotation with enums

I have created a custom RequiredIf validator like this:
public class RequiredIfValidator : ValidationAttribute, IClientValidatable
{
RequiredAttribute _innerAttribute = new RequiredAttribute();
public string _dependentProperty { get; set; }
public object _targetValue { get; set; }
public RequiredIfValidator(string dependentProperty, object targetValue)
{
this._dependentProperty = dependentProperty;
this._targetValue = targetValue;
}
public override string FormatErrorMessage(string name)
{
return string.Format(CultureInfo.CurrentCulture, ErrorMessageString, name, _dependentProperty);
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
var field = validationContext.ObjectInstance.GetType().GetProperty(_dependentProperty);
if (field != null)
{
var dependentValue = field.GetValue(validationContext.ObjectInstance, null);
if ((dependentValue == null && _targetValue == null) ||(dependentValue.Equals(_targetValue)))
{
if (!_innerAttribute.IsValid(value))
{
return new ValidationResult(FormatErrorMessage(validationContext.DisplayName));
}
}
}
return ValidationResult.Success;
}
public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
{
var rule = new ModelClientValidationRule();
rule.ErrorMessage = FormatErrorMessage(metadata.GetDisplayName());
rule.ValidationType = "requiredif";
rule.ValidationParameters["dependentproperty"] = _dependentProperty;
rule.ValidationParameters["targetvalue"] = _targetValue;
yield return rule;
}
}
I have an enum with various test types like this:
public enum TestTypes
{
Hair = 1,
Urine = 2
}
My ViewModel has some properties like this:
public class TestViewModel
{
public TestTypes TestTypeId {get; set;}
[RequiredIfValidator("TestTypeId", TestTypes.Hair)]
public string HairSpecimenId {get; set;}
}
My custom RequiredIfValidator is not working in this scinario. Is it because of the enum data type? Any way to achieve this with enums

You logic in the IsValid() does not appear to be correct. It should be
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
if (value == null)
{
var otherProperty = validationContext.ObjectInstance.GetType().GetProperty(_dependentProperty);
var otherPropertyValue = otherProperty.GetValue(validationContext.ObjectInstance, null);
if (otherPropertyValue != null && otherPropertyValue.Equals(_targetValue ))
{
return new ValidationResult(FormatErrorMessage(validationContext.DisplayName));
}
}
return ValidationResult.Success;
}

MVC3 Custom validation

I have a model with property
[Display(Name = "Phone")]
public List<Phone> PhoneNumbers { get; set; }
I want to validate that List should be greater then 0
Suggest me the code.
/// <summary>
/// Atleast one phone number is required
/// </summary>
public sealed class DemographicPhoneNumberRequiredCheck : ValidationAttribute
{
public override bool IsValid(object value)
{
???????
}
}
Thanks.

You could use Count or Any:
public override bool IsValid(object value)
{
var PhoneNumbers = value as List<Phone>;
if (PhoneNumbers != null)
{
return PhoneNumbers.Count() > 0;
}
return false;
}
Or:
public override bool IsValid(object value)
{
var PhoneNumbers = value as List<Phone>;
if (PhoneNumbers != null)
{
return PhoneNumbers.Any();
}
}

Actually you have the value in your method:
public override bool IsValid(object value)
{
var phoneNumbers = value as List<Phone>;
if(phoneNumbers != null)
{
// perform the validation
}
}

How to create a custom attribute in Data Annotaion

How I can create custom attribute in Data Annotation?I want to set Control name assosiated with a property ad I don't find any suitable attribute.
How I can do this?
thanks

You must extend System.ComponentModel.DataAnnotations.ValidationAttribute
K. Scott Allen (of OdeToCode) has a great example where he builds a custom "GreaterThan" attribute.
http://odetocode.com/blogs/scott/archive/2011/02/21/custom-data-annotation-validator-part-i-server-code.aspx
Here is the snippet included inline though:
public class GreaterThanAttribute : ValidationAttribute
{
public GreaterThanAttribute(string otherProperty)
:base("{0} must be greater than {1}")
{
OtherProperty = otherProperty;
}
public string OtherProperty { get; set; }
public override string FormatErrorMessage(string name)
{
return string.Format(ErrorMessageString, name, OtherProperty);
}
protected override ValidationResult
IsValid(object firstValue, ValidationContext validationContext)
{
var firstComparable = firstValue as IComparable;
var secondComparable = GetSecondComparable(validationContext);
if (firstComparable != null && secondComparable != null)
{
if (firstComparable.CompareTo(secondComparable) < 1)
{
return new ValidationResult(
FormatErrorMessage(validationContext.DisplayName));
}
}
return ValidationResult.Success;
}
protected IComparable GetSecondComparable(
ValidationContext validationContext)
{
var propertyInfo = validationContext
.ObjectType
.GetProperty(OtherProperty);
if (propertyInfo != null)
{
var secondValue = propertyInfo.GetValue(
validationContext.ObjectInstance, null);
return secondValue as IComparable;
}
return null;
}
}