Custom Validation Attribute Multiple Times on same field

Question

How can I use Same Custom Validation Attribute Multiple Times on Same Field or simply enable AllowMultiple=true, for both server side and client side validation??

I have a following Custom Validation Attribute:

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, 
        AllowMultiple = true, Inherited = true)]
public class RequiredIfAttribute : ValidationAttribute,IClientValidatable
{
    public RequiredIfAttribute(string dependentProperties, 
     string dependentValues = "",
     string requiredValue = "val")
     {
     }
}

Where in dependentProperties I can specify multiple dependant properties seperated by comma, in dependentValues I can specify for which values of dependant properties validation should process and finally in requiredValue I can specify expected value for the field to be validated.

In my model there are two properties LandMark, PinCode and I want to use validation as follows:

public string LandMark { get; set; }
[RequiredIf("LandMark","XYZ","500500")]
[RequiredIf("LandMark", "ABC", "500505")]
public string PinCode { get; set; }

The values here are just for example, as per it seems I can add the attribute multiple times and don't get any compile error, I have implemented TypeID in attribute and it works well from serverside if I remove client validation from it. But when I am implementing IClientValidatable on the attribute, it gives me an error:

"Validation type names in unobtrusive client validation rules must be unique."

Any help how can I solve it??

Answer 1

Finally here I found the answer my-self. Look at following article for solution http://www.codeproject.com/KB/validation/MultipleDataAnnotations.aspx

Answer 2

The link in the accepted answer ( http://www.codeproject.com/KB/validation/MultipleDataAnnotations.aspx ) is buggy, and someone else has written an errata here which I would recommend reading first. The answer above does not handle inheritance. I believe this alternate solution has some advantages (including support of inheritance), but remains far from perfect code - improvements appreciated.

this C# uses Json.NET and Stuart Leeks HTML Attribute provider

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web.Mvc;
using Newtonsoft.Json;

namespace DabTrial.Infrastructure.Validation
{
    [AttributeUsage(AttributeTargets.Property, AllowMultiple = true, Inherited = true)]
    public abstract class MultipleValidationAttribute : ValidationAttribute, IMetadataAware
    {
        private class Validation
        {
            public ICollection<string> ErrorMessage { get; set; }
            public IDictionary<string, ICollection<object>> Attributes { get; set; }
        }
        private object _typeId = new object();
        public const string attributeName = "multipleValidations";
        public MultipleValidationAttribute()
        {
        }
        public override object TypeId
        {
            get
            {
                return this._typeId;
            }
        }
        public void OnMetadataCreated(ModelMetadata metadata)
        {
            Dictionary<string, Validation> allMultis;
            if (metadata.AdditionalValues.ContainsKey(attributeName))
            {
                allMultis = (Dictionary<string, Validation>)metadata.AdditionalValues[attributeName];
            }
            else
            {
                allMultis = new Dictionary<string, Validation>();
                metadata.AdditionalValues.Add(attributeName, allMultis);
            }
            foreach (var result in GetClientValidationRules(metadata))
            {
                if (allMultis.ContainsKey(result.ValidationType))
                {
                    var thisMulti = allMultis[result.ValidationType];
                    thisMulti.ErrorMessage.Add(result.ErrorMessage);
                    foreach (var attr in result.ValidationParameters)
                    {
                        thisMulti.Attributes[attr.Key].Add(attr.Value);
                    }
                }
                else
                {
                    var thisMulti = new Validation
                    {
                        ErrorMessage = new List<string>(),
                        Attributes = new Dictionary<string, ICollection<object>>()
                    };
                    allMultis.Add(result.ValidationType, thisMulti);
                    thisMulti.ErrorMessage.Add(result.ErrorMessage);
                    foreach (var attr in result.ValidationParameters)
                    {
                        var newList = new List<object>();
                        newList.Add(attr.Value);
                        thisMulti.Attributes.Add(attr.Key, newList);
                    }
                }
            }
        }

        public static IEnumerable<KeyValuePair<string, object>> GetAttributes(ModelMetadata metadata)
        {
            if (!metadata.AdditionalValues.ContainsKey(attributeName))
            {
                return null;
            }
            var returnVar = new List<KeyValuePair<string, object>>();
            returnVar.Add(new KeyValuePair<string,object>("data-val", true));
            var allMultis = (Dictionary<string, Validation>)metadata.AdditionalValues[attributeName];
            foreach (var multi in allMultis)
            {
                string valName = "data-val-" + multi.Key;
                returnVar.Add(new KeyValuePair<string,object>(valName, JsonConvert.SerializeObject(multi.Value.ErrorMessage)));
                returnVar.AddRange(multi.Value.Attributes.Select(a=>new KeyValuePair<string,object>(valName + '-' + a.Key, JsonConvert.SerializeObject(a.Value))));
            }
            return returnVar;
        }
        public virtual IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata,
                                                                               ControllerContext context)
        {
            throw new NotImplementedException("This function must be overriden");
        }
        public virtual IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata)
        {
            return GetClientValidationRules(metadata, null);
        }
    }
}

the Global.asax contains the code

HtmlAttributeProvider.Register((metadata) =>
{
    return MultipleValidationAttribute.GetAttributes(metadata);
});

and the JavaScript (within a custom validators function)

function setMultiValidationValues(options, ruleName, values) {
    var i = 0, thisRule;
    for (; i < values.length; i++) {
        thisRule = (i == 0) ? ruleName : ruleName + i;
        options.messages[thisRule] = values[i].message;
        delete values[i].message;
        options.rules[thisRule] = values[i];
        if (ruleName !== thisRule) {
            (function addValidatorMethod() {
                var counter = 0;
                if (!$.validator.methods[ruleName]) {
                    if (++counter > 10) { throw new ReferenceError(ruleName + " is not defined"); }
                    setTimeout(addValidatorMethod, 100);
                    return;
                }
                if (!$.validator.methods[thisRule]) { $.validator.addMethod(thisRule, $.validator.methods[ruleName]); }
            })();
        }
    }
}
function transformValidationValues(options) {
    var rules = $.parseJSON(options.message),
        propNames = [], p, utilObj,i = 0,j, returnVar=[];
    for (p in options.params) {
        if (options.params.hasOwnProperty(p)) {
            utilObj = {};
            utilObj.key = p;
            utilObj.vals = $.parseJSON(options.params[p]);
            propNames.push(utilObj);
        }
    }
    for (; i < rules.length; i++) {
        utilObj = {};
        utilObj.message = rules[i];
        for (j=0; j < propNames.length; j++) {
            utilObj[propNames[j].key] = propNames[j].vals[i];
        }
        returnVar.push(utilObj);
    }
    return returnVar;
}

An example of its use is below: C#

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Text.RegularExpressions;
using System.Web.Mvc;

namespace DabTrial.Infrastructure.Validation
{
    [AttributeUsage(AttributeTargets.Property, AllowMultiple = true, Inherited = true)]
    public class RegexCountAttribute : MultipleValidationAttribute
    {
        # region members
        private string _defaultErrorMessageFormatString;
        protected readonly string _regexStr;
        protected readonly RegexOptions _regexOpt;
        private int _minimumCount=0;
        private int _maximumCount=int.MaxValue;
        #endregion
        #region properties
        public int MinimumCount 
        {
            get { return _minimumCount; } 
            set 
            {
                if (value < 0) { throw new ArgumentOutOfRangeException(); }
                _minimumCount = value; 
            } 
        }
        public int MaximumCount
        {
            get { return _maximumCount; }
            set 
            {
                if (value < 0) { throw new ArgumentOutOfRangeException(); }
                _maximumCount = value; 
            }
        }
        private string DefaultErrorMessageFormatString
        {
            get
            {
                if (_defaultErrorMessageFormatString == null)
                {
                    _defaultErrorMessageFormatString = string.Format(
                        "{{0}} requires a {0}{1}{2} match(es) to regex {3}", 
                        MinimumCount>0?"minimum of "+ MinimumCount:"",
                        MinimumCount > 0 && MaximumCount< int.MaxValue? " and " : "",
                        MaximumCount<int.MaxValue?"maximum of "+ MaximumCount:"",
                        _regexStr);
                }
                return _defaultErrorMessageFormatString;
            }
            set
            {
                _defaultErrorMessageFormatString = value;
            }

        }
        #endregion
        #region instantiation
        public RegexCountAttribute(string regEx, string defaultErrorMessageFormatString = null, RegexOptions regexOpt = RegexOptions.None)
        {
#if debug
            if (minimumCount < 0) { throw new ArgumentException("the minimum value must be non-negative"); }
#endif
            _regexStr = regEx;
            DefaultErrorMessageFormatString = defaultErrorMessageFormatString;
            _regexOpt = regexOpt;
        }
        #endregion
        #region methods

        protected override ValidationResult IsValid(object value,
                                                    ValidationContext validationContext)
        {
            var instr = (string)value;
            int matchCount = 0;
            if (MinimumCount > 0 && instr != null)
            {
                Match match = new Regex(_regexStr,_regexOpt).Match(instr);
                while (match.Success && ++matchCount < MinimumCount)
                {
                   match = match.NextMatch();
                }
                if (MaximumCount != int.MaxValue)
                {
                    while (match.Success && ++matchCount <= MaximumCount)
                    {
                        match = match.NextMatch();
                    }
                }
            }
            if (matchCount >= MinimumCount && matchCount <=MaximumCount)
            {
                return ValidationResult.Success;
            }
            string errorMessage = GetErrorMessage(validationContext.DisplayName);
            return new ValidationResult(errorMessage);
        }
        protected string GetErrorMessage(string displayName)
        {
            return ErrorMessage ?? string.Format(DefaultErrorMessageFormatString,
                displayName,
                MinimumCount);
        }
        private bool HasFlag(RegexOptions options, RegexOptions flag)
        {
            return ((options & flag) == flag);
        }
        private string RegexpModifier
        {
            get 
            {
                string options = string.Empty;
                if (HasFlag(_regexOpt, RegexOptions.IgnoreCase)) { options += 'i'; }
                if (HasFlag(_regexOpt, RegexOptions.Multiline)) { options += 'm'; }
                return options;
            }
        }
        public override IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata)
        {
            var returnVal = new ModelClientValidationRule {
                ErrorMessage = GetErrorMessage(metadata.DisplayName),
                ValidationType = "regexcount",
            };
            returnVal.ValidationParameters.Add("min",MinimumCount);
            returnVal.ValidationParameters.Add("max",MaximumCount);
            returnVal.ValidationParameters.Add("regex",_regexStr);
            returnVal.ValidationParameters.Add("regexopt", RegexpModifier);
            yield return returnVal;
        }
        #endregion
    }
    public class MinNonAlphanum : RegexCountAttribute
    {
        public MinNonAlphanum(int minimum) : base("[^0-9a-zA-Z]", GetDefaultErrorMessageFormatString(minimum)) 
        {
            this.MinimumCount = minimum;
        }
        private static string GetDefaultErrorMessageFormatString(int min)
        {
            if (min == 1)
            {
                return "{0} requires a minimum of {1} character NOT be a letter OR number";
            }
            return "{0} requires a minimum of {1} characters NOT be a letter OR number";
        }
    }
    public class MinDigits : RegexCountAttribute
    {
        public MinDigits(int minimum) : base(@"\d", GetDefaultErrorMessageFormatString(minimum)) 
        {
            this.MinimumCount = minimum;
        }
        private static string GetDefaultErrorMessageFormatString(int min)
        {
            if (min == 1)
            {
                return "{0} requires a minimum of {1} character is a number";
            }
            return "{0} requires a minimum of {1} characters are numbers";
        }
    }
}

JavaScript:

$.validator.addMethod("regexcount", function (value, element, params) {
    var matches = (value.match(params.regex)||[]).length
    return  matches >= params.min && matches <= params.max;
});
$.validator.unobtrusive.adapters.add("regexcount", ["min", "max", "regex", "regexopt"], function (options) {
    var args = transformValidationValues(options), i=0;
    for (; i < args.length; i++) {
        args[i].regex = new RegExp(args[i].regex, args[i].regexopt);
        delete args[i].regexopt;
    }
    setMultiValidationValues(options, "regexcount", args);
});

Answer 3

The Problem

Validation Attributes have two environments they can validate against:

1. Server
2. Client

Server Validation - Multiple Attributes Easy

If you have any attribute with:

[AttributeUsage(AttributeTargets.Property, )]
public class RequiredIfAttribute : 

And have put it on your class property like this:

public class Client
{
    public short ResidesWithCd { get; set; };

    
    public string ResidesWithOther { get; set; }
}

Then anytime the Server goes to validate an object (ex. ModelState.IsValid , it will check every ValidationAttribute on each property and call .IsValid() to determine validity. This will work fine, even if AttributeUsage . AllowMultiple is set to true.

Client Validation - HTML Attribute Bottleneck

If you enable client side by implementing IClientValidatable like this:

public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)    
{
    var modelClientValidationRule = new ModelClientValidationRule
    {
        ValidationType = ,
        ErrorMessage = ErrorMessageString
    };
    modelClientValidationRule.ValidationParameters.Add(, prop.PropName);
    modelClientValidationRule.ValidationParameters.Add(, prop.CompValues);

    return new List<ModelClientValidationRule> { modelClientValidationRule };
}

Then ASP.NET will emit the following HTML when generated:
^{(As long as ClientValidationEnabled & UnobtrusiveJavaScriptEnabled are enabled)}

<input class="form-control" type="text" value=""
       id="Client_CommunicationModificationDescription" 
       name="Client.CommunicationModificationDescription" 
        ="Communication Modification Description is required." ="CommunicationModificationCd" ="99" >

Data Attributes are the only vehicle we have for dumping rules into the client side validation engine which will search for any attributes on the page via a built in or custom adapter . And once part of the set of client side rules, it'll be able to determine the validity of each parsed rule with a built in or custom method .

So we can tall jQuery Validate Unobtrusive to look for and parse these attributes by adding a custom adapter which will add a validation rule to the engine:

// hook up to client side validation
$.validator.unobtrusive.adapters.add(, [, ], function (options) {
    options.rules[] = {
        id: '#' + options.params.,
        values: JSON.parse(options.params.)
    };
    options.messages['requiredif'] = options.;
});

We can then tell that rule how function and determine validity by adding a custom method like this which will add a custom way to evaluate requiredif rules (as opposed to date rules or regex rules) which will rely on the parameters we loaded earlier through the adapter:

// test validity
$.validator.addMethod(, function (value, element, params) {
    var targetHasCondValue = targetElHasValue(params.id, params.value);
    var requiredAndNoValue = targetHasCondValue && !value; // true -> :(
    var passesValidation = !requiredAndNoValue;            // true -> :)
    return passesValidation;
}, '');

Which all operates like this:

Solution

So, what have we learned? Well, if we want the same rule to appear multiple times on the same element, the adapter would have to see the exact set of rules multiple times per element, with no way to differentiate between each instance within multiple sets. Further, ASP.NET won't render the same attribute name multiple times since it's not valid html.

So, we either need to:

1. Collapse all the client side rules into a single mega attribute with all the info
2. Rename attributes with each instance number and then find a way to parse them in sets.

I'll explore Option One (emitting a single client side attribute), which you could do a couple ways:

1. Create a single Attribute that takes in multiple elements to validate on the server client
2. Keep multiple distinct server side attributes and then merge all attributes via reflection before emitting to the client

In either case you will have to re-write the client side logic (adapter/method) to take an array of values, instead of a single value at a time.

To we'll build/transmit a JSON serialized object that looks like this:

var props = [
  {
    PropName: "RoleCd",
    CompValues: ["2","3","4","5"]
  },
  {
    PropName: "IsPatient",
    CompValues: ["true"]
  }
]

Scripts/ValidateRequiredIfAny.js

Here's how we'll handle that in client side adapter / method:

// hook up to client side validation
$.validator.unobtrusive.adapters.add("requiredifany", ["props"], function (options) {
    options.rules["requiredifany"] = { props: options.params.props };
    options.messages["requiredifany"] = options.message;
});

// test validity
$.validator.addMethod("requiredifany", function (value, element, params) {
    var reqIfProps = JSON.parse(params.props);
    var anytargetHasValue = false;

    $.each(reqIfProps, function (index, item) {
        var targetSel = "#" + buildTargetId(element, item.PropName);
        var $targetEl = $(targetSel);
        var targetHasValue = elHasValue($targetEl, item.CompValues);

        if (targetHasValue) {
            anytargetHasValue = true;
            return ;
        }
    });

    var valueRequired = anytargetHasValue;
    var requiredAndNoValue = valueRequired && !value; // true -> :(
    var passesValidation = !requiredAndNoValue;       // true -> :)
    return passesValidation;

}, "");

// UTILITY METHODS

function buildTargetId(currentElement, targetPropName) {
    // https://stackoverflow.com/a/39725539/1366033
    // we are only provided the name of the target property
    // we need to build it's ID in the DOM based on a couple assumptions
    // derive the stacking context and depth based on the current element's ID/name
    // append the target property's name to that context

                                                // currentElement.name i.e. Details[0].DosesRequested
    var curId = currentElement.id;              // get full id         i.e. Details_0__DosesRequested
    var context = curId.replace(/[^_]+$/, "");  // remove last prop    i.e. Details_0__
    var targetId = context + targetPropName;    // build target ID     i.e. Details_0__OrderIncrement

    // fail noisily
    if ($("#" + targetId).length === 0)
        console.error(
            "Could not find id '" + targetId +
            "' when looking for '" + targetPropName +
            "'  on originating element '" + curId + "'");

    return targetId;
}

function elHasValue($el, values) {
    var isCheckBox = $el.is(":checkbox,:radio");
    var isChecked = $el.is(":checked");
    var inputValue = $el.val();
    var valueInArray = $.inArray(String(inputValue), values) > -1;

    var hasValue = (!isCheckBox || isChecked) && valueInArray;

    return hasValue;
};

Models/RequiredIfAttribute.cs

On the server side, we'll validate attributes like normal, but when we got to build the client side attributes, we'll look for all attributes and build one mega attribute

using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Reflection;
using System.Web.Helpers;
using System.Web.Mvc;

[AttributeUsage(AttributeTargets.Property, AllowMultiple = true)]
public class RequiredIfAttribute : ValidationAttribute, IClientValidatable
{

    public PropertyNameValues TargetProp { get; set; }

    public RequiredIfAttribute(string compPropName, string[] compPropValues, string msg) : base(msg)
    {
        this.TargetProp = new PropertyNameValues()
        {
            PropName = compPropName,
            CompValues = compPropValues
        };
    }
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        PropertyInfo compareProp = validationContext.ObjectType.GetProperty(TargetProp.PropName);
        var compPropVal = compareProp.GetValue(validationContext.ObjectInstance, null);
        string compPropValAsString = compPropVal?.ToString().ToLower() ?? "";
        var matches = TargetProp.CompValues.Where(v => v == compPropValAsString);
        bool needsValue = matches.Any();

        if (needsValue)
        {
            if (value == null || value.ToString() == "" || value.ToString() == "0")
            {
                return new ValidationResult(FormatErrorMessage(null));
            }
        }

        return ValidationResult.Success;
    }


    public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
    {
        // at this point, who cares that we're on this particular instance - find all instances
        PropertyInfo curProp = metadata.ContainerType.GetProperty(metadata.PropertyName);
        RequiredIfAttribute[] allReqIfAttr = curProp.GetCustomAttributes<RequiredIfAttribute>().ToArray();

        // emit validation attributes from all simultaneously, otherwise each will overwrite the last
        PropertyNameValues[] allReqIfInfo = allReqIfAttr.Select(x => x.TargetProp).ToArray();
        string allReqJson = Json.Encode(allReqIfInfo);

        var modelClientValidationRule = new ModelClientValidationRule
        {
            ValidationType = "requiredifany",
            ErrorMessage = ErrorMessageString
        };

        // add name for jQuery parameters for the adapter, must be LOWERCASE!
        modelClientValidationRule.ValidationParameters.Add("props", allReqJson);

        return new List<ModelClientValidationRule> { modelClientValidationRule };
    }
}

public class PropertyNameValues
{
    public string PropName { get; set; }
    public string[] CompValues { get; set; }
}

Then we can bind that to our model by applying multiple attributes simultaneously:

[RequiredIf(nameof(RelationshipCd), new[] { 1,2,3,4,5 }, "Mailing Address is required.")]
[RequiredIf(nameof(IsPatient), new[] { "true" },"Mailing Address is required.")]
public string MailingAddressLine1 { get; set; }

Further Reading

• ASP.NET MVC custom multiple fields validation by Stephen Muecke
• Unobtrusive Client Validation in ASP.NET MVC 3 by Brad Wilson