How to use same Custom Validation Attribute mutiple times on a property with client side unobtrusive validation in mvc

A week ago, I had a task about checking one date field [field1] with another date field [field2] and make sure that field1 is earlier than field2, we already have had datecompare custom validation attribute and it was supposed to be an easy one and take a tick to add this validation!

When I looked at Model ,I noticed that field1 already has datecompare attribute and it has been checked with other field [field3] and it checks field1 is after field3.

So I decided to set AllowMultiple = true in attribute usage of my customattribute(datecompareattribute) and override TypeId

AllowMultiple = true in AttributeUsage Allow Multiple Gets or sets a Boolean value indicating  whether more than one instance of the indicated attribute can be specified for a single program element. [AttributeUsage(AttributeTargets.Property, AllowMultiple = true, Inherited = true)]

Override TypeId in attribute private object _typeId = new object(); public override object TypeId {        get { return _typeId; } }

I said to myself how smart I am ;) but after running project I got this bug

Validation type names in unobtrusive client validation rules must be unique. The following validation type was seen more than once [InvalidOperationException: Validation type names in unobtrusive client validation rules must be unique. The following validation type was seen more than once: ....]

with a quick research I found a very impressive post(http://www.codeproject.com/KB/validation/MultipleDataAnnotations.aspx) about it. Thanks to the author for sharing that. Everything is fine and you can use it freely. except three issues which it has and I’m describing now.

1- It only can accept 26 same attribute on a field.

It adds ‘a’ to ‘z’ at the end of attribute name to make it unique. I think it is alright but if you are crazy enough to have more than 26 same attribute on a field so you need to change a way to create unique id for each attribute, go for it and then share your way for us :D

2-Remove static when you defining countPerField!

//To avoid multiple rules with same name     public static Dictionary<string, int> countPerField = null;

 Special thanks to one of our tech leads who found this!

comment out below part in htmlhelper

string element = html.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(                  ExpressionHelper.GetExpressionText(expression));         string Key = html.ViewData.Model.ToString() + "." + element;         RequiredIfAttribute.countPerField.Remove(Key);         if (RequiredIfAttribute.countPerField.Count == 0)             RequiredIfAttribute.countPerField = null;

adding an extra property (uniquesuffix) in your attribute instead of generating unique id so remove this part to

int count = 0; string Key = metadata.ContainerType.FullName + "." + metadata.GetDisplayName(); if(countPerField==null)        countPerField = new Dictionary<string, int>();         if (countPerField.ContainsKey(Key))         { count = ++countPerField[Key];         }         else          countPerField.Add(Key, count);

and only keep below part plus passing your new property

yield return new RequiredIfValidationRule (string.Format(ErrorMessageString, metadata.GetDisplayName()),requiredFieldValue,Props,Vals,_uniquesuffix);

and set unique id with help of your new property

//string tmp = count == 0 ? "" : Char.ConvertFromUtf32(96 + count);         ErrorMessage = errorMessage;       //  ValidationType = "requiredif"+tmp;         ValidationType = "requiredif"+uniquesuffix

3- Last one is the way to show proper error message.

You don't need to add extra property to keep error messages

var reqIfMultipleValidator = function (value, element, params) {         var others = params.others.split('!');         var reqVals = params.reqval.split('!');         var msgs = params.errorMsgs.split('!');         var errMsg = "";         var values = null;         if (params.values + "" != "")             values = params.values.split('!')         var retVal = true;         var errorIndex=0;         $.each(others, function (index, val) {             var myParams = { "others": val, "reqval": reqVals[index],                              "values": values[index] };             retVal = reqIfValidator(value, element, myParams);            if (retVal === false) {                                          errorIndex=index;                 return false;             }         });               var errormessages=$(element).data('valrequiredifmultiple').split('!');         if (retVal === false) {             var evalStr = "this.settings.messages." + $(element).attr("name") +                      ".requiredifmultiple='" + errormessages[errorIndex] + "'";             eval(evalStr);         }         return retVal;        };