ASP MVC 2 Validation : Passing Javascript code to the client - validation

I am writing a custom validation attribute
It does conditional validation between two fields
When I create my rule, one of the things that I could not solve is how to pass javascript code through ValidationParameters
Usually, I just do
ValidationParameters["Param1"] = "{ required :function(element) { return $("#age").val() < 13;) }"
However, the MicrosoftMvcJQueryValidation.js routines trnasforms this to
Param1 = "{ required :function(element) { return $("#age").val() < 13;) }"
I could use Param1.eval() in Javascript. This will evaluates and executes the code but I just want to evalute the code and execute it later
JSON parser does not parse string contening Javascript code
So I am asking here for any idea

Not sure how you would inject javascript as you describe, but you may want to consider using the custom validation pattern for ASP.NET MVC 2.
Important pieces are the ValidationAttribute, DataAnnotationsModelValidator, registering the validator in Application_Start with DataAnnotationsModelValidatorProvider.RegisterAdapter, and the client side Sys.Mvc.ValidatorRegistry.validators function collection to register your client side validation code.
Here's the example code from my post.
[RegularExpression("[\\S]{6,}", ErrorMessage = "Must be at least 6 characters.")]
public string Password { get; set; }
[StringLength(128, ErrorMessage = "Must be under 128 characters.")]
[MinStringLength(3, ErrorMessage = "Must be at least 3 characters.")]
public string PasswordAnswer { get; set; }
public class MinStringLengthAttribute : ValidationAttribute
{
public int MinLength { get; set; }
public MinStringLengthAttribute(int minLength)
{
MinLength = minLength;
}
public override bool IsValid(object value)
{
if (null == value) return true; //not a required validator
var len = value.ToString().Length;
if (len < MinLength)
return false;
else
return true;
}
}
public class MinStringLengthValidator : DataAnnotationsModelValidator<MinStringLengthAttribute>
{
int minLength;
string message;
public MinStringLengthValidator(ModelMetadata metadata, ControllerContext context, MinStringLengthAttribute attribute)
: base(metadata, context, attribute)
{
minLength = attribute.MinLength;
message = attribute.ErrorMessage;
}
public override IEnumerable<ModelClientValidationRule> GetClientValidationRules()
{
var rule = new ModelClientValidationRule
{
ErrorMessage = message,
ValidationType = "minlen"
};
rule.ValidationParameters.Add("min", minLength);
return new[] { rule };
}
}
protected void Application_Start()
{
RegisterRoutes(RouteTable.Routes);
DataAnnotationsModelValidatorProvider.RegisterAdapter(typeof(MinStringLengthAttribute), typeof(MinStringLengthValidator));
}
Sys.Mvc.ValidatorRegistry.validators["minlen"] = function(rule) {
//initialization
var minLen = rule.ValidationParameters["min"];
//return validator function
return function(value, context) {
if (value.length < minLen)
return rule.ErrorMessage;
else
return true; /* success */
};
};

Related

Does the IClientValidator support input file?

Edit
I found that the problem is that View Components are unable to have an #section (see ViewComponent and #Section #2910 ) so adding custom client-side validation using the unobtrusive library seems imposible (or very complex). Moreover, the inability of including the required javascript into a View Component makes me regret of following this approach to modularize my app in the first place...
I am learning to make custom validation attributes with client-side support. I was able to implement a custom validator for a string property and it works pretty well, but when I tried to make one for input file it doesn't work (i.e. when I select a file in my computer, the application doesn't display the validation messages. The server-side validation works. Here is some code that shows my implementation.
The class of the model
public class UploadPanelModel
{
public int? ID { get; set; }
public string Title { get; set; }
public string Description { get; set; } //Raw HTML with the panel description
[FileType(type: "application/pdf")]
[FileSize(maxSize: 5000000)]
public IFormFile File { get; set; }
public byte[] FileBytes { get; set; }
public ModalModel Modal { get; set; } //Only used if the Upload panel uses a modal.
The validator
public class FileSizeAttribute : ValidationAttribute, IClientModelValidator
{
private long _MaxSize { get; set; }
public FileSizeAttribute (long maxSize)
{
_MaxSize = maxSize;
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
UploadPanelModel panel = (UploadPanelModel)validationContext.ObjectInstance;
return (panel.File==null || panel.File.Length <= _MaxSize) ? ValidationResult.Success : new ValidationResult(GetFileSizeErrorMessage(_MaxSize));
}
private string GetFileSizeErrorMessage(long maxSize)
{
double megabytes = maxSize / 1000000.0;
return $"El archivo debe pesar menos de {megabytes}MB";
}
public void AddValidation(ClientModelValidationContext context)
{
if(context == null)
{
throw new ArgumentNullException(nameof(context));
}
MergeAttribute(context.Attributes, "data-val", "true");
MergeAttribute(context.Attributes, "data-val-filesize", GetFileSizeErrorMessage(_MaxSize));
var maxSize = _MaxSize.ToString();
MergeAttribute(context.Attributes, "data-val-filesize-maxsize", maxSize);
}
private bool MergeAttribute(IDictionary<string, string> attributes, string key, string value)
{
if (attributes.ContainsKey(key))
{
return false;
}
attributes.Add(key, value);
return true;
}
}
The javascript in the Razor View
#section Scripts{
#{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
<script type="text/javascript">
$.validator.addMethod('filesize',
function (value, element, params) {
var size = $((params[0]).val()).size(),
maxSize = params[1];
if (size < maxSize) {
return false;
}
else {
return false;
}
}
);
$.validator.unobtrusive.adapters.add('filesize',
['maxSize'],
function (options) {
var element = $(options.form).find('input#File')[0];
options.rules['filesize'] = [element, options.params['maxSize']];
options.messages['filesize'] = options.message;
}
);
</script>
I always return false in the javascript method to force the application to show the validation error regardless the chosen file, but it still doesn't work.
Your addMethod() function will be throwing an error because params[0] is not a jQuery object and has no .val() (you also have the $ in the wrong place). You would need to use
var size = params[0].files[0].size;
However I suggest you write you scripts as
$.validator.unobtrusive.adapters.add('filesize', ['maxsize'], function (options) {
options.rules['filesize'] = { maxsize: options.params.maxsize };
if (options.message) {
options.messages['filesize'] = options.message;
}
});
$.validator.addMethod("filesize", function (value, element, param) {
if (value === "") {
return true;
}
var maxsize = parseInt(param.maxsize);
if (element.files != undefined && element.files[0] != undefined && element.files[0].size != undefined) {
var filesize = parseInt(element.files[0].size);
return filesize <= maxsize ;
}
return true; // in case browser does not support HTML5 file API
});

JQuery custom validation attribute MVC core

I try to add a custom attribute to validate required field and trim value for white space.
So here is my custom attribute :
[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = false)]
public class CustomRequired : ValidationAttribute, IClientModelValidator
{
public CustomRequired()
{
ErrorMessage = new ResourceManager(typeof(ErrorResource)).GetString("All_Required");
}
public void AddValidation(ClientModelValidationContext context)
{
if (context == null)
throw new ArgumentNullException(nameof(context));
MergeAttribute(context.Attributes, "data-val", "true");
MergeAttribute(context.Attributes, "data-val-customrequired", ErrorMessage);
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
return value.ToString().Trim().Length > 0 ? ValidationResult.Success : new ValidationResult(ErrorMessage);
}
private static bool MergeAttribute(IDictionary<string, string> attributes, string key, string value)
{
if (attributes.ContainsKey(key))
{
return false;
}
attributes.Add(key, value);
return true;
}
}
And here how I add it (or try) :
$(document).ready(function () {
$.validator.addMethod("customrequired", function (value, element, parameters) {
return $.trim(value).length > 0;
});
$.validator.unobtrusive.adapters.addBool('customrequired');
});
And set it on property in a viewmodel :
[CustomRequired]
public string Code { get; set; }
My problem is it doesn't had any client side validation whereas the function is in the jQuery validator... The ModelState is invalid so the controller reject it but I want a client side validation.
console:
Edit :
I forgot to say I'm using kendo... See my own answer below.
I forgot to say that I'm using kendo...
My code is functional with a classic validation but not with kendo edit pop-up. :/
So here is the solution for those who have the same problem, write this in your javascript instead of add it in the $.validator :
(function ($, kendo) {
$.extend(true, kendo.ui.validator, {
rules: {
customrequired: function (input) {
if (input.is("[data-val-customrequired]")) {
return $.trim(input.val()).length > 0;
}
return true;
}
},
messages: {
customrequired: function (input) {
return input.attr("data-val-customrequired");
}
}
});
})(jQuery, kendo);

Data annotations, unobtrusive validation. Min age, max age

What do I want to achieve:
To show a seperate validation message for failing minimum age check and one for maximum age check
To store the minimum and maximum age in one area as integers. Not in js/ validator... only in the model. which I hope to change to look at a config file.
For the validation to work with jquery unobtrusive and server side, and to be in one place against the model (and obv some jquery)
To be enabled using data annotations
I wanted to check against DOB as a datetime, not have the user put in there age as an int. If i did I could have used [Min] notation and [Max] notation for age. It wasn't good enough.
Why didn't I use a range notation. I wanted to fire a different validation message for each min fail and max fail. I looked into this and had no look. I'd also have to pass in the range as a datetime and its static or something so I couldn't have done DateTime.Now.AddYears(-90) for instance.
My problems
I'm a noob at MVC, JQuery validation and the whole MVC architecture!
What I've come up with works. However, as you can see there is alot repeated code, I'd like to conform to DRY.
My first hack was to pass in the value that i'm checking against into the validation message. I got around this by doing...
[MaximumAgeCheck(90,"You have to be at most {0} to apply")]
and inside the validation attribute
private readonly int _min;
private readonly string _defaultErrorMessage = "";
public MinimumAgeCheck(int min, string defaultErrorMessage)
: base(defaultErrorMessage)
{
_min = min;
_defaultErrorMessage = defaultErrorMessage.Replace("{0}", _min.ToString());
}
and I used it for instance like so..
return new ValidationResult(_defaultErrorMessage);
I know this isn't the right way to do it, and wondered what is the best way to do this?
Second hack!
I'm passing in two validation parameters which I want to be able to access in the jQuery.validator.addMethod... method.
I tried to access these parameters by doing the following... params.[thevalueiadded], params[0]... etc, I even logged out params into console.log but it never showed me all the params, only the first value as a string!
My work around was to store the javascript variables at the top and load them from the adapters.add.
I'm probabily making little sense so here is the code, that works...I warn you, it is messy!
Model property and data annotation
[Required(ErrorMessage = "Date of birth required")]
[Display(Name = "Date of Birth")]
[DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}")]
[DataType(DataType.DateTime, ErrorMessage = "Date of birth should be in dd/mm/yyyy format")]
[MinimumAgeCheck(18,"You have to be at least {0} to apply")]
[MaximumAgeCheck(90,"You have to be at most {0} to apply")]
public DateTime? DateOfBirth { get; set; }
Minimum Age Check and Maximum age check
validation attributes
public class MinimumAgeCheck : ValidationAttribute, IClientValidatable
{
private readonly int _min;
private readonly string _defaultErrorMessage = "";
public MinimumAgeCheck(int min, string defaultErrorMessage)
: base(defaultErrorMessage)
{
_min = min;
_defaultErrorMessage = defaultErrorMessage.Replace("{0}", _min.ToString());
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
DateTime dtV = (DateTime)value;
long lTicks = DateTime.Now.Ticks - dtV.Ticks;
DateTime dtAge = new DateTime(lTicks);
if (!(dtAge.Year >= _min && dtAge.Year <= 30))
{
return new ValidationResult(_defaultErrorMessage);
}
return ValidationResult.Success;
}
public override string FormatErrorMessage(string name)
{
return String.Format(CultureInfo.CurrentUICulture, ErrorMessageString, _min);
}
public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
{
ModelClientValidationRule mcvrTwo = new ModelClientValidationRule();
mcvrTwo.ValidationType = "checkminimumage";
mcvrTwo.ErrorMessage = _defaultErrorMessage;
mcvrTwo.ValidationParameters.Add("todaysdate", DateTime.Now.ToString("dd/MM/yyyy"));
mcvrTwo.ValidationParameters.Add("lowerage", _min.ToString());
return new List<ModelClientValidationRule> { mcvrTwo };
}
}
public class MaximumAgeCheck : ValidationAttribute, IClientValidatable
{
private readonly int Max;
private readonly string _defaultErrorMessage = "";
public MaximumAgeCheck(int max, string defaultErrorMessage)
: base(defaultErrorMessage)
{
Max = max;
_defaultErrorMessage = defaultErrorMessage.Replace("{0}", Max.ToString());
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
DateTime dtV = (DateTime)value;
long lTicks = DateTime.Now.Ticks - dtV.Ticks;
DateTime dtAge = new DateTime(lTicks);
if (!(dtAge.Year >= Max && dtAge.Year <= 30))
{
return new ValidationResult(_defaultErrorMessage);
}
return ValidationResult.Success;
}
public override string FormatErrorMessage(string name)
{
return String.Format(CultureInfo.CurrentUICulture, ErrorMessageString,Max);
}
public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
{
ModelClientValidationRule mcvrTwo = new ModelClientValidationRule();
mcvrTwo.ValidationType = "checkmaximumage";
mcvrTwo.ErrorMessage = _defaultErrorMessage;
mcvrTwo.ValidationParameters.Add("todaysdate", DateTime.Now.ToString("dd/MM/yyyy"));
mcvrTwo.ValidationParameters.Add("upperage", Max.ToString());
return new List<ModelClientValidationRule> { mcvrTwo };
}
}
The Jquery
(function ($) {
var mintodaysDateVal;
var maxtodaysDateVal;
var lowerageVal;
var upperageVal;
jQuery.validator.unobtrusive.adapters.add("checkminimumage", ['lowerage', 'todaysdate', 'upperage'], function (options) {
options.rules["checkminimumage"] = options.params;
mintodaysDateVal = options.params.todaysdate;
lowerageVal = options.params.lowerage;
options.messages["checkminimumage"] = options.message;
});
jQuery.validator.addMethod("checkminimumage", function (value, element, params) {
var currDate = mintodaysDateVal;
var sdoc = currDate.split('/');
var dobDate = value;
var sdob = dobDate.split('/');
//pass year,month,date in new Date object.
var vDOB = new Date(sdob[2], sdob[1] - 1, sdob[0]);
var vDOC = new Date(sdoc[2], sdoc[1] - 1, sdoc[0]);
//getAge user define function to calculate age.
var vYrs = getAge(vDOB, vDOC);
var result = false;
if (vYrs >= lowerageVal) { result = true; }
return result;
});
jQuery.validator.unobtrusive.adapters.add("checkmaximumage", ['lowerage', 'todaysdate', 'upperage'], function (options) {
options.rules["checkmaximumage"] = options.params;
maxtodaysDateVal = options.params.todaysdate;
upperageVal = options.params.upperage;
options.messages["checkmaximumage"] = options.message;
});
jQuery.validator.addMethod("checkmaximumage", function (value, element, params) {
var currDate = maxtodaysDateVal;
var sdoc = currDate.split('/');
var dobDate = value;
var sdob = dobDate.split('/');
var vDOB = new Date(sdob[2], sdob[1] - 1, sdob[0]);
var vDOC = new Date(sdoc[2], sdoc[1] - 1, sdoc[0]);
var vYrs = getAge(vDOB, vDOC);
var result = false;
if (vYrs <= upperageVal) { result = true; }
return result;
});
function getAge(oldDate, currDate) {
return currDate.getFullYear() - oldDate.getFullYear();
}
} (jQuery));
I hope this makes sense, I've read it over and its quite garbled... so i'll be happy to answer any comments.
Really useful code, but the ValidationResult IsValid method has some bugs. It doesn't handle future dates or blank dates. Plus it seems to have a hard coded limit to age 30 in - looks to be debug code? Anyway, I addressed those issues for my code and came up with the below:
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
if (value == null)
{
return new ValidationResult(_defaultErrorMessage);
}
DateTime dtV = (DateTime)value;
long lTicks = DateTime.Now.Ticks - dtV.Ticks;
if (lTicks < 0)
{
return new ValidationResult(_defaultErrorMessage);
}
DateTime dtAge = new DateTime(lTicks);
if (!(dtAge.Year >= _min ))
{
return new ValidationResult(_defaultErrorMessage);
}
return ValidationResult.Success;
}
Take a look at the MVC Foolproof Validation library. You can find it in NuGet.
It has pretty much all the validation you need and is added via data annotations. It will intergrate nicely into the unobtrusive client side validation.

MVC3 Client Validation JS formatted Error Message Automatically?

I created a custom validation with following sample JS code:
(function ($) {
$.validator.unobtrusive.adapters.add('myrule', ['minvalueproperty', 'maxvalueproperty'],
function (options) {
options.rules['myrule'] = options.params;
options.messages['currencyrule'] = options.message;
}
);
$.validator.addMethod('myrule', function (value, element, params) {
return false;
}
} (jQuery));
Server side validator code is
[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
public class MyValidationAttribute : ValidationAttribute, IClientValidatable
{
public CurrencyValidationAttribute(string minPropertyName, string maxPropertyName)
: base (DefaultErrorMessage)
{
this.minPropertyName = minPropertyName;
this.maxPropertyName = maxPropertyName;
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
return new ValidationResult(this.ErrorMessage);
}
public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
{
var clientValidationRule = new ModelClientValidationRule
{
ValidationType = "myrule",
ErrorMessage = this.ErrorMessage,
};
clientValidationRule.ValidationParameters["minvalueproperty"] = minPropertyName;
clientValidationRule.ValidationParameters["maxvalueproperty"] = maxPropertyName;
yield return clientValidationRule;
}
}
My model class is decorated with my custom validation attribute
[MyValidation("MinValue", "MaxValue",
ErrorMessage = "Wrong value, must be between {0} and {1}")]
public string Money { get; set; }
It appears to work for most part other than error message displaying. In my model property I have used a string with place holders to be replaced, but there is no actual code yet.
When I run the page, I entered some invalid value to the text box and forced client side validation to return false, the funny thing is that the error message I saw was
Wrong value, must be between [object Object] and {1}
Somehow {0} was replaced automatically. Any clue what is the reason the error message got replaced?

How to validate one field related to another's value in ASP .NET MVC 3

I had two fields some thing like phone number and mobile number. Some thing like..
[Required]
public string Phone { get; set; }
[Required]
public string Mobile{ get; set; }
But user can enter data in either one of it. One is mandatory. How to handle them i.e how to disable the required field validator for one field when user enter data in another field and viceversa. In which event i have to handle it in javascript and what are the scripts i need to add for this. Can anyone please help to find the solution...
One possibility is to write a custom validation attribute:
public class RequiredIfOtherFieldIsNullAttribute : ValidationAttribute, IClientValidatable
{
private readonly string _otherProperty;
public RequiredIfOtherFieldIsNullAttribute(string otherProperty)
{
_otherProperty = otherProperty;
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
var property = validationContext.ObjectType.GetProperty(_otherProperty);
if (property == null)
{
return new ValidationResult(string.Format(
CultureInfo.CurrentCulture,
"Unknown property {0}",
new[] { _otherProperty }
));
}
var otherPropertyValue = property.GetValue(validationContext.ObjectInstance, null);
if (otherPropertyValue == null || otherPropertyValue as string == string.Empty)
{
if (value == null || value as string == string.Empty)
{
return new ValidationResult(string.Format(
CultureInfo.CurrentCulture,
FormatErrorMessage(validationContext.DisplayName),
new[] { _otherProperty }
));
}
}
return null;
}
public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
{
var rule = new ModelClientValidationRule
{
ErrorMessage = FormatErrorMessage(metadata.GetDisplayName()),
ValidationType = "requiredif",
};
rule.ValidationParameters.Add("other", _otherProperty);
yield return rule;
}
}
which you would apply to one of the properties of your view model:
public class MyViewModel
{
[RequiredIfOtherFieldIsNull("Mobile")]
public string Phone { get; set; }
public string Mobile { get; set; }
}
then you could have a controller:
public class HomeController : Controller
{
public ActionResult Index()
{
return View(new MyViewModel());
}
[HttpPost]
public ActionResult Index(MyViewModel model)
{
return View(model);
}
}
and finally a view in which you will register an adapter to wire the client side validation for this custom rule:
#model MyViewModel
<script src="#Url.Content("~/Scripts/jquery.validate.js")" type="text/javascript"></script>
<script src="#Url.Content("~/Scripts/jquery.validate.unobtrusive.js")" type="text/javascript"></script>
<script type="text/javascript">
jQuery.validator.unobtrusive.adapters.add(
'requiredif', ['other'], function (options) {
var getModelPrefix = function (fieldName) {
return fieldName.substr(0, fieldName.lastIndexOf('.') + 1);
}
var appendModelPrefix = function (value, prefix) {
if (value.indexOf('*.') === 0) {
value = value.replace('*.', prefix);
}
return value;
}
var prefix = getModelPrefix(options.element.name),
other = options.params.other,
fullOtherName = appendModelPrefix(other, prefix),
element = $(options.form).find(':input[name="' + fullOtherName + '"]')[0];
options.rules['requiredif'] = element;
if (options.message) {
options.messages['requiredif'] = options.message;
}
}
);
jQuery.validator.addMethod('requiredif', function (value, element, params) {
var otherValue = $(params).val();
if (otherValue != null && otherValue != '') {
return true;
}
return value != null && value != '';
}, '');
</script>
#using (Html.BeginForm())
{
<div>
#Html.LabelFor(x => x.Phone)
#Html.EditorFor(x => x.Phone)
#Html.ValidationMessageFor(x => x.Phone)
</div>
<div>
#Html.LabelFor(x => x.Mobile)
#Html.EditorFor(x => x.Mobile)
#Html.ValidationMessageFor(x => x.Mobile)
</div>
<button type="submit">OK</button>
}
Pretty sick stuff for something so extremely easy as validation rule that we encounter in our everyday lives. I don't know what the designers of ASP.NET MVC have been thinking when they decided to pick a declarative approach for validation instead of imperative.
Anyway, that's why I use FluentValidation.NET instead of data annotations to perform validations on my models. Implementing such simple validation scenarios is implemented in a way that it should be - simple.
I know this question is not so hot, because it was asked relatively long time ago, nevertheless I'm going to share with a slightly different idea of solving such an issue. I decided to implement mechanism which provides conditional attributes to calculate validation results based on other properties values and relations between them, which are defined in logical expressions.
Your problem can be defined and automatically solved by the usage of following annotations:
[RequiredIf("Mobile == null",
ErrorMessage = "At least email or phone should be provided.")]
public string Phone{ get; set; }
[RequiredIf("Phone == null",
ErrorMessage = "At least email or phone should be provided.")]
public string Mobile { get; set; }
If you feel it would be useful for your purposes, more information about ExpressiveAnnotations library can be found here. Client side validation is also supported out of the box.
Since nobody else suggested it, I'm going to tell you a different way to do this that we use.
If you create a notmapped field of a custom data type (in my example, a pair of gps points), you can put the validator on that and you don't even need to use reflection to get all the values.
[NotMapped]
[DCGps]
public GPS EntryPoint
{
get
{
return new GPS(EntryPointLat, EntryPointLon);
}
}
and the class, a standard getter/setter
public class GPS
{
public decimal? lat { get; set; }
public decimal? lon { get; set; }
public GPS(decimal? lat, decimal? lon)
{
this.lat = lat;
this.lon = lon;
}
}
and now the validator:
public class DCGps : DCValidationAttribute
{
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
if (!(value is GPS)) {
return new ValidationResult("DCGps: This annotation only works with fields with the data type GPS.");
}
//value stored in the field.
//these come through as zero or emptry string. Normalize to ""
string lonValue = ((GPS)value).lonstring == "0" ? "" : ((GPS)value).lonstring;
string latValue = ((GPS)value).latstring == "0" ? "" : ((GPS)value).latstring;
//place validation code here. You have access to both values.
//If you have a ton of values to validate, you can do them all at once this way.
}
}

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