For a project at work I'm trying to create a process that lets a user dynamically create a form that other users could then fill out the values for. I'm having trouble figuring out how to go about getting this to play nice with the built in model binding and validation with ASP MVC 3, though.
Our view model is set up something like this. Please note that I've over simplified the example code:
public class Form
{
public FieldValue[] FieldValues { get; set; }
}
public class Field
{
public bool IsRequired { get; set; }
}
public class FieldValue
{
public Field Field { get; set; }
public string Value { get; set; }
}
And our view looks something like:
#model Form
#using (Html.BeginForm("Create", "Form", FormMethod.Post))
{
#for(var i = 0; i < Model.Fields.Count(); i++)
{
#Html.TextBoxFor(_ => #Model.Fields[i].Value)
}
<input type="submit" value="Save" name="Submit" />
}
I was hoping that we'd be able to create a custom ModelValidatorProvider or ModelMetadataProvider class that would be able to analyze a FieldValue instance, determine if its Field.IsRequired property is true, and then add a RequiredFieldValidator to that specific instance's validators. I'm having no luck with this, though. It seems that with ModelValidatorProvider(and ModelMetadataProvider) you can't access the parent container's value(ie: GetValidators() will be called for FieldValue.Value, but there's no way from there to get the FieldValue object).
Things I've tried:
In the ModelValidatorProvider, I've tried using
ControllerContext.Controller.ViewData.Model, but that doesn't work if
you have nested types. If I'm trying to figure out the validators
Form.FieldValues[3], I have no idea which FieldValue to use.
I tried using a custom ModelMetadata that tries to use the internal
modelAccessor's Target property to get the parent, but this also
doesn't work if you have a nested type. Somewhere internal to MVC, an
expression like the one in my example will result in the Target being
the Model's type(Form), not FieldValue. So I get the same problem as
above where I have no idea what instance of FieldValue to compare
against.
A class-level validation attribute that I could put on the FieldValue
class itself, but this only gets called during server validation. I
need client-side validation, too.
Is what I'm trying to do even possible in MVC? Or is there something I'm missing entirely?
One possibility is to use a custom validation attribute.
But before getting into the implementation I would like to point out a potential flaw in your scenario. The IsRequired property is part of your model. This means that when the form is submitted its value must be known so that we conditionally apply the required rule to the corresponding property. But for this value to be known when the form is submitted this means that it must be either part of the form (as a hidden or standard input field) or must be retrieved from somewhere (datastore, ...). The problem with the first approach is obvious => hidden field means that the user can set whatever value he likes, so it's no longer a real validation because it is the user that decides which field is required.
This warning being said, let's suppose that you trust your users and decide to take the hidden field approach for storing the IsRequired value. Let's see how a sample implementation:
Model:
public class Form
{
public FieldValue[] Fields { get; set; }
}
public class FieldValue
{
public Field Field { get; set; }
[ConditionalRequired("Field")]
public string Value { get; set; }
}
public class Field
{
public bool IsRequired { get; set; }
}
Controller:
public class HomeController : Controller
{
public ActionResult Index()
{
var model = new Form
{
Fields = new[]
{
new FieldValue { Field = new Field { IsRequired = true }, Value = "" },
new FieldValue { Field = new Field { IsRequired = true }, Value = "" },
new FieldValue { Field = new Field { IsRequired = false }, Value = "value 3" },
}
};
return View(model);
}
[HttpPost]
public ActionResult Index(Form model)
{
return View(model);
}
}
View:
#model Form
#using (Html.BeginForm())
{
#Html.EditorFor(x => x.Fields)
<input type="submit" value="Save" name="Submit" />
}
ConditionalRequiredAttribute:
public class ConditionalRequiredAttribute : ValidationAttribute, IClientValidatable
{
private RequiredAttribute _innerAttribute = new RequiredAttribute();
private readonly string _fieldProperty;
public ConditionalRequiredAttribute(string fieldProperty)
{
_fieldProperty = fieldProperty;
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
var containerType = validationContext.ObjectInstance.GetType();
var field = containerType.GetProperty(_fieldProperty);
if (field == null)
{
return new ValidationResult(string.Format("Unknown property {0}", _fieldProperty));
}
var fieldValue = (Field)field.GetValue(validationContext.ObjectInstance, null);
if (fieldValue == null)
{
return new ValidationResult(string.Format("The property {0} was null", _fieldProperty));
}
if (fieldValue.IsRequired && !_innerAttribute.IsValid(value))
{
return new ValidationResult(this.ErrorMessage, new[] { validationContext.MemberName });
}
return ValidationResult.Success;
}
public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
{
var rule = new ModelClientValidationRule()
{
ErrorMessage = FormatErrorMessage(metadata.GetDisplayName()),
ValidationType = "conditionalrequired",
};
rule.ValidationParameters.Add("iserquiredproperty", _fieldProperty + ".IsRequired");
yield return rule;
}
}
Associated unobtrusive adapter:
(function ($) {
$.validator.unobtrusive.adapters.add('conditionalrequired', ['iserquiredproperty'], function (options) {
options.rules['conditionalrequired'] = options.params;
if (options.message) {
options.messages['conditionalrequired'] = options.message;
}
});
$.validator.addMethod('conditionalrequired', function (value, element, parameters) {
var name = $(element).attr('name'),
prefix = name.substr(0, name.lastIndexOf('.') + 1),
isRequiredFiledName = prefix + parameters.iserquiredproperty,
requiredElement = $(':hidden[name="' + isRequiredFiledName + '"]'),
isRequired = requiredElement.val().toLowerCase() === 'true';
if (!isRequired) {
return true;
}
return value && value !== '';
});
})(jQuery);
Related
Let's assume that I have a view model like this
public class ExampleVM
{
[Display(Name = "Foo")]
public Nullable<decimal> FooInternal { get; set; }
}
My view looks like this (also a form tag which I omitted in this post)
#model ExampleVM
....
<input asp-for="FooInternal" class="form-control" type="number" />
This results in a rendered text box with FooInternal as id-attribute.
In my scenario, I also have a modal dialog with another form with another view model which shares a property with the same name. I know that the asp-for taghelper renders the id-attribute either a manually from a specified id or infers the id from the property name.
In my backend code, I want to be able to name my properties how I seem fit given the view model context. I don't want to rename my properties to make them globally unique.
I try to avoid two things:
To manually specify the id in the view / the input element. I'd much rather use an autogenerated id that I can set via another attribute in the backend.
Given that I use the view model with [FromBody] in a post, I can't exactly rename the property as it would be with [FromRoute(Name="MyFoo")]. I don't want to map a manually entered id back to my property.
Basically, I'm looking for something like this:
public class ExampleVM
{
[Display(Name = "Foo")]
[HtmlId(Name = "MyUniqueFooName")]
public Nullable<decimal> FooInternal { get; set; }
}
where HtmlId would be an attribute that interacts with the tag-helper for rendering and also for rebinding the view model as parameter from a [HttpPost] method.
Maybe another approach is also valid since avoiding multiple input elements (with the same identifier) in multiple forms on the same page seems like a common situation to me.
According to your description, if you want to achieve your requirement, you should write custom modelbinding and custom input tag helper to achieve your requirement.
Since the asp.net core modelbinding will bind the data according to the post back's form data, you should firstly write the custom input tag helper to render the input name property to use HtmlId value.
Then you should write a custom model binding in your project to bind the model according to the HtmlId attribute.
About how to re-write the custom input tag helper, you could refer to below steps:
Notice: Since the input tag helper has multiple type "file, radio,checkbox and else", you should write all the logic based on the source codes.
According to the input taghelper source codes, you could find the tag helper will call the Generator.GenerateTextBox method to generate the input tag html content.
The Generator.GenerateTextBox has five parameters, the third parameter expression is used to generate the input textbox's for attribute.
Generator.GenerateTextBox(
ViewContext,
modelExplorer,
For.Name,
modelExplorer.Model,
format,
htmlAttributes);
If you want to show the HtmlId value as the name for the for attribute, you should create a custom input taghelper.
You should firstly create a custom attribute:
[System.AttributeUsage(AttributeTargets.All, Inherited = false, AllowMultiple = true)]
public class HtmlId : Attribute
{
public string _Id;
public HtmlId(string Id) {
_Id = Id;
}
public string Id
{
get { return _Id; }
}
}
Then you could use var re = ((Microsoft.AspNetCore.Mvc.ModelBinding.Metadata.DefaultModelMetadata)For.ModelExplorer.Metadata).Attributes.PropertyAttributes.Where(x => x.GetType() == typeof(HtmlId)).FirstOrDefault(); to get the htmlid in the input tag helper's GenerateTextBox method.
Details, you could refer to below custom input tag helper codes:
using Microsoft.AspNetCore.Mvc.TagHelpers;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Razor.TagHelpers;
using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.AspNetCore.Mvc.Rendering;
namespace SecurityRelatedIssue
{
[HtmlTargetElement("input", Attributes = ForAttributeName, TagStructure = TagStructure.WithoutEndTag)]
public class CustomInputTagHelper: InputTagHelper
{
private const string ForAttributeName = "asp-for";
private const string FormatAttributeName = "asp-format";
public override int Order => -10000;
public CustomInputTagHelper(IHtmlGenerator generator)
: base(generator)
{
}
public override void Process(TagHelperContext context, TagHelperOutput output)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (output == null)
{
throw new ArgumentNullException(nameof(output));
}
// Pass through attributes that are also well-known HTML attributes. Must be done prior to any copying
// from a TagBuilder.
if (InputTypeName != null)
{
output.CopyHtmlAttribute("type", context);
}
if (Name != null)
{
output.CopyHtmlAttribute(nameof(Name), context);
}
if (Value != null)
{
output.CopyHtmlAttribute(nameof(Value), context);
}
// Note null or empty For.Name is allowed because TemplateInfo.HtmlFieldPrefix may be sufficient.
// IHtmlGenerator will enforce name requirements.
var metadata = For.Metadata;
var modelExplorer = For.ModelExplorer;
if (metadata == null)
{
throw new InvalidOperationException();
}
string inputType;
string inputTypeHint;
if (string.IsNullOrEmpty(InputTypeName))
{
// Note GetInputType never returns null.
inputType = GetInputType(modelExplorer, out inputTypeHint);
}
else
{
inputType = InputTypeName.ToLowerInvariant();
inputTypeHint = null;
}
// inputType may be more specific than default the generator chooses below.
if (!output.Attributes.ContainsName("type"))
{
output.Attributes.SetAttribute("type", inputType);
}
// Ensure Generator does not throw due to empty "fullName" if user provided a name attribute.
IDictionary<string, object> htmlAttributes = null;
if (string.IsNullOrEmpty(For.Name) &&
string.IsNullOrEmpty(ViewContext.ViewData.TemplateInfo.HtmlFieldPrefix) &&
!string.IsNullOrEmpty(Name))
{
htmlAttributes = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase)
{
{ "name", Name },
};
}
TagBuilder tagBuilder;
switch (inputType)
{
//case "hidden":
// tagBuilder = GenerateHidden(modelExplorer, htmlAttributes);
// break;
//case "checkbox":
// tagBuilder = GenerateCheckBox(modelExplorer, output, htmlAttributes);
// break;
//case "password":
// tagBuilder = Generator.GeneratePassword(
// ViewContext,
// modelExplorer,
// For.Name,
// value: null,
// htmlAttributes: htmlAttributes);
// break;
//case "radio":
// tagBuilder = GenerateRadio(modelExplorer, htmlAttributes);
// break;
default:
tagBuilder = GenerateTextBox(modelExplorer, inputTypeHint, inputType, htmlAttributes);
break;
}
if (tagBuilder != null)
{
// This TagBuilder contains the one <input/> element of interest.
output.MergeAttributes(tagBuilder);
if (tagBuilder.HasInnerHtml)
{
// Since this is not the "checkbox" special-case, no guarantee that output is a self-closing
// element. A later tag helper targeting this element may change output.TagMode.
output.Content.AppendHtml(tagBuilder.InnerHtml);
}
}
}
private TagBuilder GenerateTextBox(
ModelExplorer modelExplorer,
string inputTypeHint,
string inputType,
IDictionary<string, object> htmlAttributes)
{
var format = Format;
if (string.IsNullOrEmpty(format))
{
if (!modelExplorer.Metadata.HasNonDefaultEditFormat &&
string.Equals("week", inputType, StringComparison.OrdinalIgnoreCase) &&
(modelExplorer.Model is DateTime || modelExplorer.Model is DateTimeOffset))
{
// modelExplorer = modelExplorer.GetExplorerForModel(FormatWeekHelper.GetFormattedWeek(modelExplorer));
}
else
{
//format = GetFormat(modelExplorer, inputTypeHint, inputType);
}
}
if (htmlAttributes == null)
{
htmlAttributes = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
}
htmlAttributes["type"] = inputType;
if (string.Equals(inputType, "file"))
{
htmlAttributes["multiple"] = "multiple";
}
var re = ((Microsoft.AspNetCore.Mvc.ModelBinding.Metadata.DefaultModelMetadata)For.ModelExplorer.Metadata).Attributes.PropertyAttributes.Where(x => x.GetType() == typeof(HtmlId)).FirstOrDefault();
return Generator.GenerateTextBox(
ViewContext,
modelExplorer,
((HtmlId)re).Id,
modelExplorer.Model,
format,
htmlAttributes);
}
}
}
Improt this taghelper in _ViewImports.cshtml
#addTagHelper *,[yournamespace]
Model exmaple:
[Display(Name = "Foo")]
[HtmlId("test")]
public string str { get; set; }
Result:
Then you could write a custom model binding for the model to bind the data according to the htmlid. About how to use custom model binding, you could refer to this article.
I am currently developing a Framework to generate dynamic Views in MVC, the idea is based on this tutorial.
The next step is adding the possibility to generate multiple submit buttons but I cant get it to work. I did some research and found this approach. However, since i want to generate those buttons dynamically, this does not work yet.
What I tried is to modify this attribute code here:
[AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public class MultipleButtonAttribute : ActionNameSelectorAttribute
{
public string Name { get; set; }
public string Argument { get; set; }
public override bool IsValidName(ControllerContext controllerContext, string actionName, MethodInfo methodInfo)
{
var isValidName = false;
var keyValue = string.Format("{0}:{1}", Name, Argument);
var value = controllerContext.Controller.ValueProvider.GetValue(keyValue);
if (value != null)
{
controllerContext.Controller.ControllerContext.RouteData.Values[Name] = Argument;
isValidName = true;
}
return isValidName;
}
}
While debugging I digged down the ValueProvider and found out that the JQueryFormValueProvider in the Collection of Valueproviders actually contains the Name of the clicked submitbutton.
The button is generated like this:
<input type="submit" name="buttonClick:#Model.Id" value="#Model.Text" />
Unfortunately the ValueProviders do not let me Iterate through the Keys so I dont know how to get the value I circled red in the above screenshot.
It doesnt need to be this approach, all what counts is, to find out which button was clicked.
Ok i found the solution by modifying the Attribute-code like this:
[AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public class NameToRouteDataAttribute : ActionNameSelectorAttribute
{
/// <Summary>Name of the Value you want to grab from the control.</Summary>
public string Name { get; set; }
public override bool IsValidName(ControllerContext controllerContext, string actionName, MethodInfo methodInfo)
{
ValueProviderCollection providers = controllerContext.Controller.ValueProvider as ValueProviderCollection;
if (providers != null)
{
// We need this value-Provider as it contains the Data from the Form
JQueryFormValueProvider formProvider = providers.OfType<JQueryFormValueProvider>().FirstOrDefault();
if (formProvider != null)
{
// now look for the specified value-prefix.
var kvp = formProvider.GetKeysFromPrefix(Name).FirstOrDefault();
if (kvp.Key != null)
controllerContext.Controller.ControllerContext.RouteData.Values[Name] = kvp.Key;
}
}
return true;
}
}
Contollercode:
[HttpPost]
[NameToRouteDataAttribute(Name = "buttonClick")]
public ActionResult Show(FormViewModel form)
{
string buttonId = RouteData.GetRequiredString("buttonClick");
...
}
Buttoncode
#model MvcForms.Controls.ButtonViewModel
<input type="submit" name="buttonClick.#Model.Id" value="#Model.Text" />
The important thing here is, that the name of the Button contains a dot. This makes the JQueryFormValueProvider.GetKeysFromPrefix work the way I need it to.
I'm using Steve Sandersons BeginCollectionItem extension to help with binding lists of items. This works fine for primitive types. The problem I'm having is that for a custom model binder that I've written I can't see how to generate the full name and index of the item that I'm binding to.
Currently my model binder looks like this:
public class MoneyModelBinder : DefaultModelBinder
{
protected override void OnModelUpdated(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var valueResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName + ".Amount");
if (valueResult != null)
{
var value = valueResult.AttemptedValue;
var currencyCode = bindingContext.ValueProvider.GetValue(bindingContext.ModelName + ".Iso3LetterCode").AttemptedValue;
var money = (Money) bindingContext.Model;
Money parsedValue;
if (String.IsNullOrEmpty(value))
{
money.Amount = null;
return;
}
var currency = Currency.FromIso3LetterCode(currencyCode);
if (!Money.TryParse(value, currency, out parsedValue))
{
bindingContext.ModelState.AddModelError("Amount", string.Format("Unable to parse {0} as money", value));
}
else
{
money.Amount = parsedValue.Amount;
money.Currency = parsedValue.Currency;
}
}
else
{
base.OnModelUpdated(controllerContext, bindingContext);
}
}
}
My ViewModel Lokks like this (some propertis omitted for clarity):
public class EditFeeEarningCapacityViewModel
{
public List<FeeEarner> FeeEarners { get; set; }
public class FeeEarner
{
public Money AverageChargeOutRate { get; set; }
}
}
My Edit Template for the Money type looks like this:
#model Core.Money
#{
int decimalPlaces;
if(!int.TryParse(string.Format("{0}", ViewData["DecimalPlaces"]), out decimalPlaces))
{
decimalPlaces = 0;
}
}
<div class="input-prepend">
<span class="add-on">#Model.Currency.Symbol</span>#Html.TextBoxFor(m => m.Amount,
new
{
placeholder = string.Format("{0}", Model.Currency),
#class = "input-mini",
Value = String.Format("{0:n" + decimalPlaces + "}", Model.Amount)
})
</div>
#Html.HiddenFor(x => x.Iso3LetterCode)
For a form that has post values like this:
FeeEarners.index 3fa91d09-0617-4bea-ae3f-d84862be8c04
FeeEarners[3fa91d09-0617-4bea-ae3f-d84862be8c04].feeEarner.AverageChargeOutRate.Amount 500
FeeEarners[3fa91d09-0617-4bea-ae3f-d84862be8c04].feeEarner.AverageChargeOutRate.Iso3LetterCode GBP
I can't see how to detect the index of the item or the property name that I'm binding to. So essentially, how do I find the index of the item I'm trying to bind to and the name of the property that I'm trying to bind the data from?
I am not fimilar with that Helper but for collection i am doing a bit different trick.
define key
var key = "EditModel[{0}].{1}";
var index = 0;
then build form
foreach(var fee in Model.FeeEarners){
#Html.TextBox(string.Format(key, index, "PropertyNameFromYourFeeClass"));
//It will build text box and set value
}
On Controller side
create action with input parameter
public ActionResult Save(EditFeeEarningCapacityViewModel editModel){
...your code here
}
I have the following view models:
public class Search {
public int Id { get; set; }
[Required(ErrorMessage = "Please choose a name.")]
public string Name { get; set; }
[ValidGroup(ErrorMessage = "Please create a new group or choose an existing one.")]
public Group Group { get; set; }
}
public class Group {
public int Id { get; set; }
public string Name { get; set; }
}
I have defined a custom validation attribute as follows:
public class ValidGroupAttribute : ValidationAttribute {
public override bool IsValid(object value) {
if (value == null)
return false;
Group group = (Group)value;
return !(string.IsNullOrEmpty(group.Name) && group.Id == 0);
}
}
I have the following view (omitted some for brevity):
#Html.ValidationSummary()
<p>
<!-- These are custom HTML helper extensions. -->
#Html.RadioButtonForBool(m => m.NewGroup, true, "New", new { #class = "formRadioSearch", id = "NewGroup" })
#Html.RadioButtonForBool(m => m.NewGroup, false, "Existing", new { #class = "formRadioSearch", id = "ExistingGroup" })
</p>
<p>
<label>Group</label>
#if (Model.Group != null && Model.Group.Id == 0) {
#Html.TextBoxFor(m => m.Group.Name)
}
else {
#Html.DropDownListFor(m => m.Group.Id, Model.Groups)
}
</p>
The issue I'm having is the validation class input-validation-error does not get applied to the Group input. I assume this is because the framework is trying to find a field with id="Group" and the markup that is being generated has either id="Group_Id" or id=Group_Name. Is there a way I can get the class applied?
http://f.cl.ly/items/0Y3R0W3Z193s3d1h3518/Capture.PNG
Update
I've tried implementing IValidatableObject on the Group view model instead of using a validation attribute but I still can't get the CSS class to apply:
public class Group : IValidatableObject
{
public int Id { get; set; }
public string Name { get; set; }
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext) {
if (string.IsNullOrEmpty(Name) && Id == 0) {
yield return new ValidationResult("Please create a new group or select an existing one.", new[] { "Group.Name" });
}
}
}
Update 2
Self validation doesn't work. I think this is because the second parameter in the ValidationResult constructor isn't used in the MVC framework.
From: http://www.devtrends.co.uk/blog/the-complete-guide-to-validation-in-asp.net-mvc-3-part-2
In some situations, you might be tempted to use the second constructor overload of ValidationResult that takes in an IEnumerable of member names. For example, you may decide that you want to display the error message on both fields being compared, so you change the code to this:
return new ValidationResult(
FormatErrorMessage(validationContext.DisplayName), new[] { validationContext.MemberName, OtherProperty });
If you run your code, you will find absolutely no difference. This is because although this overload is present and presumably used elsewhere in the .NET framework, the MVC framework completely ignores ValidationResult.MemberNames.
I've come up with a solution that works but is clearly a work around.
I've removed the validation attribute and created a custom model binder instead which manually adds an error to the ModelState dictionary for the property Group.Name.
public class SearchBinder : DefaultModelBinder {
protected override void BindProperty(ControllerContext controllerContext, ModelBindingContext bindingContext,
PropertyDescriptor propertyDescriptor) {
if (propertyDescriptor.Name == "Group" &&
bindingContext.ValueProvider.GetValue("Group.Name") != null &&
bindingContext.ValueProvider.GetValue("Group.Name").AttemptedValue == "") {
ModelState modelState = new ModelState { Value = bindingContext.ValueProvider.GetValue("Group.Name") };
modelState.Errors.Add("Please create a new group or choose an existing one.");
bindingContext.ModelState.Add("Group.Name", modelState);
}
base.BindProperty(controllerContext, bindingContext, propertyDescriptor);
}
}
// Register custom model binders in Application_Start()
ModelBinders.Binders.Add(typeof(SearchViewModel), new SearchBinder());
With ModelState["Group.Name"] now having an error entry, the CSS class is being rendered in the markup.
I would much prefer if there was a way to do this with idiomatic validation in MVC though.
Solved!
Found a proper way to do this. I was specifying the wrong property name in the self validating class, so the key that was being added to the ModelState dictionary was Group.Group.Name. All I had to do was change the returned ValidationResult.
yield return new ValidationResult("Please create a new group or select an existing one.", new[] { "Name" });
Simple problem here (I think).
I have a form with a checkbox at the bottom where the user must agree to the terms and conditions. If the user doesn't check the box, I'd like an error message to be displayed in my validation summary along with the other form errors.
I added this to my view model:
[Required]
[Range(1, 1, ErrorMessage = "You must agree to the Terms and Conditions")]
public bool AgreeTerms { get; set; }
But that didn't work.
Is there an easy way to force a value to be true with data annotations?
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Threading.Tasks;
using System.Web.Mvc;
namespace Checked.Entitites
{
public class BooleanRequiredAttribute : ValidationAttribute, IClientValidatable
{
public override bool IsValid(object value)
{
return value != null && (bool)value == true;
}
public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
{
//return new ModelClientValidationRule[] { new ModelClientValidationRule() { ValidationType = "booleanrequired", ErrorMessage = this.ErrorMessage } };
yield return new ModelClientValidationRule()
{
ValidationType = "booleanrequired",
ErrorMessage = this.ErrorMessageString
};
}
}
}
There's actually a way to make it work with DataAnnotations. The following way:
[Required]
[Range(typeof(bool), "true", "true")]
public bool AcceptTerms { get; set; }
You can write a custom validation attribute which has already been mentioned. You will need to write custom javascript to enable the unobtrusive validation functionality to pick it up if you are doing client side validation. e.g. if you are using jQuery:
// extend jquery unobtrusive validation
(function ($) {
// add the validator for the boolean attribute
$.validator.addMethod(
"booleanrequired",
function (value, element, params) {
// value: the value entered into the input
// element: the element being validated
// params: the parameters specified in the unobtrusive adapter
// do your validation here an return true or false
});
// you then need to hook the custom validation attribute into the MS unobtrusive validators
$.validator.unobtrusive.adapters.add(
"booleanrequired", // adapter name
["booleanrequired"], // the names for the properties on the object that will be passed to the validator method
function(options) {
// set the properties for the validator method
options.rules["booleanRequired"] = options.params;
// set the message to output if validation fails
options.messages["booleanRequired] = options.message;
});
} (jQuery));
Another way (which is a bit of a hack and I don't like it) is to have a property on your model that is always set to true, then use the CompareAttribute to compare the value of your *AgreeTerms * attribute. Simple yes but I don't like it :)
ASP.Net Core 3.1
I know this is a very old question but for asp.net core the IClientValidatable does not exist and i wanted a solution that works with jQuery Unobtrusive Validation as well as on server validation so with the help of this SO question Link i made a small modification that works with boolean field like checkboxes.
Attribute Code
[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
public class MustBeTrueAttribute : ValidationAttribute, IClientModelValidator
{
public void AddValidation(ClientModelValidationContext context)
{
MergeAttribute(context.Attributes, "data-val", "true");
var errorMsg = FormatErrorMessage(context.ModelMetadata.GetDisplayName());
MergeAttribute(context.Attributes, "data-val-mustbetrue", errorMsg);
}
public override bool IsValid(object value)
{
return value != null && (bool)value == true;
}
private bool MergeAttribute(
IDictionary<string, string> attributes,
string key,
string value)
{
if (attributes.ContainsKey(key))
{
return false;
}
attributes.Add(key, value);
return true;
}
}
Model
[Display(Name = "Privacy policy")]
[MustBeTrue(ErrorMessage = "Please accept our privacy policy!")]
public bool PrivacyPolicy { get; set; }
Client Side Code
$.validator.addMethod("mustbetrue",
function (value, element, parameters) {
return element.checked;
});
$.validator.unobtrusive.adapters.add("mustbetrue", [], function (options) {
options.rules.mustbetrue = {};
options.messages["mustbetrue"] = options.message;
});