Currently I am trying to set dynamic the DisplayName of a property but I cannot find a way how get information of current property inside an attribute.
This is what I want to achieve:
Desired Outcome
My Attribute
public class DisplayNameFromPropertyAttribute : DisplayNameAttribute
{
public DisplayNameFromPropertyAttribute(string propertyName)
: base(GetDisplayName(propertyName))
{
}
private string GetDisplayBame(string propertyName)
{
// Get the value from the given property
}
}
My Model
I am trying to read the value from MyDisplayName into my custom DisplayNameFromProperty attribute
public class MyAwesomeModel
{
public string MyDisplayName { get; set; }
[Required]
[DisplayNameFromProperty("MyDisplayName")]
public string MyValue { get; set; }
}
My Page
#Html.LabelFor(model => model.MyValue)
#Html.TextBoxFor(model => model.MyValue)
#Html.ValidationMessageFor(model => model.MyValue)
Question
Currently I cannot find any reference on internet doing the same. Can someone help me out?
If this is not possible: What are the alternatives to achieve same result?
The ComponentModel.DataAnnotations validation attributes should use my custom display name
The #Html.LabelFor(model => model.MyValue) should use my custom display name
You can create a cusom HTML extension method that lets you do #Html.DictionaryLabelFor(x=>x.Property) and pull it from a dictionary
public static IHtmlString DictionaryLabelFor<TModel, TValue>(
this HtmlHelper<TModel> html,
Expression<Func<TModel, TValue>> expression, string text = null, string prefix = null)
{
var metadata = ModelMetadata.FromLambdaExpression(expression, html.ViewData);
var displayName = metadata.DisplayName;
if (string.IsNullOrWhiteSpace(text))
{
// Your code to get the label via reflection
// of the object
string labelText = "";
return html.Label(prefix + metadata.PropertyName, labelText);
}
else
{
return html.Label(prefix + metadata.PropertyName, text);
}
}
Overriding the properties on this works, only thing missing is the custom html attributes which wasn't needed when I wrote it
The validation error message is slightly different, you should always write custom errors for these fields so you can rely on them in a resx, you look at the modelstate for the (prefix + key) to get the errors, then get the translated value for each case.
You're best avoiding overwriting the standard HTML call as you'll be making excess calls where not needed elsewhere.
When you have that working and understand it the error messages section is pretty trivial to write in yourself, depends how you want to do the formatting on errors. I'm not writing it in as it's basically doing everything for you and if you don't understand how it works you'll be SOL when it comes to writing further extensions
Related
Let's say I have a test class like this:
public class TestClass
{
public Properties[] TestProperties { get; set; }
public Guid Id { get; set; }
public TestClass(Properties[] testProperties)
{
Id = Guid.NewGuid();
TestProperties = testProperties;
}
}
And a Properties class as follows:
public class Properties
{
public Guid Id { get; set; }
public string Name { get; set; }
public Properties(string name)
{
Name = name;
Id = Guid.NewGuid();
}
}
I need to validate that none of my properties Name at the TestProperties array is null, like this:
public class TestValidator : AbstractValidator<TestClass>
{
public TestValidator()
{
RuleForEach(x => x.TestProperties)
.Must(y => y.Name != string.Empty && y.Name != null)
.WithMessage("TestPropertie at {CollectionIndex}, can't be null or empty");
}
}
But instead of returning the position of the failing property, at the validation message, I would like to return it's Id, how can I do so?
Yes, using the default validators it's possible to inject other property values from the objects into the message.
This can be done by using the overload of WithMessage that takes a
lambda expression, and then passing the values to string.Format or by
using string interpolation.
Source
There are a couple of ways you can do it. Firstly, as per your current implementation using Must:
public class TestClassValidator : AbstractValidator<TestClass>
{
public TestClassValidator()
{
RuleForEach(x => x.TestProperties)
.Must(y => !string.IsNullOrEmpty(y.Name))
.WithMessage((testClass, testProperty) => $"TestProperty {testProperty.Id} name can't be null or empty");
}
}
I try to avoid using Must when possible, if you stick to using the built-in validators you stand a better chance of client-side validation working out of the box (if you're using it in a web app). Using ChildRules allows you to use the built-in validators and also get the benefit of using the fluent interface:
public class TestClassValidator : AbstractValidator<TestClass>
{
public TestClassValidator()
{
RuleForEach(x => x.TestProperties)
.ChildRules(testProperties =>
{
testProperties.RuleFor(testProperty => testProperty.Name)
.NotNull()
.NotEmpty()
.WithMessage(testProperty => $"TestProperty {testProperty.Id} name can't be null or empty");
});
}
}
ChildRules doco
I've included the NotNull() validator for verbosity/alignment with the custom error message, however it's not needed as NotEmpty() will cover the null or empty case.
Finally if it was me I'd probably create a separate validator for the Properties type (should this be Property?) and use SetValidator to include it. Splits up the validation concerns, defines the validation for a type once and makes the rules reusable, and makes the validators easier to test. I'm not going to cover that here as that feels beyond the scope of this question but the links below give examples on how to do it.
Child validator doco (SetValidator usage) here and here
Working samples of the above including tests can be found here.
I approached this a little differently, because I wanted a more reusable solution. (I'm validating many different classes in similar ways). Putting the message identification inside the extension with Must<> ties you to the type and could lead to copy&paste. Instead, I pass as an argument to the validation, a Func that returns an identifying string and lets the caller decide how to identify the object being validated.
public static IRuleBuilderOptions<T, string> IsValidStringEnumAllowNullable<T>(this IRuleBuilder<T, string> ruleBuilder, IList<string> validValues, Func<T,string> identifierLookup)
{
return ruleBuilder.Must((rootObject, testValue, context) =>
{
context.MessageFormatter.AppendArgument("AllowableValues", string.Join(", ", validValues));
context.MessageFormatter.AppendArgument("Identifier", identifierLookup(rootObject));
return string.IsNullOrEmpty(testValue) || validValues.Contains(testValue, StringComparer.Ordinal);
}).WithMessage("{Identifier}{PropertyName} with value {PropertyValue} must be one of the allowable values: {AllowableValues}, or null or empty string");
}
And then the calling code where I tell the specific validation message 'how' to identify the object for messaging:
base.RuleForEach(rq => rq.Thingies).ChildRules(x =>
{
x.RuleFor(f => f.MyProperty).IsValidStringEnumAllowNullable(ValidationStrings.AnArrayOfAllowedValues, f => $"Thing[{f.Id}] ");
});
The result of this code is
Thing[1234] My Property with value asdf must be one of the allowable values: Value1, ValidValue2, Somethingelse, or null or empty string
My model has an property whcih I assigned a ReadOnly tag. My intention is to set a propery to readonly true or false depending of a condition like
class Test {
static bool test() { // It is my model
// My logical response ...
return true;
}
[ReadOnly(test)]
datetime prop {get; set;}
}
using this model I get the error message:
Error 7 An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter
Could you, pleaee, get me an idea for this?
=====================================================================================
Solution like answer 3:
Inside Template:
cshtml:
...
#if (Model.condition) {
<td>#Html.EditorFor(m => m.prop)</td>
} else {
<td>#Html.DisplayFor(m => m.prop)</td>
}
...
It will be inside the template.
Inside Model in the copmnstructor I set the condition of the property condition:
class XX {
public condition { get; set; } // not necessary readonly, I do the logical inside the template.
public datetime prop {get; set; }
public XX (bool _condition) {
condition = _condition;
}
}
You cannot use something other than described in the error message as the parameter for attributes.
It is a sad true, but still a true.
Only this:
[ReadOnly(5)]
[ReadOnly("string")] // Or other type (int/long/byte/etc..) which can be used with const keyword.
[ReadOnly(Enums.SomeValue)]
[ReadOnly(typeof(SomeType))]
[ReadOnly(new string[] { "array", "of", "strings"} )]
So unfortunately, you wont succeed making custom parameter type:
class ReadOnlyAttribute { ReadOnlyAttribute(MyClass foo) { ... } }
One alternative would be to do it within the get/set, something like:
class test
{
static bool test() {
...
}
private datetime prop;
public datetime Prop
{
get { return prop; }
set
{
if (test)
prop = value;
else
// Ignore, throw exception, etc.
}
}
}
The metadata for the model (which includes your IsReadOnly) is created by the Model Metadata providers. This providers only have information about data types, and property names, but not about the concrete values of the properties of an instance of the model. So the metadata can not depend on the value of a property or method of the model class. (So implementing a Custom ModelMetada Provider wouldn't solve your problem).
Then, you have to find an alternative, hacky, way to do it:
Create a view model with two properties, the original, without the readonly attribute and an additional readonly property, decorated with the readonly attribute.
In the view, decide which of the two to show.
public class MyModel
{
public DateTime MyProperty { get; set;}
[ReadOnly]
public DateTime MyPropertyRo { get; set;}
}
If you want to recover the posted values, the editable version should use the original property in the Telerik control. The non-editable version should use the readonly property in the Telerik control, and the original property in a hidden-field, so that you can recover it in the post.
#if (Model.MyPropertyIsReadOnly)
{
#Html.HiddenFor(m => m.Property)
#Html.TelerikEditorFor(m => m.PropertyRo ...)
}
else
{
#Html.TelerikEditorFor(m => m.Property ...)
}
If you have to do this in many different views, you can create an Html helper (extension method for Html), which receives the 3 properties and includes the last sample code.
Finally, it would be even better to make a custom Editor template, but that's much harder to do if you don't have experience.
There is still another option: contact telerik, and ask them to implement a version of their control which receives a readonly parameter, and does this automatically for you. I think it must be really easy for them to implement it. So, if you're lucky enough...
I need to get the first initial of the first name
I have the following:
#Html.DisplayFor(modelItem => item.FirstName.Substring(1,1))
I get the following error though when the program tries to run it:
Templates can be used only with field access, property access, single-dimension array index, or single-parameter custom indexer expressions.
Simply add a property to your view model:
public string FirstName { get; set; }
public string FirstLetterOfName
{
get
{
// TODO: a minimum amount of error checking
// might be good here for cases when FirstName
// is null or an empty string
return this.FirstName.Substring(1, 1);
}
}
and then:
#Html.DisplayFor(modelItem => item.FirstLetterOfName)
And if you now tell me that you are not using view models but are directly passing your domain entities to your views (which is very bad design), you might use a custom template:
#Html.DisplayFor(modelItem => item.FirstName, "FirstLetter")
and then you define a custom display template ~/Views/Shared/DisplayTemplates/FirstLetter.cshtml with the following contents:
#ViewData.TemplateInfo.FormattedModelValue.Substring(1, 1)
You can't do this, because the mapping to your abject wont work like this. Like the exception message tells you you can only use it with properties.
You can however write your own HtmlHelper extension to do what you want
public static class HtmlHelpers
{
public static MvcHtmlString CustomDisplayFor(this HtmlHelper<Person> htmlHelper, Expression<Func<Person, string>> expression)
{
var customBuildString = string.Empty;
//Make your custom implementation here
return MvcHtmlString.Create(customBuildString);
}
}
Before substring, check the length of the string, else you will get index out of range exception;
#MvcHtmlString.Create(item.title.Length > 20 ? #item.title.ToString().Substring(0, 20):#item.title.ToString())
I'm using ASP.NET MVC3 with Razor and C#. I am making a form builder of sorts, so I have a model that has a collection of the following object:
public class MyFormField
{
public string Name { get; set; }
public string Value { get; set; }
public MyFormType Type { get; set; }
}
MyFormType is just an enum that tells me if the form field is a checkbox, or textbox, or file upload, or whatever. My editor template looks something like this (see the comment):
~/Views/EditorTemplates/MyFormField.cshtml
#model MyFormField
#{
switch (Model.Type)
{
case MyFormType.Textbox:
#Html.TextBoxFor(m => m.Value)
case MyFormType.Checkbox:
#Html.CheckBoxFor(m => m.Value) // This does not work!
}
}
I tried casting/converting the m.Value to a bool in the lambda expression for CheckBoxFor(), but that threw an error. I would just manually construct a checkbox input, but CheckBoxFor() seems to do two things that I can't seem to replicate:
Creates a hidden input that somehow gets populated by the checkbox. This appears to be what the model binder picks up.
Generates the name form the object so that the model binder gets the value into the right property.
Does anyone know a way around using CheckBoxFor() on a string, or a way to replicate its functionality manually, so that I can make this work?
You could also add a property on your viewmodel:
public class MyFormField
{
public string Name { get; set; }
public string Value { get; set; }
public bool CheckBoxValue
{
get { return Boolean.Parse(Value); }
}
public MyFormType Type { get; set; }
}
Your view would be something like this:
#model MyFormField
#{
switch (Model.Type)
{
case MyFormType.Textbox:
#Html.TextBoxFor(m => m.Value)
case MyFormType.Checkbox:
#Html.CheckBoxFor(m => m.CheckBoxValue) // This does work!
}
}
Use Boolean.TryParse if you want to avoid exceptions.
One way is to create your own htmlhelper extension method.
public static MvcHtmlString CheckBoxStringFor<TModel>(this HtmlHelper<TModel> html, Expression<Func<TModel, string>> expression)
{
// get the name of the property
string[] propertyNameParts = expression.Body.ToString().Split('.');
string propertyName = propertyNameParts.Last();
// get the value of the property
Func<TModel, string> compiled = expression.Compile();
string booleanStr = compiled(html.ViewData.Model);
// convert it to a boolean
bool isChecked = false;
Boolean.TryParse(booleanStr, out isChecked);
TagBuilder checkbox = new TagBuilder("input");
checkbox.MergeAttribute("id", propertyName);
checkbox.MergeAttribute("name", propertyName);
checkbox.MergeAttribute("type", "checkbox");
checkbox.MergeAttribute("value", "true");
if (isChecked)
checkbox.MergeAttribute("checked", "checked");
TagBuilder hidden = new TagBuilder("input");
hidden.MergeAttribute("name", propertyName);
hidden.MergeAttribute("type", "hidden");
hidden.MergeAttribute("value", "false");
return MvcHtmlString.Create(checkbox.ToString(TagRenderMode.SelfClosing) + hidden.ToString(TagRenderMode.SelfClosing));
}
The usage is the same as CheckBoxFor helper (e.Value is a string)
#Html.CheckBoxStringFor(e => e.Value)
Use the Checkbox, this simple way works fine
#Html.CheckBox("IsActive", Model.MyString == "Y" ? true : false)
I had this problem as well but was unable to modify the view model. Tried mdm20s solution but as i suspected it does not work on collection properties (it does not add the indexes to the names and ids like the native html helpers). To overcome this you can use the Html.CheckBox instead. It adds the proper indexes and you can pass the value of the checkbox yourself.
If you really want to use an expression you can always write a wrapper similar to mdm20s but replace everything after the TryParse with
return Html.CheckBox("propertyName", isChecked). Obviously you will need to add using System.Web.Mvc.Html as well.
I have created a custom ResourceProvider to pull localization information from a database. I now want to use DataAnnotation to add validation to the model.
DataAnnotation has ErrorMessageResourceType and ErrorMessageResourceName properties but ErrorMessageResourceType only accepts System.Type (i.e. a compiled resource file)
Is there any way to get DataAnnotation to use the custom ResourceProvider?
I realize this is an old question, but wanted to add a bit. I found myself in the same situation and there doesn't appear to be any documentation/blogumentation on this topic. Nevertheless, I figured out a way to use a custom resource provider, with one caveat. The caveat is that I'm in an MVC application so I still have HttpContext.GetLocalResourceObject() available. This is the method that asp.net uses to localize items. The absence of the resource object doesn't stop you from writing our own solution, even if its a direct query of the DB tables. Nevertheless, I thought it was worth pointing out.
While I'm not terribly happy with the following solution, it seems to work. For each validation attribute I want to use I inherit from said attribute and overload the IsValid(). The decoration looks like this:
[RequiredLocalized(ErrorMessageResourceType= typeof(ClassBeginValidated), ErrorMessageResourceName="Errors.GenderRequired")]
public string FirstName { get; set; }
The new attribute looks like this:
public sealed class RequiredLocalized : RequiredAttribute {
public override bool IsValid(object value) {
if ( ! (ErrorMessageResourceType == null || String.IsNullOrWhiteSpace(ErrorMessageResourceName) ) ) {
this.ErrorMessage = MVC_HtmlHelpers.Localize(this.ErrorMessageResourceType, this.ErrorMessageResourceName);
this.ErrorMessageResourceType = null;
this.ErrorMessageResourceName = null;
}
return base.IsValid(value);
}
}
Notes
You need to decorate your code with the derived attribute, not the standard one
I'm using ErrorMessageResourceType to pass the type of the class being validated. By that I mean if I'm in a customer class and validating the FirstName property I would pass typeof(customer). I'm doing this because in my database backend I'm using the full class name (namespace + classname) as a key (the same way a page URL is used in asp.net).
MVC_HtmlHelpers.Localize is just a simple wrapper for my custom resource provider
The (semi-stolen) helper code looks like this ....
public static string Localize (System.Type theType, string resourceKey) {
return Localize (theType, resourceKey, null);
}
public static string Localize (System.Type theType, string resourceKey, params object[] args) {
string resource = (HttpContext.GetLocalResourceObject(theType.FullName, resourceKey) ?? string.Empty).ToString();
return mergeTokens(resource, args);
}
private static string mergeTokens(string resource, object[] args) {
if (resource != null && args != null && args.Length > 0) {
return string.Format(resource, args);
} else {
return resource;
}
}
I have used fluent validation to achieve this. It saves me lots of time. This is what my Globalized validator looks like. It does mean that you don't use data anotations, but sometimes data anotations get a bit big and messy.
Here is an example:
(Errors.Required, Labels.Email and Errors.AlreadyRegistered are in my blobal resources folder.)
public class CreateEmployerValidator : AbstractValidator<CreateEmployerModel> {
public RegisterUserValidator() {
RuleFor(m => m.Email)
.NotEmpty()
.WithMessage(String.Format(Errors.Required, new object[] { Labels.Email }))
.EmailAddress()
.WithMessage(String.Format(Errors.Invalid, new object[] { Labels.Email }))
.Must(this.BeUniqueEmail)
.WithMessage(String.Format(Errors.AlreadyRegistered, new object[] { Labels.Email }));
}
public bool BeUniqueEmail(this IValidator validator, string email ) {
//Database request to check if email already there?
...
}
}
Like I said, it is a move away form data annotations, only because I already have too many annotations on my methods already!
I'll add my findings since I had to fight with this. Maybe it will help someone.
When you derive from RequiredAttribute, it seems to break client side validation. So to fix this I implemented IClientValidatable and implemented the GetClientValidationRules method. Resources.GetResources is static helper method I have that wraps around HttpContext.GetGlobalResourceObject.
The custom required attribute:
public class LocalizedRequiredAttribute : RequiredAttribute, IClientValidatable
{
public LocalizedRequiredAttribute(string resourceName)
{
this.ErrorMessage = Resources.GetResource(resourceName);
}
public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
{
yield return new ModelClientValidationRule
{
ErrorMessage = this.ErrorMessage,
ValidationType= "required"
};
}
}
Usage:
[LocalizedRequired("SomeResourceName")]
public string SomeProperty { get; set; }
And my Resources helper if anyone is interested:
public class Resources
{
public static string GetResource(string resourceName)
{
string text = resourceName;
if (System.Web.HttpContext.Current != null)
{
var context = new HttpContextWrapper(System.Web.HttpContext.Current);
var globalResourceObject = context.GetGlobalResourceObject(null, resourceName);
if (globalResourceObject != null)
text = globalResourceObject.ToString();
}
return text;
}
}