I want to add a [Required] attribute to my DateTime editor template so that I can add the appropriate validation schemes or a DataType.Date attribute so I know when I should only display dates. But I can't figure out how to get the metadata that says which attributes the Editor Template has assigned to it.
The built-in attributes, such as [Required] assign different properties on the metadata (see the blog post I have linked at the end of my answer to learn more). For example:
public class MyViewModel
{
[Required]
public string Foo { get; set; }
}
would assign:
#{
var isRequired = ViewData.ModelMetadata.IsRequired;
}
in the corresponding editor/display template.
And if you had a custom attribute:
public class MyCustomStuffAttribute : Attribute, IMetadataAware
{
public void OnMetadataCreated(ModelMetadata metadata)
{
metadata.AdditionalValues["customStuff"] = "some very custom stuff";
}
}
and a view model decorated with it:
public class MyViewModel
{
[MyCustomStuff]
public string Foo { get; set; }
}
in the corresponding editor/display template you could fetch this:
#{
var myCustomStuff = ViewData.ModelMetadata.AdditionalValues["customStuff"];
}
Also you should absolutely read Brad Wilson's series of blog posts about what ModelMetadata and templates in ASP.NET MVC is and how to use it.
Related
My viewmodel inherits from a class that inherits from an abstract class that has a property with a [Required] attribute, but the rule doesn't appear in the DOM and unobtrusive validation doesn't catch the error.
The display attribute goes through fine, but the validation DOM attributes are not added to the textarea
my view has this:
#model FormPersonView
....
#Html.TextAreaFor(m => m.Description)
#Html.ValidationMessageFor(m => m.Description)
my code has this:
public class FormPersonView : Person
{
//View related stuff
.....
.....
}
public class Person : BasePerson
{
//Person related stuff - validation for these work!
[Required]
public string FirstName { get; set; }
[Required]
public string LastName { get; set; }
}
public abstract class BasePerson
{
//Base person stuff - validation for this doesn't work!
public string Id { get; set; }
[Required]
[Display("Short description of the person")]
public string Description { get; set; }
}
Why does it work with one level of inheritance but not two? It does work on the server side.
Had exactly this problem. While defining the view, the model comes as a type you defined #model FormPersonView. Data annotations will only work on that specific type, even if you have derived properties from children, their data annotations won't be engaged.
The solution that I came up with in my project was to define editor templates for types I needed data annotations to work properly and then calling #EditorFor on those models. Then and only then were data annotations operating as expected.
Hope this help you.
I figured out that property i want to be validated has to have [Required] attribute in C#
(am i right?)
If so -my model is linq generated class - how to add this attribute?
You can do it a couple of ways:
If it's possible, make the field non-nullable in the database. This will make the field required at the data layer.
Create a partial class that adds a property to your model class. Use this property instead of the database-generated property.
For example:
public partial class YourEntity
{
[Required]
public string YourNewProperty
{
get { return this.TheRealProperty; }
set { this.TheRealProperty = value; }
}
}
Hopefully this helps
well, you could always make a new class, as a part of a Data access layer, with the same attributes, just put [required] where you want.
I believe your LINQ classes are partials. With MVC, you can use the "MetatDataTypeAttribute"
Like so
[MetadataType(typeof(UserMetadataSource))]
public partial class User {
}
class UserMetadataSource {
[HiddenInput(DisplayValue = false)]
public int UserId { get; set; }
}
I'm pulling my hair out on this one.
I am trying to implement a multi-step wizard, and i'm using the Html.Serialize html helper in MVC3 Futures. This works well, except one of the properties in my model is a SelectList. I don't want this property serialized (and it blows up when it tries anyways).
I can't use [NonSerialized] because that only works on fields, not properties. I've even tried some of the other normal ways such as [XmlIgnore] (which I didn't think would work anyways).
Can anyone suggest an attribute that will ignore a property in a model when using Html.Serialize?
EDIT:
The error I get when I try to serialize is a InvalidDataContractException. There is this message:
Type 'System.Web.Mvc.SelectList' cannot be serialized. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want serialized with the DataMemberAttribute attribute. If the type is a collection, consider marking it with the CollectionDataContractAttribute. See the Microsoft .NET Framework documentation for other supported types.
However, if I do this then I have to mark all the members with [DataMember] just to exclude 1 property, which seems kind of stupid.
UPDATE:
A quick example of this is this bit of code (make sure to add reference to System.Runtime.Serialization.dll):
Test.cs
[Serializable]
public class Test
{
public int ID { get; set; }
[IgnoreDataMember]
public SelectList TestList { get; set; }
}
HomeController.cs
public ActionResult About()
{
return View(new Test() { ID = 0, TestList = new SelectList(new [] {""})});
}
Home/About.cshtml
#using Microsoft.Web.Mvc
#model MvcApplication3.Models.Test
#Html.Serialize("Test", Model)
This generates the InvalidDataContractException
public class MyViewModel
{
[IgnoreDataMember]
public SelectList Items { get; set; }
...
}
or simply:
public class MyViewModel
{
public IEnumerable<SelectListItem> Items { get; set; }
...
}
I am aware that in a custom display or editor template I can get metadata about the model via ViewData.ModelMetadata, which has properties that indicate whether certain metadata attributes have been defined for the property, such as IsRequired, DisplayName, and so on. But is there anyway I can access custom metadata I've added to the property via custom attributes?
For example, say in my view I have a property like so:
[UIHint("Whizbang")]
[SomeAttribute("foobar")]
public string LeftWhizbang { get; set; }
And I have a custom display template named Whizbang.cshtml with the following content:
#model string
Left Whizbang Value: #Model
What I'd like to do is be able to determine whether the property LeftWhizbang is decorated with the attribute SomeAttribute and, if so, I'd like to access the attribute's Message property (say), namely the value "foobar".
I'd like to be able to do something like this in my template:
#model string
Left Whizbang Value: #Model
#{
SomeAttributeAttribute attr = ViewData.ModelMetadata.GetAttributes(...);
if (attr != null)
{
<text>... and the value is #attr.Message</text>
}
}
Is this at all possible, or am I looking down a dead end?
Sure. First you'll need your attribute which implements IMetadataAware so that DataAnnotationsModelMetadataProvider knows about it
public class TooltipAttribute : Attribute, IMetadataAware {
public TooltipAttribute(string tooltip) {
this.Tooltip = tooltip;
}
public string Tooltip { get; set; }
public void OnMetadataCreated(ModelMetadata metadata) {
metadata.AdditionalValues["Tooltip"] = this.Tooltip;
}
}
You can then access the attribute by creating a helper method:
public static IHtmlString TooltipFor<TModel, TValue>(
this HtmlHelper<TModel> html,
Expression<Func<TModel, TValue>> expression) {
var data = ModelMetadata.FromLambdaExpression<TModel, TValue>(expression, html.ViewData);
if (data.AdditionalValues.ContainsKey("Tooltip"))
return new HtmlString((string)data.AdditionalValues["Tooltip"]);
return new HtmlString("");
}
Since now I've used the excellent FluentValidation
library to validate my model classes. In web applications I use it in conjunction with the jquery.validate plugin to perform client side validation as well.
One drawback is that much of the validation logic is repeated on the client side and is no longer centralized at a single place.
For this reason I'm looking for an alternative. There are many examples out there showing the usage of data annotations to perform model validation. It looks very promising.
One thing I couldn't find out is how to validate a property that depends on another property value.
Let's take for example the following model:
public class Event
{
[Required]
public DateTime? StartDate { get; set; }
[Required]
public DateTime? EndDate { get; set; }
}
I would like to ensure that EndDate is greater than StartDate. I could write a custom
validation attribute extending ValidationAttribute in order to perform custom validation logic. Unfortunately I couldn't find a way to obtain the
model instance:
public class CustomValidationAttribute : ValidationAttribute
{
public override bool IsValid(object value)
{
// value represents the property value on which this attribute is applied
// but how to obtain the object instance to which this property belongs?
return true;
}
}
I found that the CustomValidationAttribute seems to do the job because it has this ValidationContext property that contains the object instance being validated. Unfortunately this attribute has been added only in .NET 4.0. So my question is: can I achieve the same functionality in .NET 3.5 SP1?
UPDATE:
It seems that FluentValidation already supports clientside validation and metadata in ASP.NET MVC 2.
Still it would be good to know though if data annotations could be used to validate dependent properties.
MVC2 comes with a sample "PropertiesMustMatchAttribute" that shows how to get DataAnnotations to work for you and it should work in both .NET 3.5 and .NET 4.0. That sample code looks like this:
[AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = true)]
public sealed class PropertiesMustMatchAttribute : ValidationAttribute
{
private const string _defaultErrorMessage = "'{0}' and '{1}' do not match.";
private readonly object _typeId = new object();
public PropertiesMustMatchAttribute(string originalProperty, string confirmProperty)
: base(_defaultErrorMessage)
{
OriginalProperty = originalProperty;
ConfirmProperty = confirmProperty;
}
public string ConfirmProperty
{
get;
private set;
}
public string OriginalProperty
{
get;
private set;
}
public override object TypeId
{
get
{
return _typeId;
}
}
public override string FormatErrorMessage(string name)
{
return String.Format(CultureInfo.CurrentUICulture, ErrorMessageString,
OriginalProperty, ConfirmProperty);
}
public override bool IsValid(object value)
{
PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(value);
object originalValue = properties.Find(OriginalProperty, true /* ignoreCase */).GetValue(value);
object confirmValue = properties.Find(ConfirmProperty, true /* ignoreCase */).GetValue(value);
return Object.Equals(originalValue, confirmValue);
}
}
When you use that attribute, rather than put it on a property of your model class, you put it on the class itself:
[PropertiesMustMatch("NewPassword", "ConfirmPassword", ErrorMessage = "The new password and confirmation password do not match.")]
public class ChangePasswordModel
{
public string NewPassword { get; set; }
public string ConfirmPassword { get; set; }
}
When "IsValid" gets called on your custom attribute, the whole model instance is passed to it so you can get the dependent property values that way. You could easily follow this pattern to create a date comparison attribute, or even a more general comparison attribute.
Brad Wilson has a good example on his blog showing how to add the client-side portion of the validation as well, though I'm not sure if that example will work in both .NET 3.5 and .NET 4.0.
I had this very problem and recently open sourced my solution:
http://foolproof.codeplex.com/
Foolproof's solution to the example above would be:
public class Event
{
[Required]
public DateTime? StartDate { get; set; }
[Required]
[GreaterThan("StartDate")]
public DateTime? EndDate { get; set; }
}
Instead of the PropertiesMustMatch the CompareAttribute that can be used in MVC3. According to this link http://devtrends.co.uk/blog/the-complete-guide-to-validation-in-asp.net-mvc-3-part-1:
public class RegisterModel
{
// skipped
[Required]
[ValidatePasswordLength]
[DataType(DataType.Password)]
[Display(Name = "Password")]
public string Password { get; set; }
[DataType(DataType.Password)]
[Display(Name = "Confirm password")]
[Compare("Password", ErrorMessage = "The password and confirmation do not match.")]
public string ConfirmPassword { get; set; }
}
CompareAttribute is a new, very useful validator that is not actually
part of
System.ComponentModel.DataAnnotations,
but has been added to the
System.Web.Mvc DLL by the team. Whilst
not particularly well named (the only
comparison it makes is to check for
equality, so perhaps EqualTo would be
more obvious), it is easy to see from
the usage that this validator checks
that the value of one property equals
the value of another property. You can
see from the code, that the attribute
takes in a string property which is
the name of the other property that
you are comparing. The classic usage
of this type of validator is what we
are using it for here: password
confirmation.
It took a little while since your question was asked, but if you still like metadata (at least sometimes), below there is yet another alternative solution, which allows you provide various logical expressions to the attributes:
[Required]
public DateTime? StartDate { get; set; }
[Required]
[AssertThat("StartDate != null && EndDate > StartDate")]
public DateTime? EndDate { get; set; }
It works for server as well as for client side. More details can be found here.
Because the methods of the DataAnnotations of .NET 3.5 don't allow you to supply the actual object validated or a validation context, you will have to do a bit of trickery to accomplish this. I must admit I'm not familiar with ASP.NET MVC, so I can't say how to do this exactly in conjunction with MCV, but you can try using a thread-static value to pass the argument itself. Here is an example with something that might work.
First create some sort of 'object scope' that allows you to pass objects around without having to pass them through the call stack:
public sealed class ContextScope : IDisposable
{
[ThreadStatic]
private static object currentContext;
public ContextScope(object context)
{
currentContext = context;
}
public static object CurrentContext
{
get { return context; }
}
public void Dispose()
{
currentContext = null;
}
}
Next, create your validator to use the ContextScope:
public class CustomValidationAttribute : ValidationAttribute
{
public override bool IsValid(object value)
{
Event e = (Event)ObjectContext.CurrentContext;
// validate event here.
}
}
And last but not least, ensure that the object is past around through the ContextScope:
Event eventToValidate = [....];
using (var scope new ContextScope(eventToValidate))
{
DataAnnotations.Validator.Validate(eventToValidate);
}
Is this useful?