ASP.NET mvc 3 model binding with list of strings - asp.net-mvc

I am currently using model binding and ASP.NET MVC 3 and .NET 4.0.
View Model Class:
public class BasicViewModel
{
[Display(Name = #"Names")]
[Required(ErrorMessage = #"Names is required")]
[DisplayFormat(ConvertEmptyStringToNull = true)]
List<string> Names { get; set; }
[Display(Name = #"Email")]
[Required(ErrorMessage = #"Email is required")]
string Email { get; set; }
}
Controller
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult NameEmail( BasicViewModel basicModel)
{
// some manipulation of data
}
View in cshtml file (razor view engine)
// model declared here using #model BasivViewModel
// only required part shown labels part of code removed
#Html.TextBoxFor(model => model.Names)
...
#Html.TextBoxFor(model => model.Email)
...
The model binding provided by ASP.NET MVC binds the string Email to null if it is empty but binds the List Names to empty string (""). I want it to be null. I made the binding work using JavaScript by parsing the values of form fields on click of submit button. But i want the asp.net model binding to do this. Furthermore, it would be great if there is some field in Data Annotations class like Required for this functionality. I tried this Null Display Text Property and refer to the remarks section. Is there a solution or is this how it is implemented?. I am not sure whether i have understood this part of model binding correctly.

By default, if the field, representing an array, is in the html, the controller will receive an array of length 0. However, to make the array null, you can define a custom ModelBinder.
public class MyModelBinder : DefaultModelBinder
{
public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
if (bindingContext.ModelType == typeof(List<string>))
{
HttpRequestBase request = controllerContext.HttpContext.Request;
// Check to see if any of the elements the array is not empty and
// returns null if they all are.
return request.Form.GetValues("Names").Any(x => !string.IsNullOrWhiteSpace(x)) ?
base.BindModel(controllerContext, bindingContext) :
null;
//You can also remove empty element from the array as well, by using
// a where clause
}
return base.BindModel(controllerContext, bindingContext);
}
}
Alternatively, you can also implement IModelBinder instead of DefaultModelBinder.
The next step is to register the custom binder in your Application_Start function in the Global.asax.cs file.
ModelBinders.Binders.Add(typeof(List<string>), new MyModelBinder());
This basically tells the mvc engine to use the MyModelBinder whenever the field is List<string>
To know more about modelbinder, goolge "MVC custom model binding". Let me know you go :)

Related

Uppercase attribute that converts the input to uppercase

I am working in MVC4 and want to define a model using an Uppercase attribute. The idea would be that the presence of the Uppercase attribute would cause the model value to be converted to uppercase when it arrived at the server.
At the moment I have the following code within the model:
[Required]
[Display(Name="Account Code")]
[StringValidation(RegExValidation.AccountCode, Uppercase=true)]
public string Account
{
get { return _account; }
set
{
if (value != null)
_account = value.ToUpper();
}
}
But what I would really like is this:
[Required]
[Display(Name="Account Code")]
[StringValidation(RegExValidation.AccountCode)]
[Uppercase]
public string Account { get; set; }
I think that I may need to create the Uppercase attribute as a ValidationAttribute to ensure it gets fired when the model hits the server. But that seems a bit wrong, as I'm not really validating the data. Is there a better way?
Also, is there any way to ensure the invocation order on the attributes? I really want to convert the data to uppercase before the custom StringValidation attribute fires, as this checks the case of the text in the regex pattern.
To add a bit of background to this, I want to reduce the need to add code to uppercase the data. The nirvana would be a single attribute, which updates the data on the way into the server, either in the model binding or validation stage. This attribute can then be referenced in the StringValidation attribute to amend the RegEx value used in its checks. I can also then lookup this attribute in a custom TextBoxFor helper method, such that I can add text-transform: uppercase so it looks correct on the client side.
Does anyone have any ideas out there?
I have managed to get this working, to a point, so here's my solution for others to appraise.
Once point to note was that the full solution couldn't be achieved because I couldn't get the Modelmetadata inside the StringValidation.IsValid() attribute. The particular issue I had here was that I could get the Metadata, however I could not get the PropertyName from it, only the DisplayName. There were multiple options out there, but the fact that some of my properties have the same DisplayName means that I couldn't be sure that the ProprtyName was the one I was actually validating.
Here's the code for the ValidationAttribute:
public class StringValidationAttribute : ValidationAttribute, IClientValidatable, IMetadataAware {
private bool _uppercase;
public StringValidationAttribute(bool uppercase = false) {
_uppercase = uppercase;
}
...
public void OnMetadataCreated(ModelMetadata metadata)
{
metadata.AdditionalValues["Uppercase"] = _uppercase;
}
}
I then created a new IModelBinder implementation:
public class StringBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
ValueProviderResult result = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
if (result == null)
return null;
if (bindingContext.ModelMetadata.AdditionalValues.ContainsKey("Uppercase")) {
if ((bool)bindingContext.ModelMetadata.AdditionalValues["Uppercase"]])
return result.AttemptedValue.ToUpper();
}
return result.AttemptedValue;
}
}
And registered that in myGlobal.asax file:
ModelBinders.Binders.Add(typeof(string), new StringBinder());
The code so far will cause any string input coming into MVC to be converted to Uppercase if it has StringValidationAttribute attached to it on the model, and where the uppercase indicator has been set.
Next, to achieve my desire of making the html forms be uppercase too, I implemented a new EditorTemplate named string.cshtml. In this view I added:
RouteValueDictionary htmlAttributes = new RouteValueDictionary();
if ((bool)ViewData.ModelMetadata.AdditionalValues["Uppercase"]) {
htmlAttributes.Add("class", "Uppercase");
}
#Html.TextBox("", Model, htmlAttributes)
With the CSS as;
.Uppercase {
text-transform: uppercase;
}
Hope this post helps some others out there.
For Web API purpose it is better to convert the incoming json to uppercase or lowercase.
public class ToUpperCase : JsonConverter
{
public override bool CanConvert(Type objectType)
{
return objectType == typeof(string);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
return reader.Value.ToString().ToUpper();
}
}
[Display(Name = "PNR NAME")]
[JsonConverter(typeof(Annotations.ToUpperCase))]
public string PNR { get; set; }
OR Globally;
protected void Application_Start()
{
AreaRegistration.RegisterAllAreas();
//.......... others
JsonMediaTypeFormatter jsonFormatter = GlobalConfiguration.Configuration.Formatters.JsonFormatter;
JsonSerializerSettings jSettings = new Newtonsoft.Json.JsonSerializerSettings();
jSettings.Converters.Add(new UpperCaseStringConverter());
jsonFormatter.SerializerSettings = jSettings;
}
You're right, ValidationAttribute is not the right fit. It seems like doing this at the Model Binding stage would be a better idea. See this article for a detailed explanation of how to customize this behavior.
Based on the information provided there, I believe you should be able to create an attribute based on CustomModelBinderAttribute like this:
[AttributeUsage(AttributeTargets.Property)]
public class UppercaseAttribute : CustomModelBinderAttribute
{
public override IModelBinder GetBinder()
{
return new UppercaseModelBinder();
}
private class UppercaseModelBinder : DefaultModelBinder
{
public override object BindModel(
ControllerContext controllerContext,
ModelBindingContext bindingContext)
{
var value = base.BindModel(controllerContext, bindingContext);
var strValue = value as string;
if (strValue == null)
return value;
return strValue.ToUpperInvariant();
}
}
}
I have not tested this. Let me know if it works or not.
NOTE:
I'm adding on to this post because until I discovered the approach I now use, I read this and tried all above unsuccessfully.
I generally use a two part process when dealing with forcing text data to be formatted as uppercase. 1. at the view and 2. at the controller
At the view layer so that the user knows data is going to be used in the uppercase form. This can be down through htmlAttributes used in the EditorFor HTML helper.
#HTML.EditorFor(model => model.Access_Code, new { htmlAttributes = new Style= "text-transform:uppercase"}})
Now this only forces the data seen and entered by the user to uppercase and not the data sent to the server. To do that requires some code in the associated method in the controller.
I add the ToUpper() method to the target attribute of the object being passed back to the contoller. Here is hypothetical example showing this.
public ActionResult verify(int? id)
{
var userData = db.user.Where (i=> i.userID == id).Single();
userData.Access_Code = userData.Access_Code.ToUpper();
...
}

ASP.NET Web API Model Binding

I'm using Web API within ASP .NET MVC 4 RC, and I have a method that takes a complex object with nullable DateTime properties. I want the values of the input to be read from the query string, so I have something like this:
public class MyCriteria
{
public int? ID { get; set; }
public DateTime? Date { get; set; }
}
[HttpGet]
public IEnumerable<MyResult> Search([FromUri]MyCriteria criteria)
{
// Do stuff here.
}
This works well if I pass a standard date format in the query string such as 01/15/2012:
http://mysite/Search?ID=1&Date=01/15/2012
However, I want to specify a custom format for the DateTime (maybe MMddyyyy)... for example:
http://mysite/Search?ID=1&Date=01152012
Edit:
I've tried to apply a custom model binder, but I haven't had any luck applying it to only DateTime objects. The ModelBinderProvider I've tried looks something like this:
public class DateTimeModelBinderProvider : ModelBinderProvider
{
public override IModelBinder GetBinder(HttpActionContext actionContext, ModelBindingContext bindingContext)
{
if (bindingContext.ModelType == typeof(DateTime) || bindingContext.ModelType == typeof(DateTime?))
{
return new DateTimeModelBinder();
}
return null;
}
}
// In the Global.asax
GlobalConfiguration.Configuration.Services.Add(typeof(ModelBinderProvider), new DateTimeModelBinderProvider());
The new model binder provider is created, but GetBinder is only called once (for the complex model parameter, but not for each property within the model). This makes sense, but I would like to find a way to make it to use my DateTimeModelBinder for DateTime properties, while using the default binding for non-DateTime properties. Is there a way to override the default ModelBinder and specify how each property is bound?
Thanks!!!
Consider setting your view-model's Date property to type string
Then either write a utility function to handle the mapping between the viewmodel type and the domain-model type:
public static MyCriteria MapMyCriteriaViewModelToDomain(MyCriteriaViewModel model){
var date = Convert.ToDateTime(model.Date.Substring(0,2) + "/" model.Date.Substring(2,2) + "/" model.Date.Substring(4,2));
return new MyCriteria
{
ID = model.ID,
Date = date
};
}
or use a tool like AutoMapper, like this:
in Global.asax
//if passed as MMDDYYYY:
Mapper.CreateMap<MyCriteriaViewModel, MyCriteria>().
.ForMember(
dest => dest.Date,
opt => opt.MapFrom(src => Convert.ToDateTime(src.Date.Substring(0,2) + "/" src.Date.Substring(2,2) + "/" src.Date.Substring(4,2)))
);
and in the controller:
public ActionResult MyAction(MyCriteriaViewModel model)
{
var myCriteria = Mapper.Map<MyCriteriaViewModel, MyCriteria>(model);
// etc.
}
From this example it might not seem that AutoMapper is providing any added value. It's value comes when you are configuring several or many mappings with objects that generally have more properties than this example. CreateMap will automatically map properties with the same name and type, so it saves lots of typing and it's much DRYer.

ASP.NET MVC3 Custom Model Binder Issues

I have an applicant model that contains a list of tags:
public class Applicant
{
public virtual IList<Tag> Tags { get; protected set; }
}
When the form is submitted, there is an input field that contains a comma-delimited list of tags the user has input. I have a custom model binder to convert this list to a collection:
public class TagListModelBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var incomingData = bindingContext.ValueProvider.GetValue("tags").AttemptedValue;
IList<Tag> tags = incomingData.Split(',').Select(data => new Tag { TagName = data.Trim() }).ToList();
return tags;
}
}
However, when my model is populated and passed into the controller action on POST, the Tags property is still an empty list. Any idea why it isn't populating the list correctly?
The problem is you have the protected set accessor in Tags property. If you change that into public as below things will work fine.
public class Applicant
{
public virtual IList<Tag> Tags { get; set; }
}
A model binder only binds submitted values. It does not bind values rendered in the view.
You need to create a custom EditorTemplate to render the tags as you need them.
MVC can already bind to a List, I would recommend using the built in technology that already does what you need.
I didn't notice any code about adding the binder, did you add your ModelBinder to the Binders?
protected void Application_Start()
{
ModelBinders.Binders.Add(typeof(IList<Tag>), new TagListModelBinder());
}

ASP.NET MVC (4) - Bind properties in a certain order

Is there a way to force binding of properties A and B before C?
There's Order property in the System.ComponentModel.DataAnnotations.DisplayAttribute class, but does it affect binding order?
What i'm trying to achieve is
page.Path = page.Parent.Path + "/" + page.Slug
in a custom ModelBinder
Why not implement the Page property as:
public string Path{
get { return string.Format("{0}/{1}", Parent.Path, Slug); }
}
?
I would have initially recommended Sams answer as it would have not involved any binding of the Path property at all. You mentioned that you could concatenate the values using a Path property as this would cause lazy loading to occur. I imagine therefore you are using your domain models to display information to the view. I would therefore recommend using view models to display only the information required in the view (then use Sams answer to retrieve the path) and then map the view model to the domain model using a tool (i.e. AutoMapper).
However, if you continue to use your existing model in the view and you cannot use the other values in the model, you can set the path property to the values provided by the form value provider in a custom model binder after the other binding has occurred (assuming no validation is to be performed on the path property).
So lets assume you have the following view:
#using (Html.BeginForm())
{
<p>Parent Path: #Html.EditorFor(m => m.ParentPath)</p>
<p>Slug: #Html.EditorFor(m => m.Slug)</p>
<input type="submit" value="submit" />
}
And the following view model (or domain model as the case may be):
public class IndexViewModel
{
public string ParentPath { get; set; }
public string Slug { get; set; }
public string Path { get; set; }
}
You can then specify the following model binder:
public class IndexViewModelBinder : DefaultModelBinder
{
protected override void OnModelUpdated(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
//Note: Model binding of the other values will have already occurred when this method is called.
string parentPath = bindingContext.ValueProvider.GetValue("ParentPath").AttemptedValue;
string slug = bindingContext.ValueProvider.GetValue("Slug").AttemptedValue;
if (!string.IsNullOrEmpty(parentPath) && !string.IsNullOrEmpty(slug))
{
IndexViewModel model = (IndexViewModel)bindingContext.Model;
model.Path = bindingContext.ValueProvider.GetValue("ParentPath").AttemptedValue + "/" + bindingContext.ValueProvider.GetValue("Slug").AttemptedValue;
}
}
}
And finally specify that this model binder is to be used by using the following attribute on the view model:
[ModelBinder(typeof(IndexViewModelBinder))]

DefaultModelBinder Problem with nested levels + other binders

I have what I would think is a somewhat normal situation where I need to bind form posts to an "order" model. This model has a few levels of information to it:
Order.Billing.FirstName
Order.Billing.Address.City
Order.Billing.Address.Country
Using the DefaultModelBinder, if I POST a form to an action that takes this Order model as the param, the following fields JustWork(TM):
<%=Html.TextBox("Billing.FirstName")%>
<%=Html.TextBox("Billing.Address.City")%>
This field does not:
<%=Html.TextBox("Billing.Address.Country")%>
The wrinkle I have is with the country property. In our case, Address.Country returns a Country class instance (ISO2/3/Name/Code logic). It is not a string. Not surprise that it doesn't work by default.
My first thought was to create a CountryModelBinder (inherit DefaultModelBinder) and ModelBinders.Binders.Add it to the type of Country. When I do that, CountryModelBinder never gets called in the scenerio above.
My second thought was to create an AddressModelBinder (inherit DefaultModelBinder) and bind it to our Address type. While that does get called, the SetProperty call for "Country" has an empty value, even though the form has posted a field called "Billing.Address.Country".
After some tinkering, it appears that the model binding behavior only calls CreateModel when the model is the top level class the action wants, and all other binders have their BindPropery/SetProperty called for child properties.
In other words, if I create model binders for Order, OrderAddress(Billing), Address, and Country. For the action that takes an order, only OrderModelBinder.CreateModel is called. ORderAddress and Address.BindProperty/SetProperty are called for some things, and sometimes SetProperty value argument is empty when it was clearly posted in a name that matches the other field property mappings.
It's easy enough to just add code to OrderModelBinder to pull Billing.Address.Country out of Request.Form. But I have multiple models that use Address and having all of them do that seems broken.
What am I missing here? Is there a way to have the CountryModelBinder actually get called in this case? I would think that the CountryModelBinder should get called when Billing.Address.Country is mapped to the Country property of the Address binder.
I've tried doing what you've done here, appearntly on MVC3 it does indeed work if I provide a model binder for that type.
This is just a proof of concept to show that it DOES WORK, and shouldn't be seen as even close to production level code:
Models:
public class SimpleModel
{
public string Value { get; set; }
public int Other { get; set; }
}
public class ComplexModel
{
public SimpleModel Complexity {get;set;}
public string StrVal { get; set; }
}
some binder:
public class MBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
if ( bindingContext.ModelType == typeof(SimpleModel))
{
var simpleModel= new SimpleModel();
simpleModel.Other = 1;
simpleModel.Value = controllerContext.HttpContext.Request.Form["Complexity"];
return cm;
}
return null;
}
}
in global asax:
ModelBinders.Binders.Add(typeof (SimpleModel), new MBinder());
code in View:
#model ComplexModel
#using ( Html.BeginForm() )
{
<fieldset>
#Html.LabelFor(x => x.Complexity)
#Html.TextBoxFor(x => x.Complexity)
</fieldset>
<fieldset>
#Html.LabelFor(x => x.StrVal)
<br />
#Html.EditorFor(x => x.StrVal)
</fieldset>
<input type="submit" />
}
Controller:
public ActionResult Index()
{
return View();
}
[HttpPost]
public ActionResult Index(ComplexModel model)
{
return RedirectToAction("Index");
}
BTW in MVC 3 a better option would be to use the IModelBinderProvider interface, but I just wanted to show something that would work.

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