I am using ASP.NET MVC2 and Entity Framework. I am going to simplify the situation a little; hopefully it will make it clearer, not more confusing!
I have a controller action to create address, and the country is a lookup table (in other words, there is a one-to-many relationship between Country and Address classes). Let's say for clarity that the field in the Address class is called Address.Land. And, for the purposes of the dropdown list, I am getting Country.CountryID and Country.Name.
I am aware of Model vs. Input validation. So, if I call the dropdown field formLand - I can make it work. But if I call the field Land (that is, matching the variable in Address class) - I am getting the following error:
"The parameter conversion from type
'System.String' to type 'App.Country'
failed because no type converter can
convert between these types."
OK, this makes sense. A string (CountryID) comes from the form and the binder doesn't know how to convert it to Country type. So, I wrote the converter:
namespace App {
public partial class Country {
public static explicit operator Country(string countryID) {
AppEntities context = new AppEntities();
Country country = (Country) context.GetObjectByKey(
new EntityKey("AppEntities.Countries", "CountryID", countryID));
return country;
}
}
}
FWIW, I tried both explicit and implicit. I tested it from the controller - Country c = (Country)"fr" - and it works fine. However, it never got invoked when the View is posted. I am getting the same "no type converter" error in the model.
Any ideas how to hint to the model binder that there is a type converter?
Thanks
A type converter is not the same as an explicit or implicit conversion, it's an object that converts values between various types.
I think you need to create a class inherited from TypeConverter that converts between Country and other types, and apply the TypeConverterAttribute to your class to specify the converter to use :
using System.ComponentModel;
public class CountryConverter : TypeConverter
{
// override CanConvertTo, CanConvertFrom, ConvertTo and ConvertFrom
// (not sure about other methods...)
}
[TypeConverter(typeof(CountryConverter))]
public partial class Country
{
...
}
Related
I am attempting to create Web API controller in F# which returns objects from Entity Framework. SharpObject and SharpContext are my object and DbContext respectively defined in a c# project.
/// Retrieves values.
[<RoutePrefix("api2/values")>]
type ValuesController() =
inherit ApiController()
let values = [| "value1"; "value2" |]
/// Gets all values.
[<Route("")>]
member x.Get() : IEnumerable<SharpObject> =
use context = new SharpContext()
context.SharpObjects.ToList() :> IEnumerable<SharpObject>
Here is SharpObject with the SerializableAttribute.
[Serializable]
public class SharpObject
{
[Key]
public virtual int Id { get; set; }
public virtual string Description { get; set; }
}
The error that I am getting is this:
The type System.Data.Entity.DynamicProxies.SharpObject_3A697B5C46C0BF76858FEAFC93BFED36DD8D4CA2CEACBB178D2D3C38BB2D2052 was not expected. Use the XmlInclude or SoapInclude attribute to specify types that are not known statically.
When I de-compile this using ILSpy, it looks like this:
[Route("")]
public IEnumerable<SharpObject> Get()
{
SharpContext context = new SharpContext();
IEnumerable<SharpObject> result;
try
{
result = (IEnumerable<SharpObject>)context.SharpObjects.ToList<SharpObject>();
}
finally
{
IDisposable disposable = context as IDisposable;
if (disposable != null)
{
disposable.Dispose();
}
}
return result;
}
What is the best way to get my list to show through in f#?
This happens because the object that you get from EF is not, in fact, of type SharpObject, but rather of that scarily named type, which inherits from SharpObject. This type is called "proxy" and is dynamically generated by EF in order to provide certain services (such as lazy loading, see below).
Because your action is declared as returning IEnumerable<SharpObject>, the default WebAPI's XML serializer expects to find object of that type, and so rightly complains upon finding an object of different type.
One temporary, bandaid-style fix that you can try is to remove the virtual keywords from your entity (why do you have them there, anyway?). It is the presence of the virtual keywords that causes EF to generate the proxy type. Absent virtual, no proxy will be generated, thus making the XML serializer happy.
This, however, will not work once you extend your model to include navigation properties with lazy loading. Those properties, you must make virtual, otherwise lazy loading won't work.
So the correct fix is not to use the same type for both DB-facing DTO and client-facing DTO. Use different types.
Using the same type for these two purposes may seem "convenient" at first, but this road quickly leads to numerous problems. One of small technical problems you have already discovered. But even absent those, conceptually, you almost never, ever want to just serve up your DB records directly to the untrusted user. Some of possible consequences include security holes, badly factored UI code, badly factored database structure, performance problems, and so on.
Bad idea. Don't do it.
P.S. This doesn't actually have anything to do with F#.
I am new in mvc so forgive me if the question is stupid but I want to do the best I can. So, my situation is that:
I have created a model and decorated like
Partial Public Class App_Modules
<Required>
<Remote("CheckForDuplicate", "Validation")>
<Display(Name:="Code")>
Public Property code As String
<Required>
<Display(Name:="Description")>
Public Property name As String
End Class
As you can see, the code column must be remote validated.
In my ValidationController I have the code
Public Function CheckForDuplicate(code As String) As JsonResult
Dim data = db.App_Modules.Where(Function(p) p.code.Equals(code, StringComparison.CurrentCultureIgnoreCase)).FirstOrDefault()
If data IsNot Nothing Then
Return Json("This code already exists",JsonRequestBehavior.AllowGet)
Else
Return Json(True, JsonRequestBehavior.AllowGet)
End If
End Function
End Class
Everything works fine! Now I want to do the same for another model with the same field "code". Is there any way to pass the model name to the function so instead of the line
Dim data = db.**App_Modules**.Where(Function(p) p.code.Equals(code, StringComparison.CurrentCultureIgnoreCase)).FirstOrDefault()
I could have something like
Dim data = db.**TABLENAME**.Where(Function(p) p.code.Equals(code, StringComparison.CurrentCultureIgnoreCase)).FirstOrDefault()
So the function would be generic and can be called from other models too?
I am not sure of the syntax in VB but you could modify your CheckForDuplicate function to accept a generic parameter that represents your Model class and pass that to the Set function of your DBContext. you will also need to define an interface for your Model that contains the Code property. Sample code in c# is as follows.
public JsonResult CheckForDuplicate<T>(string code) where T : IModelWithCode
{
var data = db.Set<T>().Where(t => t.Code.Equals(code));
....
}
public interface IModelWithCode
{
string Code { get; set; }
}
Hopefully that will get you started in the right direction.
I don't think this can be done or at least easily.
I would stick with the simple here: create a Select Case and check in the tables depending on the parameter passed (model name).
Dim exist = false;
Select Case myModel
Case "Model1"
exist = db.Model1Table.Where(Function(p) p.code.Equals(code, StringComparison.CurrentCultureIgnoreCase)).Any()
Case "Model2"
exist = db.Model2Table.Where(Function(p) p.code.Equals(code, StringComparison.CurrentCultureIgnoreCase)).Any()
End Select
If each table has different layout or you have to do some other checks... you are free to do the special thing in each case.
UPDATE:
Here you can see an article showing how to pass other fields to the validator action.
You should create a Hidden Field to hold the Model name.
http://www.codeproject.com/Articles/674288/Remote-Validation-in-MVC-Simple-Way-to-Pass-the-F
Other resource: MVC Remote Attribute Additional Fields
I am trying to realize valition on data type. I have used DataAnnotations, but for data type it's not showing customized message
for example when I' am trying enter string data into int typed field. How I can customize messages in this case?
If I had to guess, you sound like you want a custom message to display when validating one or more fields in your model. You can subclass the DataAnnotations.ValidationAttribute class and override the IsValid(object) method and finally setting a custom ErrorMessage value (where ErrorMessage already belongs to the ValidationAttribute class)
public class SuperDuperValidator : ValidationAttribute
{
public override bool IsValid(object value)
{
bool valid = false;
// do your validation logic here
return valid;
}
}
Finally, decorate your model property with the attribute
public class MyClass
{
[SuperDuperValidator(ErrorMessage="Something is wrong with MyInt")]
public int MyInt { get; set; }
}
If you're using out-of-the-box MVC3, this should be all you need to propertly validate a model (though your model will probably differ/have more properties, etc) So, in your [HttpPost] controller action, MVC will automagically bind MyClass and you will be able to use ModelState.IsValid to determine whether or not the posted data is, in fact, valid.
Pavel,
The DataAnnotations DataType attribute does not affect validation. It's used to decide how your input is rendered. In such a case, David's solution above works.
However, if you want to use only the built-in validation attributes, you probably need to use the Range attribute like this:
[Range(0, 10, ErrorMessage="Please enter a number between 0 and 10")]
public int MyInt { get ; set ;}
(Of course, you should really be using the ErrorMessageResourceName/Type parameters and extract out hard-coded error message strings into resx files.)
Make sure to let MVC know where to render your error message:
<%= Html.ValidationMessageFor(m => m.MyInt) %>
Or you can just use EditorForModel and it will set it up correctly.
I don't think this has been answered because I have the same issue.
If you have a Model with a property of type int and the user types in a string of "asd" then the MVC3 framework binding/validation steps in and results in your view displaying "The value 'asd' is not valid for <model property name or DisplayName here>".
To me the poster is asking can this message that the MVC3 framework is outputting be customized?
I'd like to know too. Whilst the message is not too bad if you label your field something that easily indicates an number is expected you might still want to include additional reasons so it says something like:
"The value 'asd' is not valid for <fieldname>; must be a positive whole number."
So that the user is not entering value after value and getting different error messages each time.
I am having a weird issue in ASP.NET MVC with objects not being updated with UpdateModel when passed a formCollection. UpdateModel does not appear to be working properly when the object being updated is created through reflection.
Scenario: I have an application which has approximately 50 lookup tables--each of which includes exactly the same schema including typical fields like id, title, description, isactive, and createdon. Rather than build 50 views, I wanted to have a single view which could display the data from all of the lookup tables. I created an Interface called IReferenceEntity and implemented it in each of the POCOs representing my lookup tables.
Using this interface, I am able to easily populate a view with a record from the lookup table. (I pass the items to the view via the following.)
System.Web.Mvc.ViewPage<MyNamespece.IReferenceEntity>
From the database to the view, every thing works perfectly.
However, when I attempt to update the model on post, I am running into some problems.
If I explicitly declare an object reference like the following, every thing works perfectly and the values of my object are updated with the values from my form. Hence, I can then update the database.
AccountStatus a = new AccountStatus();
UpdateModel(a, formCollection.ToValueProvider());
Unfortunately, hard coding the object type would completely defeat the reason for using an interface.
(A primary objective of the application is to be able to dynamically add new tables such as lookup tables without having to do anything "special". This is accomplished by reflecting on the loaded assemblies and locating any classes which implement a specific interface or base class)
My strategy is to determine the concrete type of the object at postback and then create an instance of the type through reflection. (The mechanism I use to determine type is somewhat primitive. I include it as a hidden field within the form. Better ideas are welcome.)
When I create an instance of the object using reflection through any of the following methods, none of the objects are being updated by UpdateModel.
Type t = {Magically Determined Type}
object b = Activator.CreatorInstance(t);
UpdateModel(b, formCollection.ToValueProvider());
Type t = {Magically Determined Type}
var c = Activator.CreatorInstance(t);
UpdateModel(c, formCollection.ToValueProvider());
Type t = {Magically Determined Type}
IReferenceEntity d = Activator.CreatorInstance(t);
UpdateModel(d, formCollection.ToValueProvider());
Note: I have verified that the objects which are being created through relection are all of the proper type.
Does anyone have any idea why this might be happening? I am somewhat stumped.
If I was really "hard up", I could create factory object which would many instantiate any one of these reference entity/lookup objects. However, this would break the application's ability to allow for new lookup tables to be added and discovered transparently and is just not quite as clean.
Also, I could try deriving from an actual ReferenceEntity base class as opposed to an interface, but I am doubtful whether this would make any difference. The issue appears to be with using reflection created objects in the modelbinder.
Any help is appreciated.
Anthony
Augi answered this on ASP.NET forums. It worked with only a couple of minor modifications. Thank you Augi.
The problem is that [Try]UpdateModel methods allow to specify model type using generic parameter only so they don't allow dynamic model type specification. I have created issue ticket for this.
You can see TryModelUpdate method implementation here. So it's not difficult to write own overload:
public virtual bool TryUpdateModelDynamic<TModel>(TModel model, string prefix, string[] includeProperties, string[] excludeProperties, IDictionary<string, ValueProviderResult> valueProvider) where TModel : class
{
if (model == null)
{
throw new ArgumentNullException("model");
}
if (valueProvider == null)
{
throw new ArgumentNullException("valueProvider");
}
//Predicate<string> propertyFilter = propertyName => BindAttribute.IsPropertyAllowed(propertyName, includeProperties, excludeProperties);
IModelBinder binder = Binders.GetBinder( /*typeof(TModel)*/model.GetType());
ModelBindingContext bindingContext = new ModelBindingContext()
{
Model = model,
ModelName = prefix,
ModelState = ModelState,
//ModelType = typeof(TModel), // old
ModelType = model.GetType(),
// new
//PropertyFilter = propertyFilter,
ValueProvider = valueProvider
};
binder.BindModel(ControllerContext, bindingContext);
return ModelState.IsValid;
}
Does your IReferenceEntity contain setters on the properties as well as getters? I would think that the last sample would work if the interface had property setters, though you'd have to cast it to get it to compile.
Type t = {Magically Determined Type}
IReferenceEntity d = Activator.CreatorInstance(t) as IReferenceEntity;
UpdateModel(d, formCollection.ToValueProvider());
Normally the reason that it won't set a property on a class is because it can't find a public setter method available to use via reflection.
Just a quick "another thing to try":
UpdateModel(d as IReferenceEntity, formCollection.ToValueProvider());
Not sure if that will work, and I haven't tried it myself, but it's the first thing that came to mind.
If I get a chance later I'll peek at the Default Model Binder code and see if there's anything in there that is obvious...
I have a custom viewmodel which serialized using a JsonResult. The ViewModel has some properties which have to be public, but at the same time these properties should not be visible in the resulting Json output.
I've already tried using the [NonSerialized] attribute, but that did not seem to have any effect.
Is there any simple way to do this? Or would I have to code my own result type (in which case I probably won't bother)?
You can put a [ScriptIgnore] attribute on the members that shouldn't be serialized. See ScriptIgnoreAttribute Class in MSDN for an example.
Just create an interface to return instead of a class.
public interface IMyViewModel {
string MyPublicProperty { get; set; }
}
Then create a class that inherits the interface
public class MyViewModel : IMyViewModel {
public string MyPublicProperty { get; set; }
public string MyNotSoPublicProperty { get; set; }
}
And return the interface, not the class, in the Controller Action
public JsonResult MyJson(){
IMyViewModel model = new MyViewModel();
return Json(model);
}
And the resulting JSON will be
{
'MyPublicProperty': ''
}
One of the challenges in client-side scripting is, that if you're changing your classes, you have no idea whether you're destroying the client-side implementation or not. If you use interface types in your JSON, you understand that if you change the interface, you're doing something that potentially may be killing the client side implementation. And it also saves you from double-checking the client side in vain if you're changing something that is NOT in the inteface (thus not being serialized).
Also, many times, your ViewModels might have large collections or complex types in them that you don't necessarily want to output to the client. These might take a long time to serialize or expose information that simply does not belong into the client code. Using interfaces will make it more transparent to know what is being in the output.
Also, using attributes such as [ScriptIgnore] on a property only applies to a specific scenario (JavaScript Serialization) forcing you to face the exact same problem if you're later serializing to XML for example. This would unnecessarily litter your viewmodels with tons of attributes. How many of them you really want in there? Using intefaces applies anywhere and no viewmodel needs to be littered with extra attributes.
Have a look at JSON.NET from James Newton-King. It'll do what you're looking for.
Extend the JavaScriptConverter class to not include properties with the NonSerializedAttribute. Then you can create a custom ActionResult that uses your JavaScriptConverter to serialize the object.
This creates a solid and testable class without having to (re)generate wrapper classes or using anonymous objects.
You can create a wrapper class that exposes only those properties that you want in the JsonResult. In the example below, Cow has 2 properties - "Leg" and "Moo". Suppose you want to only expose "Leg" as a property. Then
Dim cw as CowWrapper = New CowWrapper(c)
will return a wrapper class that only exposes "Leg". This is also useful for things like DataGridView if you only want to display some subset of the properties.
Public Class Cow
Public ReadOnly Property Leg() as String
get
return "leg"
end get
end Property
Public ReadOnly Property Moo() as String
get
return "moo"
end get
end Property
end class
Public Class CowWrapper
Private m_cow as Cow = Nothing
Public Sub New(ByVal cow as Cow)
m_cow = cow
end Sub
m_cow = cow
Public ReadOnly Property Leg() as String
get
return m_cow.Leg()
end get
end Property
end Class
Not exactly the answer you're looking for, but you can cheat Json() using the following code and anonymous classes:
MyModel model = ...;
return Json(new MyModel {model.Prop1, model.Prop2});
I needed the answer to this for ASP.NET Core 6.x and couldn't find it.
I finally found the answer and it is :
[System.Text.Json.Serialization.JsonIgnore]
Here's an example in a class
class Sample{
// Item will not be serialized
[System.Text.Json.Serialization.JsonIgnore]
String Item{get;set;}
// Count will be serialized
int Count{get;set;}
}