Develop Reference

Form-data is not binding to viewmodel with a generic type

I have an application written using C# on the top of ASP.NET Core 5.0.
I have the following view-model
public class TestVM
{
public Name { get; set; }
public MenuViewModel<string> State { get; set;}
public TestVM()
{
State = MenuViewModel<string>();
}
}
Here is a stripped down version of my MenuViewModel
public class MenuViewModel
{
[BindNever]
public IEnumerable<SelectListItem> Items { get; set; }
}
public class MenuViewModel<T> : MenuViewModel
{
public T Value { get; set; }
}
The problem, is when the post request comes in, the viewModel.State.Value is null. When I evaluate Request.Form I do see the key State.Value with the correct value of CA
Here is a stripped down of my action method in the controller.
[HttpPost, ValidateAntiForgeryToken]
public IActionResult Store(TestVM viewModel)
{
if(ModelState.IsValid)
{
// do some
}
return View(viewModel);
}
How can I bind the form data from the request to State.Value property correctly?
Updated I created an editor-template to allow me to render the MenuVieModel. The ~/Views/Shared/EditorTemplates/MenuViewModel.cshtml contains the following code
#model dynamic
#{
if (!(Model is MenuViewModel m))
{
return;
}
dynamic obj = new System.Dynamic.ExpandoObject();
obj.Class = "form-control";
if (Html.ViewData.ModelMetadata.IsRequired)
{
obj.Required = true;
}
}
#Html.DropDownList("Value", m.Options, Html.ViewData.ModelMetadata.Placeholder, obj)

Firsly,you need know that for each property of the complex type, model binding looks through the sources for the name pattern prefix.property_name. If nothing is found, it looks for just property_name without the prefix.
Here is a working demo you could follow:
Model:
public class TestVM
{
public string Name { get; set; }
public MenuViewModel<string> State { get; set; }
public TestVM()
{
State =new MenuViewModel<string>();
}
}
public class MenuViewModel
{
[BindNever]
public IEnumerable<SelectListItem> Items { get; set; }
}
public class MenuViewModel<T> : MenuViewModel
{
public T Value { get; set; }
}
View:
#model dynamic
#{
if (!(Model is MenuViewModel m))
{
return;
}
dynamic obj = new System.Dynamic.ExpandoObject();
obj.Class = "form-control";
if (Html.ViewData.ModelMetadata.IsRequired)
{
obj.Required = true;
}
}
<form asp-action="Store">
#*change here,And I do not find Options in your MenuViewModel,So I change it to Items*#
#Html.DropDownList("State.Value", m.Items, Html.ViewData.ModelMetadata.Placeholder, obj)
<input type="submit" value="post" />
</form>
Controller:
public IActionResult Index()
{
var model = new MenuViewModel<string>()
{
Items = new List<SelectListItem>() {
new SelectListItem() { Value = "-1", Text = "--- Select ---" },
new SelectListItem() { Value = "org1", Text = "org1" },
new SelectListItem() { Value = "org2", Text = "org2" },
new SelectListItem() { Value = "org3", Text = "org3" }
}
};
return View(model);
}
[HttpPost, ValidateAntiForgeryToken]
public IActionResult Store(TestVM viewModel)
{
if (ModelState.IsValid)
{
// do some
}
return View(viewModel);
}
Result:

construct an object into another object

this should be a stupid problem but i dont know where to start,so i'll ask here.i've got a class named Routing which is binded to a datagrid. Inside this class theres an object from another class:
public class Routing : INotifyPropertyChanged
{
public int Sequenza { get; set; }
private ObservableCollection<Prodotti> availableProducts;
public ObservableCollection<Prodotti> AvailableProducts
{
get { return availableProducts; }
set
{
if (availableProducts != value)
{
availableProducts = value;
OnPropertyChanged("AvailableProducts");
}
}
}
private Prodotti product;
public Prodotti Product
{
get { return product; }
set
{
if (product != value)
{
product = value;
UpdateAvailableCosts();
OnPropertyChanged("Product");
}
}
}
}
and then the Product class:
public class Prodotti
{
public int Product_id { get; set; }
public string Product_description { get; set; }
public int Product_treshold { get; set; }
}
Everything works as intended,and if i just declare the "Sequenza = 1" in the routing the datagrid adds the 1 in the first row/column. But i would like to add more initial values,maybe based on data present in the database. but i cant come up with the constructor for it
Routes.Add(new Routing { Sequenza = 1,Prodotti=... });

Routes.Add(new Routing { Sequenza = 1,Prodotti= new Prodotti{Product_id =1, Product_description = "str", Product_treshold =1} });

EF Adding a new item through interface

Im new to MVC and EF and in a bit of a tangle i have the following Interface:
public interface IReportDataSource
{
IQueryable<PostDetail> PostDetails { get; }
void Save();
}
this database context:
public class ReportDb: DbContext, IReportDataSource
{
public DbSet<PostDetail> PostDetails { get; set; }
public ReportDb()
: base("DefaultConnection")
{
}
void IReportDataSource.Save()
{
SaveChanges();
}
IQueryable<PostDetail> IReportDataSource.PostDetails
{
get { return PostDetails; }
}
}
and this action
[HttpPost]
public ActionResult PostDetails(PostDetailsViewModel viewModel)
{
if (ModelState.IsValid)
{
//save
// var storePost = _db.PostDetails.Single();
var pd = new PostDetail();
pd.Grade = viewModel.Grade;
pd.ContractType = viewModel.SelectedContractType;
pd.Directorate = viewModel.SelectedDirectorate;
pd.Division = viewModel.Division;
pd.HoursPerWeek = viewModel.HoursPerWeek;
pd.Length = viewModel.SelectedContractLength;
pd.LineManager = viewModel.LineManager;
pd.LineManagerContactNumber = viewModel.LineManagerContactNumber;
pd.PositionTitle = viewModel.PositionTitle;
pd.Section = viewModel.Section;
pd.SpecifyDuration = viewModel.SpecifyDuration;
pd.SpecifyEndDate = viewModel.SpecifyEndDate;
_db.Save();
return RedirectToAction("Index", "HomeController");
}
I think I need to be able to call add through my interface to add the new PostDetails object to the datacontext before calling save?

I think _db.PostDetails.Add(pd) before save could help

Is there a name for this creation pattern?

What should I be calling the "BFactory" below. Its not really a Factory since there is no selection of a concrete class happening, and its not necessarily creating an object each time. Its kind of a Pool but the users do not return the Bs they get to the pool after they are done with them. It could be called a Cache but performance is not the primary intention. The intention is that everyone who is using the same BFactory will get the same B when they pass the same A which starts to sound kind of like a singleton-ish.
public class A
{
public int MyProperty { get; set; }
}
public class B
{
public B(A wrapped)
{
Wrapped = wrapped;
}
public A Wrapped { get; set; }
}
public class BFactory
{
private Dictionary<A,B> _created = new Dictionary<A,B>();
public B GetB(A a)
{
if (_created.ContainsKey(a) == false)
{
_created[a] = new B(a);
}
return _created[a];
}
}
here is a slightly more real example:
The value from MyModel is shown in several locations in the app by binding a TextBlock to the ValueString property of MyViewModel. The user can select to present the value as a percent or a decimal and it should be updated in all locations if it is updated in one.
public class MyModel
{
public int Value { get; set; }
}
public class MyViewModel
{
private readonly MyModel _model;
public MyViewModel(MyModel model)
{
_model = model;
}
public string ValueString
{
get { return string.Format(FormatString, _model.Value); }
}
public string FormatString { get; set; }
}
public class MyViewModelFactory
{
private readonly Dictionary<MyModel, MyViewModel> _created = new Dictionary<MyModel, MyViewModel>();
public MyViewModel GetViewModel(MyModel model)
{
if (_created.ContainsKey(model) == false)
{
_created[model] = new MyViewModel(model);
}
return _created[model];
}
}

MVC 3 model binding with underscores

I'm posting json with variables names with underscores (like_this) and attempting to bind to a model that is camelcased (LikeThis), but the values are unable to be bound.
I know I could write a custom model binder, but since the underscored convention is so common I'd expect that a solution already existed.
The action/model I'm trying to post to is:
/* in controller */
[HttpPost]
public ActionResult UpdateArgLevel(UserArgLevelModel model) {
// do something with the data
}
/* model */
public class UserArgLevelModel {
public int Id { get; set; }
public string FirstName { get; set; }
public string Surname { get; set; }
public int ArgLevelId { get; set; }
}
and the json data is like:
{
id: 420007,
first_name: "Marc",
surname: "Priddes",
arg_level_id: 4
}
(Unfortunately I can't change either the naming of either the json or the model)

You can start writing a custom Json.NET ContractResolver:
public class DeliminatorSeparatedPropertyNamesContractResolver :
DefaultContractResolver
{
private readonly string _separator;
protected DeliminatorSeparatedPropertyNamesContractResolver(char separator)
: base(true)
{
_separator = separator.ToString();
}
protected override string ResolvePropertyName(string propertyName)
{
var parts = new List<string>();
var currentWord = new StringBuilder();
foreach (var c in propertyName)
{
if (char.IsUpper(c) && currentWord.Length > 0)
{
parts.Add(currentWord.ToString());
currentWord.Clear();
}
currentWord.Append(char.ToLower(c));
}
if (currentWord.Length > 0)
{
parts.Add(currentWord.ToString());
}
return string.Join(_separator, parts.ToArray());
}
}
This is for your particular case, becase you need a snake case ContractResolver:
public class SnakeCasePropertyNamesContractResolver :
DeliminatorSeparatedPropertyNamesContractResolver
{
public SnakeCasePropertyNamesContractResolver() : base('_') { }
}
Then you can write a custom attribute to decorate your controller actions:
public class JsonFilterAttribute : ActionFilterAttribute
{
public string Parameter { get; set; }
public Type JsonDataType { get; set; }
public JsonSerializerSettings Settings { get; set; }
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
if (filterContext.HttpContext.Request.ContentType.Contains("application/json"))
{
string inputContent;
using (var reader = new StreamReader(filterContext.HttpContext.Request.InputStream))
{
inputContent = reader.ReadToEnd();
}
var result = JsonConvert.DeserializeObject(inputContent, JsonDataType, Settings ?? new JsonSerializerSettings());
filterContext.ActionParameters[Parameter] = result;
}
}
}
And finally:
[JsonFilter(Parameter = "model", JsonDataType = typeof(UserArgLevelModel), Settings = new JsonSerializerSettings { ContractResolver = new SnakeCasePropertyNamesContractResolver() })]
public ActionResult UpdateArgLevel(UserArgLevelModel model) {
{
// model is deserialized correctly!
}