I am creating a record in a table that has foriegn key in it. The foriegn key is getting passed in the query string and I have set the value in the ViewBag. I have added this to the form but it will not work.
Here is the code from the controller:
public ActionResult Create(int propertyId)
{
ViewBag.storagePropertyId = propertyId;
return View();
}
Here is the code from the view.
#Html.HiddenFor(model => model.propertyId, new { value =ViewBag.propertyId })
Is this how I should be doing this? If so, is there a problem with that form
Why not just set the value of the Model.PropertyID in the controller, or better yet in a viewmodel.
ViewModel
public class MyViewModel()
{
public int PropertyID { get; set; }
public MyViewModel() { }
public MyViewModel(int propertyID)
{
this.PropertyID = propertyID;
}
}
Action Result
public ActionResult Create(int propertyId)
{
return View(new MyViewModel(propertyId));
}
View
#model MyViewModel
#Html.HiddenFor(m => m.PropertyID)
Then the value of the Hidden field will contain the value of the property ID.
Related
I have a PUT Rest API that I want to do binding from both body and route parameters.
Code
[HttpPut("{Id}/someStuffApi")]
public ActionResult UpdateStatus([FromBody] StatusRequest StatusRequest)
{
// code ...
}
And the model class is
public class StatusRequest
{
[FromRoute(Name = "Id")]
[Required(ErrorMessage = "'Id' attribute is required.")]
public string Id { get; set; }
[FromBody]
[Required(ErrorMessage = "'Status' attribute is required.")]
public string Status { get; set; }
}
When I made a request to this API, the Id is not mapped to the model even though I added the FromRoute attribute explicitly. Any suggestions?
The [FromBody] model binding will effectively override the [FromRoute] option in your model class. This is by design (why, I'm not sure, but an MS decision). See the "[FromBody] attribute" section of this doc: https://learn.microsoft.com/en-us/aspnet/core/mvc/models/model-binding. As pointed out there: "When [FromBody] is applied to a complex type parameter, any binding source attributes applied to its properties are ignored." So adding the "[FromRoute]" attribute inside your model does nothing...it's ignored. You can remove both of those attributes from your model.
So the way around this is to put the route binding in the Put action as a method parameter and then manually add it to your model in the controller before using the model.
[HttpPut("{Id}/someStuffApi")]
public ActionResult UpdateStatus(int Id, [FromBody] StatusRequest StatusRequest)
{
StatusRequest.Id = Id;
// remaining code...
}
The downside to this method is that the Required attribute cannot remain on the Id parameter. It will be null at the time of model binding and if you have .Net Core 3.1 automatic model validation active, then that will always return a 422. So if you would have to manually check that yourself before adding it to the model.
If you want even more flexibility, you can look at something like the HybridModelBinding NuGet package that allows various combinations of model binding using attributes. But this is a 3rd party dependency that you may not want. (https://github.com/billbogaiv/hybrid-model-binding/)
You can use custom model binding,here is a demo:
TestModelBinderProvider:
public class TestModelBinderProvider : IModelBinderProvider
{
private readonly IList<IInputFormatter> formatters;
private readonly IHttpRequestStreamReaderFactory readerFactory;
public TestModelBinderProvider(IList<IInputFormatter> formatters, IHttpRequestStreamReaderFactory readerFactory)
{
this.formatters = formatters;
this.readerFactory = readerFactory;
}
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context.Metadata.ModelType == typeof(StatusRequest))
return new StatusBinder(formatters, readerFactory);
return null;
}
}
Startup.cs:
services.AddMvc()
.AddMvcOptions(options =>
{
IHttpRequestStreamReaderFactory readerFactory = services.BuildServiceProvider().GetRequiredService<IHttpRequestStreamReaderFactory>();
options.ModelBinderProviders.Insert(0, new TestModelBinderProvider(options.InputFormatters, readerFactory));
});
StatusBinder:
public class StatusBinder: IModelBinder
{
private BodyModelBinder defaultBinder;
public StatusBinder(IList<IInputFormatter> formatters, IHttpRequestStreamReaderFactory readerFactory)
{
defaultBinder = new BodyModelBinder(formatters, readerFactory);
}
public async Task BindModelAsync(ModelBindingContext bindingContext)
{
// callinng the default body binder
await defaultBinder.BindModelAsync(bindingContext);
if (bindingContext.Result.IsModelSet)
{
var data = bindingContext.Result.Model as StatusRequest;
if (data != null)
{
var value = bindingContext.ValueProvider.GetValue("Id").FirstValue;
data.Id = value.ToString();
bindingContext.Result = ModelBindingResult.Success(data);
}
}
}
}
StatusRequest:
public class StatusRequest
{
[Required(ErrorMessage = "'Id' attribute is required.")]
public string Id { get; set; }
[Required(ErrorMessage = "'Status' attribute is required.")]
public string Status { get; set; }
}
Action:
[HttpPut("{Id}/someStuffApi")]
public ActionResult UpdateStatus(StatusRequest StatusRequest)
{
return Ok();
}
result:
I am using entity frame work in my mvc core application. I am also using dependency injection technique. Now i want to get the value of new record identity column. I am using the code as..
public interface IGenericRepositoryStudent<T> where T : class
{
void Add(T item);
}
public class GenericRepositoryStudent<T> : IGenericRepositoryStudent<T> where T : class
{
private eerp_studentContext _context;
private DbSet<T> _dbSet;
public GenericRepositoryStudent(eerp_studentContext context)
{
_context = context;
_dbSet = _context.Set<T>();
}
public void Add(T item)
{
_dbSet.Add(item);
_context.SaveChanges();
}
}
Controller:
public class StudentController : Controller
{
private IStudentRepository _dbSet;
public StudentController(IStudentRepository dbSet)
{
_dbSet = dbSet;
}
public long Add([FromBody]Student _student)
{
if (ModelState.IsValid)
{
_dbSet.Add(acJournal);
long _id = _student.id; // value of _id is always 0.
return _id;
}
}
}
Apparently every T that you want to Add has a Primary Key. You want the value of this primary Key after the T has been added and changes are saved.
This means, that you can't add objects of every class, you can only add classes that have a Primary Key.
The easiest, and a very type safe way (checked by compiler) is to allow only adding of object that have a primary key.
// interface of objects that have Id (primary key)
public interface IID
{
public long Id {get; set;}
}
If your database uses another type for primary keys like int, or GUID, use this other type as return type
public interface IGenericRepositoryStudent<T> where T : IID
{
T Add(T item);
}
public class GenericRepositoryStudent<T> : IGenericRepositoryStudent<T> where T : IID
{
...
public T Add(T itemToAdd)
{
T addedItem = _dbSet.Add(item);
_context.SaveChanges();
return addedItem
}
}
Usage:
class Student : IID
{
public long Id {get; set;} // primary key
...
}
public class StudentController : Controller
{
...
public T Add([FromBody]Student _student)
{
if (ModelState.IsValid)
{
return _dbSet.Add(_student);
}
}
}
I chose to return the complete T instead of only the Id, because if you need some of the properties of the added item, you don't need to fetch the item you just added. Besides this is just the return value of DbSet.Add(T)
If you really want, just return the Student's Id.
Im new to MVC2/3 so keep that in mind. Also, using Ajax or jQuery is NOT an option.
I have a web page where the user must choose an item out of a dropdown list and then hit a "Filter" button. (Clicking this button will simply trigger the default POST action in my controller and return a filtered list of results.
I have everything working except I am running into one issue. When the Filter action is complete and returns control back to my view, the dropdown list contents are lost (ie, null). The results are returned no problem, it's just that my dropdown list is blank - thus preventing user from selecting another item out of the list.
Am I supposed to re-fill the dropdown list on the Filter action or is there a cleaner way to do this?
Here is a snapshot of my code:
My ViewModel
public class MyViewModel {
[DisplayName("Store")]
public IEnumerable<Store> StoreList { get; set; }
public string SelectedStore { get; set; }
}
My View (Index.cshtml)
#using (Html.BeginForm()) {
<h2>Search</h2>
#Html.LabelFor(m => m.StoreList)
#Html.DropDownListFor(m => m.SelectedStore, new SelectList(Model.StoreList, "StoreCode", "StoreCode"), "Select Store")
<input type="submit" value="Filter" />
}
My Controller:
public class MyController : Controller
{
public ActionResult Index() {
MyViewModel vm = new MyViewModel();
var storelist = new List<Store>();
storelist.Add(new Store { StoreCode = "XX" });
storelist.Add(new Store { StoreCode = "YY" });
storelist.Add(new Store { StoreCode = "ZZ" });
vm.StoreList = storelist;
return View(vm);
}
[HttpPost]
public ActionResult Index(MyViewModel model, string SelectedStore, FormCollection collection) {
if (ModelState.IsValid) {
/* this works, model state is valid */
/* BUT, the contents of model.StoreList is null */
}
return View( model);
}
}
Yes, you have to repopulate any models (including ViewData) that are passed to the view. Remember, it's a stateless system, your controller is re-instantiated with every call and starts effectively from scratch.
I would do it thus:
public class MyController : Controller
{
private List<Store> GetStoreList()
{
List<Store> StoreList = new List<Store>();
// ... Do work to populate store list
return StoreList;
}
public ActionResult Index() {
MyViewModel vm = new MyViewModel();
vm.StoreList = GetStoreList();
return View(vm);
}
[HttpPost]
public ActionResult Index(MyViewModel model, string SelectedStore, FormCollection collection) {
if (ModelState.IsValid) {
/* this works, model state is valid */
/* BUT, the contents of model.StoreList is null */
}
model.StoreList = GetStoreList();
return View( model);
}
}
Short answer is yes, you need to refill the drop-down list in the Filter action. ASP.NET MVC isn't WebForms - there is no ViewState to preserve the contents of your list.
Again fill the dropdown as mvc don't have View state
[HttpPost]
public ActionResult Index(MyViewModel model, string SelectedStore, FormCollection collection) {
if (ModelState.IsValid) {
/* this works, model state is valid */
/* BUT, the contents of model.StoreList is null */
}
model.StoreList = GetStoreList();
return View( model);
}
I am having a problem with a selectlistitem, the values of which are being retrieved from a database.
It is displaying the list of items in the view, but it is not passing through (POSTing) the selected value into the model.
So when the user submits, or the page reloads due to validation, the select value (PositionApplied) is empty.
Can anyone give me some pointers as to where I am going wrong?
In my controller:
[HttpGet]
public ActionResult Index()
{
PopulateJobsDropdown();
return View();
}
private void PopulateJobsDropdown()
{
IEnumerable<SelectListItem> items = _service.GetJobs()
.Select(c => new SelectListItem
{
Value = c.JobID.ToString(),
Text = c.JobTitle
});
ViewData["PositionApplied"] = items;
}
In my ViewModel
public IEnumerable<SelectListItem> PositionApplied { get; set; }
In my View
<%=Html.DropDownList("PositionApplied")%>
Thanks in advance for any pointers!
So, where is the code line that get's the
ViewData["PositionApplied"] = items;
into
public IEnumerable<SelectListItem> PositionApplied { get; set; }
something like:
this.PositionApplied = ViewData["PositionApplied"] as IEnumerable<SelectListItem>;
and you can simple use in your View:
<%
IEnumerable<SelectListItem> PositionApplied =
ViewData["PositionApplied"] as IEnumerable<SelectListItem>;
%>
...
<%= Html.DropDownList("myDropDOwnId", PositionApplied) %>
or is there some of automagical happening under MVC2 that I'm not aware about? As I use the example I give you, all the time.
Added
in order to avoid Linq to Entities error (if you are using it) change your method to
private void PopulateJobsDropdown()
{
IQueryble<Your_Table> jobs = _service.GetJobs();
List<SelectListItem> items = new List<SelectListItem>();
foreach(var job in jobs)
items.add(new SelectListItem
{
Value = c.JobID.ToString(),
Text = c.JobTitle
});
ViewData["PositionApplied"] = items;
}
and all will work fine.
An example, if I have a class named Order with a field referencing a Customer, and then an Order form with an drop down list (<%= Html.DropDownListFor(e => e.Customer.ID, new SelectList(...)) %>) for setting the Customer the model binder will create an empty Customer with only the ID set. This works fine with NHibernate but when validation is added to some of the fields of the Customer class, the model binder will say these fields are required. How could I prevent the model binder from validating these references?
Thanks!
Ages old question, but I figured I'd answer anyways for posterity. You need a custom model binder in this situation to intercept that property before it attempts to bind it. The default model binder will recursively attempt to bind properties using their custom binder, or the default one if not set.
The override you're looking for in DefaultModelBinder is GetPropertyValue. This is called over all properties in the model, and by default it calls back to DefaultModelBinder.BindModel - the entry point to the whole process.
Simplified model:
public class Organization
{
public int Id { get; set; }
[Required]
public OrganizationType Type { get; set; }
}
public class OrganizationType
{
public int Id { get; set; }
[Required, MaxLength(30)]
public string Name { get; set; }
}
View:
<div class="editor-label">
#Html.ErrorLabelFor(m => m.Organization.Type)
</div>
<div class="editor-field">
#Html.DropDownListFor(m => m.Organization.Type.Id, Model.OrganizationTypes, "-- Type")
</div>
Model Binder:
public class OrganizationModelBinder : DefaultModelBinder
{
protected override object GetPropertyValue(
ControllerContext controllerContext,
ModelBindingContext bindingContext,
System.ComponentModel.PropertyDescriptor propertyDescriptor,
IModelBinder propertyBinder)
{
if (propertyDescriptor.PropertyType == typeof(OrganizationType))
{
var idResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName + ".Id");
if (idResult == null || string.IsNullOrEmpty(idResult.AttemptedValue))
{
return null;
}
var id = (int)idResult.ConvertTo(typeof(int));
// Can validate the id against your database at this point if needed...
// Here we just create a stub object, skipping the model binding and
// validation on OrganizationType
return new OrganizationType { Id = id };
}
return base.GetPropertyValue(controllerContext, bindingContext, propertyDescriptor, propertyBinder);
}
}
Note that in the View we create the DropDownListFor the model.foo.bar.Id. In the model binder, ensure that this is added to the model name as well. You can leave it off of both, but then DropDownListFor has a few issues finding the selected value without pre-selecting it in the SelectList you send it.
Finally, back in the controller, be sure to attach this property in your database context (if you're using Entity Framework, others might handle differently). Otherwise, it isn't tracked and the context will attempt to add it on save.
Controller:
public ActionResult Create(Organization organization)
{
if (ModelState.IsValid)
{
_context.OrganizationTypes.Attach(organization.Type);
_context.Organizations.Add(organization);
_context.SaveChanges();
return RedirectToAction("Index");
}
// Build up view model...
return View(viewModel);
}