I have two models within my model folder called Models, i am trying to pull data from the model to display it in the view, i am aware of only one model statement can be applied to the view. So i have Created a ViewModels which contain the properties that i would like to reference in the view. now when i run the the application im getting a compilation Error which says:
"Compiler Error Message: CS0246: The type or namespace name 'Models' could not be found (are you missing a using directive or an assembly reference?)"
View Models Code
public class MainModelscs <T> where T :class
{
public StoreAudit StoreAudit { get; set; }
public StoreQuestions StoreQuestions { get; set; }
public IPagedList<T> IndexList { get; set; }
}
model properties in view
#model PopMarketing.ViewModel.MainModelscs<Models>
You need to specify the full namespace of the Models type which you are using. Something like this:
#model PopMarketing.ViewModel.MainModelscs<PopMarketing.Models.ListItemType>
Related
Let's say I have the following input tag which utilizes the built-in tag helper:
#model ProductViewModel
<label asp-for="Product.Id"></label>
In my case, this expands into the following:
<label for="Product_Id">Id</label>
I see that asp-for is expecting a ModelExpression:
In tag helper implementations, I often see a property like the following:
public ModelExpression For { get; set; }
It appears that this is automatically populated when the tag helper is used.
Is there a way to instantiate a ModelExpression directly in C#?
I.e. something like this:
var exp = new ModelExpression("Product.Id",...)
I'd like to be able to generate "Product_Id" and "Id" from Product.Id as the input tag helper did.
As far as I know, you can specify that your property is to be set to the name of some property on the View's Model object by declaring your property with the ModelExpression type. This will enable any developer using your property to get IntelliSense support for entering a property name from the Model object. More importantly, your code will be passed the value of that property through the ModelExpression's Model property.
Sample code as below:
[HtmlTargetElement("employee-details")]
public class EmployeeDetailTagHelper : TagHelper
{
[HtmlAttributeName("for-name")]
public ModelExpression EmployeeName { get; set; }
[HtmlAttributeName("for-designation")]
public ModelExpression Designation { get; set; }
public override void Process(TagHelperContext context, TagHelperOutput output)
{
output.TagName = "EmployeeDetails";
output.TagMode = TagMode.StartTagAndEndTag;
var sb = new StringBuilder();
sb.AppendFormat("<span>Name: {0}</span> <br/>", this.EmployeeName.Model);
sb.AppendFormat("<span>Designation: {0}</span>", this.Designation.Model);
output.PreContent.SetHtmlContent(sb.ToString());
}
}
Code in the View page:
#model WebApplication7.Models.EmployeeViewModel
<div class="row">
<employee-details for-name="Name" for-designation="Designation"></employee-details>
</div>
Code in the Model
public class EmployeeViewModel
{
public string Name { get; set; }
public string Designation { get; set; }
}
From above code, you can see that we could custom the attribute name. More detail information about using the ModelExpression, check the following links:
Creating Custom Tag Helpers With ASP.NET Core MVC
Expression names
I'd like to be able to generate "Product_Id" and "Id" from Product.Id
as the input tag helper did.
Besides, do you mean you want to change the Product. Id to Product_Id, in my opinion, I'm not suggesting you change it, because generally we can use "_" as a separator in the property name. So, if we are using Product.Id, it means the Product's Id property, and the Product_Id means there have a Product_Id property.
To answer the question:
Is there a way to instantiate a ModelExpression directly in C#"
Yes you can, through IModelExpressionProvider and its CreateModelExpression method. You can get an instance of this interface through DI.
Now, if you're already in your view and working with tag helpers, Zhi Lv's answer is all you need, as the functionality is built-in and much easier to use. You only need IModelExpressionProvider for when you're in your Razor Page, Controller, or perhaps some custom middleware. Personally, I find this functionality useful for my Ajax handlers that need to return one of my ViewComponents that has a ModelExpression argument (so that I can easily call it from my Pages/Views too.)
To call CreateModelExpression, you'll need a strongly-typed instance of ViewData. In Razor Pages, this is as easy as casting the ViewData property to the strongly-typed instance of your PageModel's type (presuming you don't have a page model hierarchy):
var viewData = (ViewDataDictionary<IndexModel>)ViewData;
If you're using MVC and you're in the controller, that won't exist yet. Best you can do is make your own instance.
var viewData = new ViewDataDictionary<ErrorViewModel>(new EmptyModelMetadataProvider(),
new ModelStateDictionary());
Once you get your strongly-typed ViewData instance, you can obtain your desired ModelExpression like this, just like using a lambda expression in your views:
var myPropertyEx = _modelExpressionProvider.CreateModelExpression(viewData,
m => m.MyProperty);
I am trying to come up with the best pattern for passing data to my _layout.cshtml page.
I am toying with creating a common base class from which all view specific models derive. This base class would be recognized by my _layout.cshtml and used to fill in details about the user and load proper images in the header, etc. For example, here is a snippet of it.
public abstract class ViewModelBase
{
public string Username { get; set; }
public string Version { get; set; }
}
At the top of my _layout.cshtml I have...
#model MyProject.Web.Controllers.ViewModelBase
I need a common area to hydrate the information required by the model, and am planning to use the following pattern...
Each action method creates and hydrates a model derived from
ViewModelBase.
The action completes.
I create a ActionFilterAttribute and override OnActionExecuted to cast the
current Result to ViewModelBase.
If the conversion is successful, then I populate the ViewModelBase details with the relevant data.
Here are my questions...
Is the use of a ActionFilterAttribute (OnActionExecuted) a good pattern for what I am trying to do?
I am not able to see how to get the Result created in the action from the HttpActionExecutedContext. How is this done?
I follow the same approach and use a base ViewModel class which all my other viewModels inherit from.
Then, I have a base controller that all controller inherit from. In there, I have one method that takes care of initializing the view model:
protected T CreateViewModel<T>() where T : ViewModel.BaseViewModel, new()
{
var viewModelT = new T {
HeaderTitle = "Welcome to my domain",
VisitorUsername = this.VisitorUsername,
IsCurrentVisitorAuthenticated = this.IsCurrentVisitorAuthenticated,
//...
};
return viewModelT;
}
Then on each controller, when I want to create the view model, I simply call the base controller's method:
var vm = base.CreateViewModel<MyPageCustomViewModel>();
I have a form displaying fields from 2 tables in database.
I want to validate this form using Data Annotation model validation technique in MVC4.
I am confused whether Data Annotation validation attributes should be applied to individual models(tables) or should I create separate model consisting of fields from both tables.
You should create a new model containing the information you want to display on your view. This specific model has a name: it's called view model. You should always pass view models to your views from the controller actions and your controller actions should always take view models as parameters. Then you could decorate the properties on this view model with validation attributes.
You can do both things. You can decorate your domain model classes and view models. Both things are correct. The thing is that for your view, it's better to use a view model instead of model classes. No need to expose the whole domain model in you view
Just add using System.ComponentModel.DataAnnotations;namespace and add the attributes you need on each property.
For example:
public class BankAccount
{
[Required]
public Person Person { get; set; }
[Required]
public AccountType AccountType { get; set; }
[Required, StringLength(256)]
public string BankName { get; set; }
}
So i have a situation where i have common base type but i need to map to a different view based on the child type.
It looks like i can use a generic mapping class to handle the inheritance
http://geekswithblogs.net/nharrison/archive/2010/07/09/inheriting-a-class-map-in-fluent-nhibernate.aspx
But how can i conditionally map to a different view based on the child type? I see an EntityType property but it says its obsolete and will be made private in the next version.
As an example i have a base class of ContactInfo is standard between contact types but the values come from different places depending on the contact type, this I'll handle through the sql view.
using any mapping the referenced entity comes from a different table
class ContactInfo
{
public virtual long Id { get; set; }
public virtual ContactDetails Details { get; set; }
}
public ContactInfoMap
{
...
ReferencesAny(x => x.Details)
.EntityIdentifierColumn("details_id")
.EntityTypeColumn("contactType")
.IdentityType<long>()
.AddMetaValue<FooContactDetails>("1")
.AddMetaValue<BarContactDetails>("4");
}
I am trying to set up EF to work on WCF and keeping the domain class models EF Agnostic.
The code is organized into 3 projects. (I am taking a stab a DDD - I am very new to it but am looking forward t learning more)
Project: QA - Domain Layer. Contains the DataContract models/entities.
References
QA.Data
Project: QA.Data - Data Layer. Contains the context and EDMX (code generation stragtegy = "none")
References
Entity Framework/System.Data.Entity
Project: QA.Repository - Data Access/Repository. Contains the repository classes
References
QA [Domain Layer]
QA.Data [Data Layer]
Entity Frame/System.DataEntity
My understanding is that the domain layer can reference the data layer but the data layer should never reference the domain. The problem that this presents is that my Domain Models/Classes are defined in the Domain layer but the Context which creates and returns them is in the Data layer. In order for my context to know to return a "Widget" object it would need a reference to the Domain layer which defined the "Widget"
My (failed) solution : My solution was to create interfaces for each Domain Model and place them in the data layer. The context would return ... IdbSet ... These interfaces would, in turn, be implemented by the Domain Models, therefore keeping my data layer from directly needing to reference my domain (which causes illegal circular references anyway). The domain models were originally contructed using "ADO.NET DbContext Generator w/WCF Support" T4 templates. This process resulted in the inclusion of the [KnownType(typeof(IWidgetPiece))] at the beginning of of the widget class defin ition. (A Widget has a navigation property ... ICollection ...)
The problem appears when I attempt to access the service, I get the following error
'QA.Data.IWidgetPiece' cannot be added to list of known types since
another type 'System.Object' with the same data contract name
'http://www.w3.org/2001/XMLSchema:anyType' is already present. If
there are different collections of a particular type - for example,
List and Test[], they cannot both be added as known types.
Consider specifying only one of these types for addition to the known
types list.
I can change these to the concrete implementations ... [KnownType(typeof(WidgetPiece))] ... but I continue to get this error because the navigation property they are referring to is still returning an IWidgetPiece interface type which it MUST do in order to satify the interface implementation.
I am trying to figure out how to keep things appropriately divided and still have the context returning what it should. the context returning Interfaces still doesn't "sit" right with me for this and other reasons but I cannot think of another way to do this, and even this is presenting the aforementioned issue. HELP!
Some code to hopefully clarify my previous ramblings ...
namespace QA.Data
{
public interface IWidgetPiece
{
String ID { get; set; }
}
public interface IWidget
{
String ID { get; set; }
ICollection<IWidgetPiece> Pieces;
}
public partial class WidgetEntities : DbContext
{
IDbSet<IWidget> Widgets { get; set; }
IDbSet<IWidgetPiece> WidgetPieces { get; set; }
}
}
namespace QA
{
[KnownType(typeof(IWidgetPiece))]
// [KnownType(typeof(WidgetPiece))]
[DataContract(IsReference = true)]
public partial class Widget : QA.Data.IWidget
{
[DataMember]
public String ID { get; set; }
[DataMember]
public virtual ICollection<IWidgetPiece> Pieces { get; set; }
}
[DataContract(IsReference = true)]
public partial class WidgetPiece : QA.Data.IWidgetPiece
{
[DataMember]
public string ID { get; set; }
}
}
namespace QA.Repository
{
public class WidgetRepository
{
public List<Widget> GetWidgetbyID(String sId)
{
WidgetEntities context = new WidgetEntities();
List<IWidget> objs = context.Widgets.Where(b => b.ID == "78").ToList();
List<Widget> widgetList = new List<Widget>();
foreach (var iwidget in widgetList)
widgetList((Widget)iwidget);
return widgetList;
}
}
}
Do you really want / need two separate models i.e. your data access layer model (edmx) and your "real" domain model? The whole point of an ORM framework like EF is so you can map your domain model to your database tables, using mappings between the physical (database) conceptual model.
Since EF4.1, you can construct your domain model and then in your data access layer map that to your database directly using a fluent API. You can also elect to reverse-engineer your POCO domain model from a database if you want to quickly get up an running.
It just seems a bit of unnecessary complexity to create an entire EF class model, only to then have to map it again into another class model (which will most likely be fairly close to the EF-generated one).