Cast an object in the page view (template) inside asp-for="object"-CodePudding

How to cast an object inside the quotes("") (asp-for="object") in the page view?

I have a parent class Person and two child classes Student and Teacher.

variable:
Person person;

I want to cast it to behave as the child class.. something like:

asp-for="(Person)person.grade"

asp-for="((Person)person).grade"

But neither code works. How can I cast an object inside of asp-for quotes ("")?

CodePudding user response：

<input asp-for="...."/>

The input tag helper binds a ModelExpression property to the attribute. ModelExpressions are a bit weird. Essentially, the razor compiler translates your code into something equivalent to;

 = ModelExpressionProvider.CreateModelExpression<TModel>(m => m.[your attribute text], ...);

However, if your attribute starts with a @, that leading m. is not inserted. In other words, you should be able to do the following;

<input asp-for="@(Person)Model.person.grade" />

At least that should compile. Whether that solves your actual problem is another matter.

CodePudding user response：

This is the whole code structure:

//parent class

public abstract class Person
{
    //code
}

//child class

public class Teacher : Person
{
    //code
    public double Salary { get; set; }
}

//2nd child class

public class Student : Person
{
    //code
    public double Grade { get; set; }
}

//in WinForms I could access child classes components by down casting

public partial class FormSchool : Form
{
    //code
    Person Person;
    double grade = ((Student)Person).Grade;
    //code
}

//in razor pages as well in .cs files

public class IndexModel : PageModel
{
    //code
    [BindProperty]
    public Person Person { get; set; }
    //code
}

//but when it came to the page templates I got stuck how to do it inside of the asp-for=".." quotes

// the following code doesn't work
<select asp-for="((Student)Person).Grade" asp items="Html.GetEnumSelectList<Grades>()"></select>
neither this:
<input asp-for="@(Person)Model.person.grade"/>

For now I am just using child class to create objects and modelBinding them to the view, but I would like to just have one object and cast it regarding some specific child class uses... in the templates.