Razor 页面 PageModel 正在返回 Null 属性

Question

Why is this razor page returning a null property for Model.People?

People.cshtml.cs

public class PeopleModel : PageModel
{
    [BindProperty]
    public List<PeopleObj> People { get; set; }

    public void OnGet()
    {
        List<PeopleObj> People = GetPeople().ToList();//returns 4 people
    }
}

People.cshtml

@page
@model MyProject.Pages.PeopleModel

@foreach (var item in Model.People){
//Model.People is null 
}

What happens is the OnGet gets called and the People list populated, but then when the view is hit, the view throws System.NullReferenceException: 'Object reference not set to an instance of an object.' on the Model.People. People is null for the view. I don't understand why it is getting overwritten with a null value after being set in the OnGet.

EDIT Seems like the problem is declaring the type. I would still like to know why this breaks the model.

List<PeopleObj> People =

Answer 1

Because you use List<PeopleObj> People = GetPeople().ToList();//returns 4 people ,you just create a new list,you didn't initialize [BindProperty]public List<PeopleObj> People { get; set; } [BindProperty]public List<PeopleObj> People { get; set; } [BindProperty]public List<PeopleObj> People { get; set; } . So when you use foreach,the list(Model.People) is null.null cannot be foreach.

People:

Solution:

If you want to set the property of PeopleModel.You can change

List<PeopleObj> People = GetPeople().ToList();

to

People = GetPeople().ToList();

And then you can still get the edited data from People in OnPost handler.

Here is a demo:

Model:

public class PeopleObj 
        {
            public int Id { get; set; }
            public string Name { get; set; }
    
        }

People.cshtml:

<form method="post">
    @{var count = 0;}
    @foreach (var item in Model.People)
    {
        <div class="form-group">
            <label class="control-label">Id</label>
            <input class="form-control" value="@item.Id" name="People[@count].Id"/>
        </div>
        <div class="form-group">
            <label class="control-label">Name</label>
            <input class="form-control" value="@item.Name" name="People[@count].Name" />

        </div>
        count++;
    }
    <input type="submit" value="submit" />
</form>

People.cshtml.cs:

public class PeopleModel : PageModel
    {
        [BindProperty]
        public List<PeopleObj> People { get; set; }

        public void OnGet()
        {
            People = new List<PeopleObj> { 
                new PeopleObj{  Id=1, Name="person1"},
                new PeopleObj{  Id=2, Name="person2"},
                new PeopleObj{  Id=3, Name="person3"},
                new PeopleObj{  Id=4, Name="person4"}
            };
        }
        public void OnPost()
        {
            //get edited data from People
            List<PeopleObj> EditedPeople = People;
        }
    }

result: