Razor Pages PageModel 正在返回 Null 属性

Question

为什么此 razor 页面为 Model.People 返回空值属性？

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 
}

调用 OnGet 并填充人员列表会发生什么，但是当点击视图时，视图会在 Model.People 上抛出 System.NullReferenceException：'Object reference not set to an instance of an object.'。 People 对于视图为 null。我不明白为什么它在 OnGet 中设置后会被空值覆盖。

编辑似乎问题在于声明类型。我仍然想知道为什么这会破坏模型。

List<PeopleObj> People =

Answer 1

因为你使用List<PeopleObj> People = GetPeople().ToList();//returns 4 people，你只是创建了一个新列表，你没有初始化[BindProperty]public List<PeopleObj> People { get; set; }。所以当你使用 foreach 时，list(Model.People) 是 null.null cannot be foreach.

人：

解决方案：

如果要设置PeopleModel.You的属性可以改

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

到

People = GetPeople().ToList();

然后您仍然可以在 OnPost 处理程序中从 People 获取编辑后的数据。

这是一个演示：

型号：

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;
        }
    }

结果：

Razor Pages PageModel 正在返回 Null 属性

Razor Pages PageModel is Returning Null Property

c#

razor

asp.net-core

razor-pages

.net-5