c# - 如何在 asp.net Core Razor Pages 中填充复选框列表？

Question

我正在尝试了解如何在 asp.net Core Razor Pages 中填充复选框列表。考虑以下类:

public class SignupPageModel
{
    public string UserName { get; set; }
    public string Password { get; set; }
    public List<CheckBoxGroup> Hobbies{ get; set; }
}

public class CheckBoxGroup
{
    public int Id { get; set; }
    public string Name { get; set; }
    public bool IsSelected { get; set; }
}

然后从Page我想填充 Hobbies来自数据库的列表(为简单起见编辑了代码片段):

public class SignupModel : PageModel
{
    [BindProperty]
    public SignupPageModel Input { get; set; }

    public void OnGet()
    {
        var model = new SignupPageModel();
        model.Hobbies = _repo.GetHobbiesCheckBoxGroup();
    }
}

并在 View 中显示:

@for (var i = 0; i < Model.Input.Hobbies.Count; i++)
{
    <div class="form-check">
        <input type="checkbox" asp-for="@Model.Input.Hobbies[i].IsSelected"/>
        <label asp-for="@Model.Input.Hobbies[i].IsSelected">@Model.Input.Hobbies[i].Name</label>
        <input type="hidden" asp-for="@Model.Input.Hobbies[i].Id"/>
        <input type="hidden" asp-for="@Model.Input.Hobbies[i].Name"/>
    </div>
 }

但是在渲染 View 时我收到以下错误:

NullReferenceException: Object reference not set to an instance of an object.

在这一行:

@for (var i = 0; i < Model.Input.Hobbies.Count; i++)

我哪里错了？

Answer 1

如果其他人遇到同样的问题，解决方法是更改​​:

public class SignupModel : PageModel
{
    [BindProperty]
    public SignupPageModel Input { get; set; }

    public void OnGet()
    {
        var model = new SignupPageModel();
        model.Hobbies = _repo.GetHobbiesCheckBoxGroup();
    }
}

对此:

public class SignupModel : PageModel
{
    [BindProperty]
    public SignupPageModel Input { get; set; }

    public void OnGet()
    {
        Input = new SignupPageModel();
        Input.Hobbies = _repo.GetHobbiesCheckBoxGroup();
    }
}