Question

我试图弄清楚如何在asp.net Core Razor Pages中填充一个复选框列表。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中，我想从数据库中填充Hobbies列表（为简化起见，对代码段进行了编辑）：

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

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

并在视图中显示：

@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>
 }

但是渲染View时出现以下错误：

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++)

我要去哪里错了？

Answer 1

万一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();
    }
}

如何在asp.net Core Razor Pages中填充复选框列表？

1 个答案: