c# - checked 属性为 false 时，单选按钮默认被选中？

Question

我正在尝试生成单选按钮，有条件地检查选中的属性，如果该值存在于数据库中，则应该选择它，否则选中的属性为 false。所以最初数据库中没有行，所有单选按钮的 checked 属性也是 false，但它仍然在 UI 上被选中，见下图

所以不知道这是默认行为还是遗留的任何错误，下面是我的代码

View 模型

public class CompanionProductVersion1ViewModel
{
    [Required(ErrorMessage = "Please select companion release - 1")]
    public string CompanionReleaseRadio1 { get; set; }
    public List<CompanionReleaseRadio1> CompanionReleaseRadios1 { get; set; }
}

public class CompanionReleaseRadio1
{
    public string RadioID { get; set; }
    public string RadioText { get; set; }
    public bool Checked { get; set; }
}

查看

@model PlatformLifecyclePortal.Web.ViewModel.CompanionProductVersion1ViewModel

<div class="mt-5">
    <div class="d-flex pb-3">
        <h2>Companion Release - 1</h2>
    </div>

    <div class="border border-dark p-5">
        <div class="row"><h6><b>@Session["Release"]</b></h6></div>
        <div class="row"><p><b>@Session["Feature"]</b></p></div>
        <div class="row">@Html.ValidationMessageFor(m => m.CompanionReleaseRadio1, "", new { @class = "help-block text-danger", @style = "color:red;" })</div>
        <div class="row"><div class="col-sm-9">&nbsp;</div></div>

        <div class="row">

            @using (Html.BeginForm())
            {
                <div class="form-group row">
                    @foreach (var companionReleases1 in Model.CompanionReleaseRadios1)
                    {
                        <div class="col-sm-4">
                            @Html.RadioButtonFor(model => Model.CompanionReleaseRadio1, companionReleases1.RadioID, new { id = "CompanionReleaseRadio2" + companionReleases1.RadioID, @checked = companionReleases1.Checked }) <span class="checkbox-label">@companionReleases1.RadioText</span>
                        </div>
                    }
                </div>

                <div class="row">
                    <div class="col-sm-9">
                        <button type="submit" class="btn btn-primary btn-next">Next</button>
                    </div>
                </div>
            }
        </div>
    </div>
</div>

Answer 1

通过检查 checked attribute behavior for radio button ，我发现您的问题发生是因为 checked 属性是一个 bool 属性，当该属性存在时表示相应的输入元素处于选中状态，无论其值如何 (checked="false" 与 checked="true" 或 checked="checked") 相同。

如果同一组中的多个单选按钮存在 checked 属性，默认情况下它将最后一个单选按钮设置为 checked(请参阅 this fiddle 基于您的原始代码) .因此，当 CompanionReleaseRadio1.Checked 属性设置为 false 时，您需要排除 checked 属性，方法是使用 @functions 内联函数助手，如下例所示:

@functions {
    private object SetRadioButtonChecked(bool isChecked, string RadioID) 
    {
        // checked state from property
        if (isChecked)
        {
            // checked attribute is present
            return new { id = "CompanionReleaseRadio2" + RadioID, @checked = "checked" };
        }
        else
        {
            // checked attribute is not present
            return new { id = "CompanionReleaseRadio2" + RadioID };
        }
    }
}

然后像这样在 RadioButton 帮助程序中调用上面的内联函数:

@foreach (var companionReleases1 in Model.CompanionReleaseRadios1)
{
    <div class="col-sm-4">
        @Html.RadioButtonFor(model => Model.CompanionReleaseRadio1, companionReleases1.RadioID, 
             @SetRadioButtonChecked(companionReleases1.Checked, companionReleases1.RadioID)) 
        <span class="checkbox-label">@companionReleases1.RadioText</span>
    </div>
}

之后，所有 CompanionReleaseRadio1.Checked 属性设置为 false 的单选按钮都应该设置为未选中状态(有关预期结果，请参见 this fiddle)。

引用:

Using @functions in an ASP.NET page with Razor Syntax

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