当checked属性为false时，单选按钮默认被选中？

我正在尝试生成单选按钮，有条件地检查检查的属性，如果该值存在于数据库中，则应选择它，否则检查的属性为 false。所以最初数据库中没有行，所有单选按钮的检查属性也为 false，但仍然在 UI 上选择，请参见下图

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

视图模型

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; }
}

View

@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>

通过检查checked单选按钮的属性行为 https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/radio#checked，我发现你的问题出现是因为checkedattribute 是一个布尔属性，当该属性存在时，指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" or checked="checked").

If checked属性存在于同一组中的多个单选按钮，默认情况下它将最后一个单选按钮设置为checked (see 这把小提琴 https://dotnetfiddle.net/4MTE7w基于您的原始代码）。因此，您需要排除checked属性时CompanionReleaseRadio1.Checked属性设置为 false 通过利用@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 };
        }
    }
}

然后在里面调用上面的内联函数RadioButton像这样的助手：

@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，所有单选按钮都带有CompanionReleaseRadio1.Checked属性设置为false应该设置为未选中状态（参见这把小提琴 https://dotnetfiddle.net/7jDes8达到预期的结果）。

参考：

通过 Razor 语法在 ASP.NET 页面中使用 @functions https://blogs.msdn.microsoft.com/timlee/2010/07/30/using-functions-in-an-asp-net-page-with-razor-syntax/

相关问题：

如何在cshtml模板中创建函数？ https://stackoverflow.com/questions/6531983/how-to-create-a-function-in-a-cshtml-template

asp.net mvc3 基于模型检查单选按钮 https://stackoverflow.com/questions/8111942/asp-net-mvc3-checking-radio-button-based-on-model