c# - Radio Button Tag Helpers in ASP.NET 5 MVC 6

Question

I don't see any tag helpers for radio buttons in ASP.NET 5 MVC 6. What's the right way of handling form elements where I need to use radio buttons?

Answer 1

所有输入类型都有一个 TagHelper，其中也包括单选按钮类型。假设您有这样的视图模型

public class CreateUserVm
{
    public string UserName { set; get; }
    public IEnumerable<RoleVm> Roles { set; get; } 
    public int SelectedRole { set; get; }
}
public class RoleVm
{
    public int Id { set; get; }
    public string RoleName { set; get; }        
}

在你的 GET 动作中，

public IActionResult Index()
{
    var vm = new CreateUserVm
    {
        Roles = new List<RoleVm>
        {
            new RoleVm {Id = 1, RoleName = "Admin"},
            new RoleVm {Id = 2, RoleName = "Editor"},
            new RoleVm {Id = 3, RoleName = "Reader"}
        }
    };
    return View(vm);
}

在视图中，您可以简单地为输入标签使用标记。

@model YourNamespaceHere.CreateUserVm
<form asp-action="Index" asp-controller="Home">
    <label class="label">User name</label>
    <div class="col-md-10">
        <input type="text" asp-for="UserName" />
    </div>
    <label class="label">Select a Role</label>
    <div class="col-md-10">
    @foreach (var item in Model.Roles)
    {
       <input asp-for="SelectedRole" type="radio" value="@item.Id" /> @item.RoleName
    }
    </div>
    <input type="submit" />
</form>

当您发布表单时，所选角色的 Rold Id 将在SelectedRole属性中

请记住，上面的剃刀代码将为循环生成的每个输入生成具有相同 Id属性值和属性值的输入元素。name在上面的示例中，它将生成 3 个输入元素（单选按钮类型），其中Id andname属性值设置为SelectedRole。当name属性值与SelectedRole我们的视图模型中的属性名称（

Answer 2

虽然有一些解决方案可供使用asp-for="SomeField"，但我发现最简单的解决方案是将视图模型字段与单选按钮的name字段匹配。

查看型号：

public class MyViewModel
{
   public string MyRadioField { get; set; }
}

表格（为清楚起见没有标签）：

@model MyViewModel
<form asp-action="SomeAction" asp-controller="SomeController">
   <input type="radio" name="MyRadioField" value="option1" checked />
   <input type="radio" name="MyRadioField" value="option2" />
   <input type="radio" name="MyRadioField" value="option3" />

   <input type="submit" />
</form>

提交表单时，MyRadioField将填充选中的单选按钮的值。

Answer 3

我已经编写了自己的标签助手来做到这一点。它用input每个枚举变体的标签和单选按钮替换标签：

using System.Collections.Generic;
using System.Linq;
using System.Text;
using DigitScpi.Web.Helpers;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Razor.TagHelpers;

namespace TagHelpers
{
    /// Generates the radio buttons for an enum. Syntax: `<input radio asp-for="MyMappedEnumField"/>`.
    [HtmlTargetElement("input", Attributes = RadioAttributeName)]
    public class RadioButtonTagHelper : TagHelper
    {
        private const string RadioAttributeName = "radio";
        private const string ForAttributeName = "asp-for";

        [HtmlAttributeNotBound] [ViewContext] public ViewContext ViewContext { get; set; }
        private readonly IHtmlGenerator _generator;

        [HtmlAttributeName(ForAttributeName)] public ModelExpression For { get; set; }
        [HtmlAttributeName(RadioAttributeName)] public bool RadioMarker { get; set; }

        public RadioButtonTagHelper(IHtmlGenerator generator)
        {
            _generator = generator;
        }

        /// <inheritdoc />
        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            output.SuppressOutput();

            foreach (var enumItem in For.Metadata.EnumNamesAndValues)
            {
                var id = VariantId(enumItem);
                var name = For.Metadata.EnumGroupedDisplayNamesAndValues.FirstOrDefault(v => v.Value == enumItem.Value).Key.Name;
                var radio = _generator.GenerateRadioButton(ViewContext, For.ModelExplorer, For.Name, enumItem.Key, false, new {id});
                var label = _generator.GenerateLabel(ViewContext, For.ModelExplorer, For.Name, name, new {@for = id});

                output.PreElement.AppendHtml(radio);
                output.PreElement.AppendHtml(label);
            }
        }

        /// Computes the variant to be unique for each radiobutton.
        private string VariantId(KeyValuePair<string, string> enumItem) =>
            new StringBuilder()
                .Append(ViewContext.CreateUniqueId(_generator.IdAttributeDotReplacement, For.Name))
                .Append(_generator.IdAttributeDotReplacement)
                .Append(enumItem.Key)
                .ToString();
    }
}