ASP.NET MVC 中使用“RadioButtonList”和“CheckBoxList”

一、有何特别之处？

和我的很多文章一样，旨在提供一种大体的解决方案，本解决方案旨在解决如下一些问题：

• 通过独立的组件对绑定到ListControl（ASP.NET Web Form的说法）的列表进行单独管理；
• 自动地调用上面这个组件获取列表信息进行相关Html的生成；
• 支持ASP.NET MVC原生的Model Binding。

二、实例演示

下面是代表个人信息同时作为Model的Person类型，Gender、MaritalStatus 和Country分别代表性别、婚姻状况和国籍（这里支持多国籍）。

public class Person
{
    public string Name { get; set; }
     public string Gender { get; set; }
     [Display(Name = "Marital Status")]
     public string MaritalStatus { get; set; }
     public string[] Country { get; set; }
}

　　

上述三个属性分别代表CodeManager这个独立组件维护的三个列表，CodeManager和代表列表选项的CodeDescription定义如下：

public class CodeDescription
  {
      public string Code { get; set; }
      public string Description { get; set; }
      public string Category{get;set;}
   
     public CodeDescription(string code, string description, string category)
      {
          this.Code = code;
          this.Description = description;
          this.Category = category;
      }
  }
  public static class CodeManager
  {
      private static CodeDescription[] codes = new CodeDescription[]
      {
          new CodeDescription("M","Male","Gender"),
          new CodeDescription("F","Female","Gender"),
          new CodeDescription("S","Single","MaritalStatus"),
          new CodeDescription("M","Married","MaritalStatus"),
          new CodeDescription("CN","China","Country"),
          new CodeDescription("US","Unite States","Country"),
          new CodeDescription("UK","Britain","Country"),
          new CodeDescription("SG","Singapore","Country")
     };
    public static Collection<CodeDescription> GetCodes(string category)
     {
         Collection<CodeDescription> codeCollection = new Collection<CodeDescription>();
         foreach(var code in codes.Where(code=>code.Category == category))
        {
            codeCollection.Add(code);
         }
         return codeCollection;
     }
 }

　　

在默认的HomeController中，我们定义了如下两个Index方法，它们分别用于测试出栈数据（Model->UI)入栈数据（UI-〉Model）的绑定。

public class HomeController : Controller
{
    public ActionResult Index()
    {
        return View(new Person { Name = "Foo", Gender = "M", MaritalStatus = "S", Country = new string[]{"CN","US"} });
    }
    [HttpPost]
    public ActionResult Index(Person person)
    {
        return this.View(person);
    }
}

下面是Index操作对应的View的定义，这是一个Model类型为Person的强类型View。对于Person的三个基于列表的属性，我们分别调用了自定义的扩展方法RadioButtonListFor和CheckBoxListFor进行了绑定。方法的最后两个参数分别代表通过CodeManager维护的列表的组别（Gender、MaritalStatus和Country），和同组RadioButton和CheckBox布局方向（水平或者纵向）。

@using System.Web.UI.WebControls
@model Person
@{
    ViewBag.Title = "Index";
}
@using (Html.BeginForm())
{
    <table id="container">
        <tr>
            <td class="label">@Html.LabelFor(m => m.Name):</td>
            <td>@Html.EditorFor(m => m.Name)</td>
        </tr>
         <tr>
            <td class="label">@Html.LabelFor(m => m.Gender):</td>
            <td>@Html.RadioButtonListFor(m => m.Gender, "Gender")</td>
        </tr>
         <tr>
            <td class="label">@Html.LabelFor(m => m.MaritalStatus):</td>
            <td>@Html.RadioButtonListFor(m => m.MaritalStatus, "MaritalStatus")</td>
        </tr>
         <tr>
            <td class="label">@Html.LabelFor(m => m.Country):</td>
            <td>@Html.CheckBoxListFor(m => m.Country, "Country", RepeatDirection.Vertical)</td>
        </tr>
        <tr>
            <td colspan="2"><input type="submit" value="Save" /></td>
        </tr>
    </table>
}

下面是最终呈现出来的效果：

三、两组扩展方法具体实现

现在我们简单地来看看RadioButtonList/RadioButtonListFor和CheckBoxList/CheckBoxListFor这两组扩展方法的实现。我们通过CodeManager得到列表集合，通过HtmlHelper结合 ModelMetadata得到当前数据，最终借助于ListControlUtil的GenerateHtml生成相关的Html。

public static class ListControlExtensions
{
    public static MvcHtmlString RadioButtonList(this HtmlHelper htmlHelper, string name, string codeCategory, RepeatDirection repeatDirection = RepeatDirection.Horizontal)
    {
        var codes = CodeManager.GetCodes(codeCategory);
        return ListControlUtil.GenerateHtml(name, codes, repeatDirection,"radio",null);
    }
    public static MvcHtmlString RadioButtonListFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, string codeCategory, RepeatDirection repeatDirection = RepeatDirection.Horizontal)
    {
        var codes = CodeManager.GetCodes(codeCategory);
        ModelMetadata metadata = ModelMetadata.FromLambdaExpression<TModel, TProperty>(expression, htmlHelper.ViewData);
        string name = ExpressionHelper.GetExpressionText(expression);
        string fullHtmlFieldName = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(name);
        return ListControlUtil.GenerateHtml(fullHtmlFieldName, codes, repeatDirection, "radio", metadata.Model);
    }

    public static MvcHtmlString CheckBoxList(this HtmlHelper htmlHelper, string name, string codeCategory, RepeatDirection repeatDirection = RepeatDirection.Horizontal)
    {
        var codes = CodeManager.GetCodes(codeCategory);
        return ListControlUtil.GenerateHtml(name, codes, repeatDirection, "checkbox", null);
    }
    public static MvcHtmlString CheckBoxListFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, string codeCategory, RepeatDirection repeatDirection = RepeatDirection.Horizontal)
    {
        var codes = CodeManager.GetCodes(codeCategory);
        ModelMetadata metadata = ModelMetadata.FromLambdaExpression<TModel, TProperty>(expression, htmlHelper.ViewData);
        string name = ExpressionHelper.GetExpressionText(expression);
        string fullHtmlFieldName = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(name);
        return ListControlUtil.GenerateHtml(fullHtmlFieldName, codes, repeatDirection, "checkbox", metadata.Model);
    }
}

ListControlUtil中生成相关Html的逻辑定义如下：

public static class ListControlUtil
{
    public static MvcHtmlString GenerateHtml(string name, Collection<CodeDescription> codes, RepeatDirection repeatDirection, string type, object stateValue)
    {
        TagBuilder table = new TagBuilder("table");
        int i = 0;
        bool isCheckBox = type == "checkbox";
        if (repeatDirection == RepeatDirection.Horizontal)
        {
            TagBuilder tr = new TagBuilder("tr");
            foreach (var code in codes)
            {
                i++;
                string id = string.Format("{0}_{1}", name, i);
                TagBuilder td = new TagBuilder("td");

                bool isChecked = false;
                if (isCheckBox)
                {
                    IEnumerable<string> currentValues = stateValue as IEnumerable<string>;
                    isChecked = (null != currentValues && currentValues.Contains(code.Code));
                }
                else
                {
                    string currentValue = stateValue as string;
                    isChecked = (null != currentValue && code.Code == currentValue);
                }

                td.InnerHtml = GenerateRadioHtml(name, id, code.Description, code.Code, isChecked,type);
                tr.InnerHtml += td.ToString();
            }
            table.InnerHtml = tr.ToString();
        }
        else
        {
            foreach (var code in codes)
            {
                TagBuilder tr = new TagBuilder("tr");
                i++;
                string id = string.Format("{0}_{1}", name, i);
                TagBuilder td = new TagBuilder("td");

                bool isChecked = false;
                if (isCheckBox)
                {
                    IEnumerable<string> currentValues = stateValue as IEnumerable<string>;
                    isChecked = (null != currentValues && currentValues.Contains(code.Code));
                }
                else
                {
                    string currentValue = stateValue as string;
                    isChecked = (null != currentValue && code.Code == currentValue);
                }

                td.InnerHtml = GenerateRadioHtml(name, id, code.Description, code.Code, isChecked, type);
                tr.InnerHtml = td.ToString();
                table.InnerHtml += tr.ToString();
            }
        }
        return new MvcHtmlString(table.ToString());
    }

    private static string GenerateRadioHtml(string name, string id, string labelText, string value, bool isChecked, string type)
    {
        StringBuilder sb = new StringBuilder();

        TagBuilder label = new TagBuilder("label");
        label.MergeAttribute("for", id);
        label.SetInnerText(labelText);

        TagBuilder input = new TagBuilder("input");
        input.GenerateId(id);
        input.MergeAttribute("name", name);
        input.MergeAttribute("type", type);
        input.MergeAttribute("value", value);
        if (isChecked)
        {
            input.MergeAttribute("checked", "checked");
        }
        sb.AppendLine(input.ToString());
        sb.AppendLine(label.ToString());
        return sb.ToString();
    }
}

通过对HtmlHelper扩展简化“列表控件”的绑定 
为HtmlHelper添加一个RadioButtonList扩展方法 
在ASP.NET MVC中使用“RadioButtonList”和“CheckBoxList”