原文:

通过扩展方法，可以让CheckBox水平排列，生成CheckBoxList，正如""一文。但，如何对生成的CheckBoxList验证呢？比如要求至少勾选一项：

 

□ 思路

在强类型视图页中，@Html.EditorFor(model => model.属性, "模版名称", new{ ...路由数据...})，模版名称对应Views/Shared/EditorTemplates/CheckBoxList.cshtml部分视图，路由数据用来传递生成CheckBoxList所需要的一切，并在CheckBoxList.cshtml中显示错误信息，最后CheckBoxList的生成交给扩展方法。

□ Model

    public class Course

    {

        public int Id { get; set; }

        public string Name { get; set; }

    }

using System.ComponentModel.DataAnnotations;

namespace MvcApplication1.Models

{

    public class Student

    {

        [Display(Name = "姓名")]

        [Required(ErrorMessage = "必填")]

        [StringLength(100, ErrorMessage = "最大长度100")]

        public string Name { get; set; }

        [Display(Name = "所选课程")]

        [Required(ErrorMessage = "至少选择一个课程")]

        public string Courses{ get; set; }

    }

}

 

□ 在_Layout.cshtml中启用客户端异步验证

    @Scripts.Render("~/bundles/jquery")

    @Scripts.Render("/bundles/jqueryval") //启用客户端异步验证

    @RenderSection("scripts", required: false)

 

□ Home/Index.cshtml

@using MvcApplication1.Infrastructure.Enums

@model MvcApplication1.Models.Student

@{

ViewBag.Title = "Index";

Layout = "~/Views/Shared/_Layout.cshtml";

}

@using (Html.BeginForm())

{

@Html.AntiForgeryToken()

@Html.ValidationSummary(true)

Student

@Html.LabelFor(model => model.Name)

@Html.EditorFor(model => model.Name)

@Html.ValidationMessageFor(model => model.Name)

@Html.LabelFor(model => model.Courses)

@Html.EditorFor(model => model.Courses, "CheckBoxList", new

{

TagName = "Courses",

CheckBoxItems = ViewBag.Course,

Position = Position.Horizontal,

Numbers = 3

})

}

其中，用到了有关CheckBoxList水平或垂直排列的一个枚举：

namespace MvcApplication1.Infrastructure.Enums

{

    public enum Position

    {

        Horizontal,

        Vertical

    }

}  

生成CheckBoxList的路由数据，以及模版名称：

            @Html.EditorFor(model => model.Courses, "CheckBoxList", new

            {

                TagName = "Courses",

                CheckBoxItems = ViewBag.Course,

                Position = Position.Horizontal,

                Numbers = 3

            })

 

□ Views/Shared/EditorTemplates/CheckBoxList.cshtml

@using MvcApplication1.Infrastructure.Enums

@{

var required = false;

object validationMessage = string.Empty;

//获取客户端验证属性

var validationAttributes = Html.GetUnobtrusiveValidationAttributes("");

if (validationAttributes.ContainsKey("data-val") && validationAttributes.ContainsKey("data-val-required"))

{

required = true;

if (!validationAttributes.TryGetValue("data-val-required", out validationMessage))

{

validationMessage = "This field is required.";

}

validationAttributes.Add("required","required");

}

var tagName = ViewData["TagName"] == null ? "CheckBoxList" : (string)ViewData["TagName"];

var checkboxItems = ViewData["CheckBoxItems"] == null ? new List
     
      () : (IEnumerable
      
       )ViewData["CheckBoxItems"];
      
     

var position = ViewData["Position"] == null ? Position.Horizontal : (Position)ViewData["Position"];

var numbers = 0;

if (ViewData["Numbers"] == null)

{

numbers = 1;

}

else if (!int.TryParse(ViewData["Numbers"].ToString(), out numbers))

{

numbers = 1;

}

else

{

numbers = (int)ViewData["Numbers"];

}

}

@Html.CheckBoxList(

tagName,

checkboxItems,

new RouteValueDictionary(validationAttributes),

position,

numbers)

@if (required)

{

@validationMessage

}

 

□ 生成CheckBoxList的扩展方法

using System.Collections.Generic;

using System.Linq;

using System.Text;

using MvcApplication1.Infrastructure.Enums;

namespace System.Web.Mvc

{

public static class CheckBoxListExtensions

{

#region 水平方向

/// 

/// CheckBoxList

/// 

/// HTML helper

/// 

/// 

/// 

/// 每行显式的个数

/// 
     

public static MvcHtmlString CheckBoxList(this HtmlHelper htmlHelper,

string name,

IEnumerable
     
       listInfo,
     

IDictionary
     
       htmlAttributes,
     

int number)

{

if (string.IsNullOrEmpty(name))

{

throw new ArgumentException("必须给CheckBoxList一个name值", "name");

}

if (listInfo == null)

{

throw new ArgumentNullException("listInfo", "List
     
       listInfo不能为null");
     

}

var selectListItems = listInfo as SelectListItem[] ?? listInfo.ToArray();

if (!selectListItems.Any())

{

throw new ArgumentException("List
     
       listInfo 至少有一组资料", "listInfo");
     

}

var sb = new StringBuilder();

var lineNumber = 0;

foreach (var info in selectListItems)

{

lineNumber++;

var builder = new TagBuilder("input");

if (info.Selected)

{

builder.MergeAttribute("checked", "checked");

}

builder.MergeAttributes(htmlAttributes);

builder.MergeAttribute("type", "checkbox");

builder.MergeAttribute("value", info.Value);

builder.MergeAttribute("name", name);

builder.MergeAttribute("id", string.Format("{0}_{1}", name, info.Value));

sb.Append(builder.ToString(TagRenderMode.Normal));

var labelBuilder = new TagBuilder("label");

labelBuilder.MergeAttribute("for", string.Format("{0}_{1}", name, info.Value));

labelBuilder.InnerHtml = info.Text;

sb.Append(labelBuilder.ToString(TagRenderMode.Normal));

if (number == 0 || (lineNumber % number == 0))

{

sb.Append("
");

}

}

return MvcHtmlString.Create(sb.ToString());

}

public static MvcHtmlString CheckBoxList(this HtmlHelper htmlHelper,

string name,

IEnumerable
     
       listInfo)
     

{

return htmlHelper.CheckBoxList(name, listInfo, (IDictionary
     
      ) null, 0);
     

}

#endregion

#region 垂直方向

public static MvcHtmlString CheckBoxListVertical(this HtmlHelper htmlHelper,

string name,

IEnumerable
     
       listInfo,
     

IDictionary
     
       htmlAttributes,
     

int columnNumber = 1)

{

if (string.IsNullOrEmpty(name))

{

throw new ArgumentException("必须给CheckBoxList的name属性赋值", "name");

}

if (listInfo == null)

{

throw new ArgumentNullException("listInfo", "List
     
       listInfo不能为null");
     

}

var selectListItmes = listInfo as SelectListItem[] ?? listInfo.ToArray();

if (!selectListItmes.Any())

{

throw new ArgumentException("List
     
       listInfo不能为null","listInfo");
     

}

var dataCount = selectListItmes.Count();

var rows = Convert.ToInt32(Math.Ceiling(Convert.ToDecimal(dataCount)/Convert.ToDecimal(columnNumber)));

if (dataCount <= columnNumber || dataCount - columnNumber == 1)

{

rows = dataCount;

}

var wrapBuilder = new TagBuilder("div");

wrapBuilder.MergeAttribute("style","float:left; line-height:25px; padding-right:5px;");

var wrapStart = wrapBuilder.ToString(TagRenderMode.StartTag);

var wrapClose = string.Concat(wrapBuilder.ToString(TagRenderMode.EndTag),

" 
     
");

var wrapBreak = string.Concat("", wrapBuilder.ToString(TagRenderMode.StartTag));

var sb = new StringBuilder();

sb.Append(wrapStart);

var lineNumber = 0;

foreach (var info in selectListItmes)

{

var builder = new TagBuilder("input");

if (info.Selected)

{

builder.MergeAttribute("checked","checked");

}

builder.MergeAttributes(htmlAttributes);

builder.MergeAttribute("type","checkbox");

builder.MergeAttribute("value", info.Value);

builder.MergeAttribute("name", name);

builder.MergeAttribute("id", string.Format("{0}_{1}",name, info.Value));

sb.Append(builder.ToString(TagRenderMode.Normal));

var labelBuilder = new TagBuilder("label");

labelBuilder.MergeAttribute("for", string.Format("{0}_{1}", name, info.Value));

labelBuilder.InnerHtml = info.Text;

sb.Append(labelBuilder.ToString(TagRenderMode.Normal));

lineNumber++;

if (lineNumber.Equals(rows))

{

sb.Append(wrapBreak);

lineNumber = 0;

}

else

{

sb.Append("
");

}

}

sb.Append(wrapClose);

return MvcHtmlString.Create(sb.ToString());

}

#endregion

#region 水平或垂直方向

public static MvcHtmlString CheckBoxList(this HtmlHelper htmlHelper,

string name,

IEnumerable
     
       listInfo,
     

IDictionary
     
       htmlAttributes,
     

Position position = Position.Horizontal,

int number = 0)

{

if (string.IsNullOrEmpty(name))

{

throw new ArgumentException("必须给CheckBoxList的name属性赋值","name");

}

if (listInfo == null)

{

throw new ArgumentNullException("listInfo", "List
     
       listInfo不能为null");
     

}

var selectListItems = listInfo as SelectListItem[] ?? listInfo.ToArray();

if (!selectListItems.Any())

{

throw new ArgumentException("List
     
       listInfo至少要一组资料","listInfo");
     

}

var sb = new StringBuilder();

var lineNumber = 0;

switch (position)

{

case Position.Horizontal:

foreach (var info in selectListItems)

{

lineNumber++;

sb.Append(CreateCheckBoxItem(info, name, htmlAttributes));

if (number == 0 || (lineNumber%number == 0))

{

sb.Append("
");

}

}

sb.Append("
");

break;

case Position.Vertical:

var dataCount = selectListItems.Count();

var rows = Convert.ToInt32(Math.Ceiling(Convert.ToDecimal(dataCount)/Convert.ToDecimal(number)));

if (dataCount <= number || dataCount - number == 1)

{

rows = dataCount;

}

var wrapBuilder = new TagBuilder("div");

wrapBuilder.MergeAttribute("style","float:left; line-height:25px; padding-right:5px;");

var wrapStart = wrapBuilder.ToString(TagRenderMode.StartTag);

var wrapClose = string.Concat(wrapBuilder.ToString(TagRenderMode.EndTag), " 
     
");

var wrapBreak = string.Concat("", wrapBuilder.ToString(TagRenderMode.StartTag));

sb.Append(wrapStart);

foreach (var info in selectListItems)

{

lineNumber++;

sb.Append(CreateCheckBoxItem(info, name, htmlAttributes));

if (lineNumber.Equals(rows))

{

sb.Append(wrapBreak);

lineNumber = 0;

}

else

{

sb.Append(wrapClose);

}

}

sb.Append(wrapClose);

break;

}

return MvcHtmlString.Create(sb.ToString());

}

internal static string CreateCheckBoxItem(SelectListItem info, string name,

IDictionary
     
       htmlAttributes)
     

{

var sb = new StringBuilder();

var builder = new TagBuilder("input");

if (info.Selected)

{

builder.MergeAttribute("checked","checked");

}

builder.MergeAttributes(htmlAttributes);

builder.MergeAttribute("type", "checkbox");

builder.MergeAttribute("value", info.Value);

builder.MergeAttribute("name", name);

builder.MergeAttribute("id", string.Format("{0}_{1}", name, info.Value));

sb.Append(builder.ToString(TagRenderMode.Normal));

var labelBuilder = new TagBuilder("label");

labelBuilder.MergeAttribute("for", string.Format("{0}_{1}", name, info.Value));

labelBuilder.InnerHtml = info.Text;

sb.Append(labelBuilder.ToString(TagRenderMode.Normal));

return sb.ToString();

}

#endregion

}

}

 

□ HomeController

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.Mvc;

using MvcApplication1.Infrastructure.Services;

using MvcApplication1.Models;

namespace MvcApplication1.Controllers

{

public class HomeController : Controller

{

private readonly  CourseService service = new CourseService();

private List
     
       coursesSelectListItems
     

{

get

{

var courses = this.service.GetCourses();

var items = new List
     
      ();
     

foreach (var c in courses)

{

items.Add(new SelectListItem()

{

Value = c.Id.ToString(),

Text = c.Name

});

}

return items;

}

}

public ActionResult Index()

{

ViewBag.Course = this.coursesSelectListItems;

return View();

}

[HttpPost]

[ValidateAntiForgeryToken]

public ActionResult Index(Student stu)

{

ViewBag.Course = this.coursesSelectListItems;

if (ModelState.IsValid)

{

return View();

}

return View(stu);

}

}

}

 

□ CouseService.cs

using System.Collections.Generic;

using MvcApplication1.Models;

namespace MvcApplication1.Infrastructure.Services

{

public class CourseService

{

public IEnumerable
     
       GetCourses()
     

{

return new List
     
      ()
     

{

new Course(){Id = 1, Name = "语文"},

new Course(){Id = 2, Name = "数学"},

new Course(){Id = 3, Name = "哲学"},

new Course(){Id = 4, Name = "英语"},

new Course(){Id = 5,Name = "法语"},

new Course(){Id = 6, Name = "物理"},

new Course(){Id = 7, Name = "化学"},

new Course(){Id = 8, Name = "工程"}

};

}

}

}

参考资料：