从CheckboxList获取逗号分隔的字符串HTML助手

Question

我从互联网获得了以下代码，用于CheckboxListFor html助手扩展。目前，在SelectedValues中，它将从复选框列表中返回选定值的List<string>。我想在SelectedValues中得到一个逗号分隔的字符串。

任何人都可以告诉我如何实现它吗？

下面是代码：

的HtmlHelper扩展：

 /// <summary> 
    /// Returns a checkbox for each of the provided <paramref name="items"/>. 
    /// </summary> 
    public static MvcHtmlString CheckBoxList(this HtmlHelper htmlHelper, string listName, IEnumerable<SelectListItem> items, object htmlAttributes = null) 
    { 
     var container = new TagBuilder("div"); 
     foreach (var item in items) 
     { 
      var label = new TagBuilder("label"); 
      label.MergeAttributes(new RouteValueDictionary(htmlAttributes), true); 

      var cb = new TagBuilder("input"); 
      cb.MergeAttribute("type", "checkbox"); 
      cb.MergeAttribute("name", listName); 
      cb.MergeAttribute("value", item.Value ?? item.Text); 
      if (item.Selected) 
       cb.MergeAttribute("checked", "checked"); 

      label.InnerHtml = cb.ToString(TagRenderMode.SelfClosing) + item.Text; 

      container.InnerHtml += label.ToString(); 
     } 

     return new MvcHtmlString(container.ToString()); 
    } 

    private static IEnumerable<SelectListItem> GetCheckboxListWithDefaultValues(object defaultValues, IEnumerable<SelectListItem> selectList) 
    { 
     var defaultValuesList = defaultValues as IEnumerable; 

     if (defaultValuesList == null) 
      return selectList; 

     IEnumerable<string> values = from object value in defaultValuesList 
            select Convert.ToString(value, CultureInfo.CurrentCulture); 

     var selectedValues = new HashSet<string>(values, StringComparer.OrdinalIgnoreCase); 
     var newSelectList = new List<SelectListItem>(); 

     selectList.ForEach(item => 
     { 
      item.Selected = (item.Value != null) ? selectedValues.Contains(item.Value) : selectedValues.Contains(item.Text); 
      newSelectList.Add(item); 
     }); 

     return newSelectList; 
    } 

    /// <summary> 
    /// Returns a checkbox for each of the provided <paramref name="items"/>. 
    /// </summary> 
    public static MvcHtmlString CheckBoxListFor<TModel, TValue>(this HtmlHelper<TModel> htmlHelper, 
     Expression<Func<TModel, TValue>> expression, 
     IEnumerable<SelectListItem> items, object htmlAttributes = null) 
    { 
     var listName = ExpressionHelper.GetExpressionText(expression); 
     var metaData = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData); 

     items = GetCheckboxListWithDefaultValues(metaData.Model, items); 
     return htmlHelper.CheckBoxList(listName, items, htmlAttributes); 
    } 

在视图：

@Html.CheckBoxListFor(model => model.SelectedValues, Model.MySelectList) 

型号：

public class MyViewModel 
{   
     public SelectList MySelectList{ get; set; } 

     public List<string> SelectedValues{ get; set; } 

     //public string SelectedValues{ get; set; } Can I get comma separated string here 
} 

请注意，我需要逗号小号在控制器操作返回列表之后，从帮助程序返回的字符串没有被分离出来。

为什么我试图做到这一点？：

//Here in my model, I am getting `SelectedValues` which is a List<String>. 
public ActionResult Index(MyViewModel model) 
{ 
     //My code.... 
} 

在查看

//But I cannot save this list into RouteValueDictionary like: 
var searchCriteria = new RouteValueDictionary(); 
searchCriteria["model.SelectedValues"] = Model.SelectedValues; // List<string> cannot be save here. That's why I needed comma separated string. 
var viewDataDictionary = new ViewDataDictionary(); 
viewDataDictionary["searchCriteria"] = searchCriteria; 

@Html.Partial("_MyPagingView", Model.MyList, viewDataDictionary) 

有哪些要求Index的动作，当下一页是_MyPagingView内部的整个机制点击。为了保持搜索状态，我们需要将搜索到的数据保存在RouteValueDictionary之内。

Answer 1

您可以创建一个辅助方法的SelectedValues添加到RouteValueDictionary

public void AddRoutes(List<string> values, string propertyName, RouteValueDictionary dictionary) 
{ 
    for (int i = 0; i < values.Count; i++) 
    { 
     string key = string.Format("{0}[{1}]", propertyName, i); 
     dictionary[key] = values[i]; 
    } 
} 

，然后用它作为

var searchCriteria = new RouteValueDictionary(); 
AddRoutes(Model.SelectedValues, "SelectedValues", searchCriteria); 

，避免需要创建一个隐藏的输入，并使用JavaScript

Answer 2

我更喜欢更改您的视图模型的代码：

public class MyViewModel 
{ 
    public SelectList MySelectList{ get; set; } 

    public List<string> SelectedValues { get; set; } 

    public string SelectedString 
    { 
     get 
     { 
      if (SelectedValues == null) return ""; 
      return string.Join(",", SelectedValues); 
     } 
     set 
     { 
      if (!string.IsNullOrEmpty(value)) 
      { 
       SelectedValues = value.Split(',').ToList(); 
      } 
     } 
    } 
} 

你可以得到逗号分隔字符串：

//In controller 
var selected = model.SelectedString; 

//In view 
searchCriteria["model.SelectedValues"] = Model.SelectedString;