从CheckboxList HTML Helper获取以逗号分隔的字符串 [英] Get comma-separated string from CheckboxList HTML Helper

问题描述

我从Internet上获得了CheckboxListFor html helper扩展的以下代码.目前，它在SelectedValues中从复选框列表中返回所选值的List<string>.我想在SelectedValues中获取一个逗号分隔的字符串.

I got the following code from the internet for CheckboxListFor html helper extension. At the moment, in the SelectedValues it is returning a List<string> of selected values from the checkboxlist. I want to get a comma-separated string in SelectedValues.

有人可以告诉我我如何实现吗?

Can anyone tell me how I can achieve it?

这是代码:

HTMLHelper扩展名:

HTMLHelper extension:

        /// <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);
    }

在视图中:

@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，我需要从帮助程序返回的逗号分隔的字符串，而不是在获得控制器动作的列表之后.

为什么要尝试执行此操作?:

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

可见

//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)

_MyPagingView内部有一个完整的机制，每当单击下一页时，该机制就会调用Index Action.为了保持搜索状态，我们需要将搜索到的数据保留在RouteValueDictionary中.

There is a whole mechanism inside the _MyPagingView which calls Index Action whenever next page is clicked. And to preserve the state of the search we need to keep our searched data inside RouteValueDictionary.

推荐答案

您可以创建一个辅助方法以将SelectedValues添加到a RouteValueDictionary

You could create a helper method to add theSelectedValues to aRouteValueDictionary

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];
    }
}

，然后将其用作

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

并避免需要创建隐藏的输入并使用javascript

and avoid the need to create a hidden input and use javascript

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