System.Web.Mvc.HtmlHelper' does not contain a definition for CheckBox

Question

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Text;
namespace secondMvc.MyControls
{
    public static class CheckBoxList
    {
        public static MvcHtmlString CheckListBox(this HtmlHelper helper, string Name, Dictionary<Int32, string> citiesList, bool IsVertical, string cssClass)
        {
            StringBuilder sb = new StringBuilder();

            sb.Append(string.Format("<div >"));
            foreach (var item in citiesList)
            {


                sb.Append(helper.CheckBox(item.Value, true, new { @class = cssClass, value = item.Key }));
                sb.Append(helper.Label("RadioButtonItems", item.Value));
                sb.Append("&nbsp;");
                if (IsVertical) sb.Append("<br>");

            }
            sb.Append("</div> ");
            return MvcHtmlString.Create(sb.ToString());
        }
    }
}

System.Web.Mvc.HtmlHelper'does not contain a definition forCheckBoxand no extension method'CheckBox'accepting a first argument of type'System.Web.Mvc.HtmlHelper'` could be found (are you missing a using directive or an assembly reference?)

i change web.config like this:

<configuration>

    <appSettings>

    </appSettings>

    <connectionStrings>

    </connectionStrings>
  <pages>
    <namespaces>

      <add namespace="secondMvc.MyControls"/>
    </namespaces>
  </pages>

  <system.web>
    <compilation>
      <assemblies>
      <add assembly="secondMvc.MyControls" />
      </assemblies>
    </compilation>
  </system.web>
</configuration>

but i have same error. any idea?

Answer 1

Add using System.Web.Mvc.Html to your file containing the CheckBoxList static class. It is inside this namespace that extension method such as CheckBox are defined. The web.config namespaces section is completely ignored when compiling C# code. They are used by views. And note that Razor views use the ~/Views/web.config file, not ~/web.config, so make sure you have added the secondMvc.MyControls namespace to the correct web.config if you want your custom extension method to be resolved in views.