Using preview 4 of ASP.NET MVC Code like:

<%= Html.CheckBox( "myCheckBox", "Click Here", "True", false ) %>

only outputs:

<input type="checkbox"  value="True"  name="myCheckBox"  />

There is a name there for the form post back but no id for javascript or labels :-(

I was hoping that changing it to:

Html.CheckBox( "myCheckBox", "Click Here", 
               "True", false, new { id="myCheckBox" } )

would work - but instead I get an exception:

System.ArgumentException: An item with the same key has already been added.

As if there was already an id somewhere in a collection somewhere - I'm stumped!

The full exception for anyone interested follows (hey - wouldn't it be nice to attach files in here):

System.ArgumentException: An item with the same key has already been added. 
   at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at System.Web.Routing.RouteValueDictionary.Add(String key, Object value)
   at System.Web.Mvc.TagBuilder2.CreateInputTag(HtmlInputType inputType, String name, RouteValueDictionary attributes)
   at System.Web.Mvc.CheckBoxBuilder.CheckBox(String htmlName, RouteValueDictionary htmlAttributes)
   at System.Web.Mvc.CheckBoxBuilder.CheckBox(String htmlName, String text, String value, Boolean isChecked, RouteValueDictionary htmlAttributes)
   at System.Web.Mvc.CheckBoxExtensions.CheckBox(HtmlHelper helper, String htmlName, String text, String value, Boolean isChecked, Object htmlAttributes)
   at ASP.views_account_termsandconditions_ascx.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in c:\dev\myProject\Views\Account\Edit.ascx:line 108

Apparently this is a bug. Because they are adding it to potential rendering values, they just forgot to include it. I would recommend creating a bug on codeplex, and download the source and modify it for your needs.

Nick Berardi
+3  A: 

Try this:

<%= Html.CheckBox("myCheckbox", "Click here", "True", false, new {_id ="test" })%>

For any keyword you can use an underscore before the name of the attribute. Instead of class you use _class. Since class is a keyword in C#, and also the name of the attribute in HTML. Now, "id" isn't a keyword in C#, but perhaps it is in another .NET language that they want to support. From what I can tell, it's not a keyword in VB.NET, F#, or Ruby so maybe it is a mistake that they force you to use an underscore with it.

Lance Fisher
where is this decribed in documentation?
Jeff Martin
I don't know if it in the documentation. I couldn't find it. I think I just read it on Phil Haacks's blog. Also, I think the prefix was changed to an @ from an underscore, so try "new [email protected]="test"} if the above doesn't work.
Lance Fisher