HtmlHelper extension method to disable controls and allow for multiple html attributes to be specified

Question

I want to write an extension method that will allow me to disable a control based on a security setting. The code below works and accomplishes what I want. However - because it creates an object that represents all html attributes - I cannot specifiy additional attributes other than the disabled attribute that this code generates.

public static class SecurityHtmlHelper
{
    public static object EnableForPermission(this HtmlHelper html, Permission permission)
    {
        if (Security.HasPermission(permission))
            return new object();
        else
            return new { disabled = "disabled" };
    }
}

Example of how the above is used:

  @Html.ActionLink("permission test", "/", null, @Html.EnableForPermission(Permission.PM_PROCEDURE_ALT_SCEN_READ))

Desired usage example (does not build):

  @Html.ActionLink("permission test", "/", null, new { @style ="xyz", @Html.EnableForPermission(Permission.PM_PROCEDURE_ALT_SCEN_READ)})

No I dont want to use javascript and yes I realize disabling a link does not prevent the user from navigating to a page there are other controls in place for that.

Thx.

For reference on disabled attribute: Correct value for disabled attribute

`disabled` is not a valid attribute for an `` tag! What are you expecting it to do? — , Feb 28 '15 at 01:08
indeed it is not (although it works :)). I will use the extension method on various controls, I badly chose as an example. — , Feb 28 '15 at 01:16
It would not work on a `` tag (except to generate invalid html). In the case in your question just do `@if (Security.HasPermission(Permission.PM_PROCEDURE_ALT_SCEN_READ)) { @Html.ActionLink(...) }` but you could create a html helper that that either returns an action link or null. — , Feb 28 '15 at 01:20
I am hoping for something more elegant (read shorter) than that. There are hundreds of controls I need to use this on. Also, I almost always want to render the control, but in a disabled state if permissions dont allow. thx. — , Feb 28 '15 at 01:37
Then you would need to create custom html helpers for each control (and potentially for each overload). In any case it would be simpler if you had a view model or `ViewBag` property (say `bool HasPermission`) to simplify the `if` blocks. And I assume you understand that disabled controls do not post back so their properties will be `null` and if they have any validation attributes, `ModelState` will be invalid. — , Feb 28 '15 at 01:42
Your points are well made, unfortunately I have to render the controls as disabled per client requirement. Just hoping for a cleaner shorter syntax than big if blocks. — , Feb 28 '15 at 01:57
You can always create a helper that merges html attributes and adds the `disabled` attribute based on the permission something liks `@Html.TextBoxFor(m => m.SomeProperty, Html.EnablePermissionsFor(Permission.PM_PROCEDURE_ALT_SCEN_READ, new { @class = "myClass" }))`. Can give you an example if you want. — , Feb 28 '15 at 02:03
Yes please provide an example. Your comment appears to be what I am trying to do. If it dosnt work on tags thats just the way it is. Most of what I need to use it on is inputs. — , Feb 28 '15 at 02:09

score 1 · Accepted Answer · 2015-02-28T02:52:47.963

A disabled attribute wont work on an <a> tag (and its invalid html), but from your comments, you want to use the helper to apply it to controls anyway.

I'm not sure what Security.HasPermission(permission) does, but if its calling a service, then it does not belong in a helper. In any case I suggest you pass a boolean value to the view indicating if the permission applies, using a view model or ViewBag property, for example in the controller

ViewBag.HasPermission = Security.HasPermission(Permission.PM_PROCEDURE_ALT_SCEN_READ);

The helper needs to merge the html attributes you pass to it with the disabled attribute if applicable

public static IDictionary<string, object> EnableForPermission(object htmlAttributes, bool hasPermission)
{
  IDictionary<string, object> attributes = HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes);
  if (!hasPermission)
  {
    attributes.Add("disabled", "disabled");
  }
  return attributes;
}

and then in the view

@Html.TextBoxFor(m => m.someProperty, EnableForPermission(new { @class = "someClass" }, ViewBag.HasPermission))

HtmlHelper extension method to disable controls and allow for multiple html attributes to be specified

1 Answers1