asp.net mvc html extension for adding an attribute to an editor

htmlextensions.cs

public static IHtmlString ReadOnlyEditorFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, object
htmlAttributes = null, bool isReadOnly = false)
{
    IDictionary<string, object> attributes = HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes);
    if (isReadOnly)
    {
        attributes.Add("readonly", "readonly");
    }

    return html.EditorFor(expression, new { htmlAttributes = attributes });
}

model.cs

[Display(Name = "Event Date")]
[DataType(DataType.Date)]
[DisplayFormat(DataFormatString = "{0:MM-dd-yyyy}", ApplyFormatInEditMode = true)]
[Range(typeof(DateTime), "01-01-2010", "12-31-2030")]
public DateTime? EventDate { get; set; }

output.html

<div class="row">
    <div class="col-xs-3">
        <input class="form-control input-lg text-box single-line" data-val="true" data-val-date="The field Event Date must be a date." data-val-range="The field Event Date must be between 1/1/2010 12:00:00 AM and 12/31/2030 12:00:00 AM." data-val-range-max="12/31/2030 00:00:00" data-val-range-min="01/01/2010 00:00:00" id="EventDate" name="EventDate" type="date" value="08-01-2015" />
    </div>
</div>
<div class="row">
    <div class="col-xs-3">
        <input class="form-control input-lg text-box single-line" id="EventDate" name="EventDate" type="date" value="08-01-2015" />
    </div>
</div>

razor.cshtml

<div class="row">
    <div class="col-xs-3">
		@Html.EditorFor(model => model.EventDate, new
		{
			htmlAttributes = Model.IsEditorReadOnly ?
				(object)new { @class = "form-control input-lg", @type = "date", @readonly = "readonly" } :
				(object)new { @class = "form-control input-lg", @type = "date" }
		})
    </div>
</div>
<div class="row">
    <div class="col-xs-3">
		@Html.ReadOnlyEditorFor(model => model.EventDate, new { @class = "form-control input-lg", @type = "date" }, Model.IsEditorReadOnly)
    </div>
</div>

The solution is to not call it twice in the razor since it will only work correctly the first time. ¯_(ツ)_/¯