@model string
@{
    Layout = "_FieldLayout.cshtml";

    var htmlAttributes = new RouteValueDictionary();
    if (ViewBag.@class != null)
    {
        htmlAttributes.Add("class", ViewBag.@class);
    }

    var isChecked = !string.IsNullOrEmpty(Model);
    var id = ViewData.TemplateInfo.GetFullHtmlFieldId("");
}

<input id="@id" name="@id" type="checkbox" 
       @if(isChecked) {<text>checked="checked"</text>} 
       @if(htmlAttributes.ContainsKey("class")){<text>class="@htmlAttributes["class"]"</text> } />