Blog Code: MVC Razor Helpers Using Delegates

HtmlHelperExtensions_methods.cs

public static HelperResult RenderIf<TType>(this HtmlHelper html, Func<TType, HelperResult> template, TType item, bool condition)
{
    return html.RenderIf(template, new TType[] { item }, condition);
}
 
public static HelperResult RenderIf<TType>(this HtmlHelper html, Func<TType, HelperResult> template, IEnumerable<TType> items, bool condition)
{
    if (condition)
    {
        return new HelperResult(writer =>
        {
            foreach (var item in items)
            {
                template(item).WriteTo(writer);
            }
        });
    }
 
    //return a blank template
    return new HelperResult(writer => { });
}

HtmlHelperExtensions_shell.cs

public static class HtmlHelperExtensions
{
}

HtmlHelperExtensions_sugar.cs

public static HelperResult RenderIfInRole<TType>(this HtmlHelper html, Func<TType, HelperResult> template, TType item, string role)
{
    return html.RenderIf(
            template, 
            item, 
            html.ViewContext.HttpContext.User.IsInRole(role)
        );
}

view.cshtml

@Html.RenderIf(@<text>
        <strong>@item.Propertu</strong><br />
    </text>,
    items,
    items.Count > 0
)
 
@Html.RenderIf(@<text>
    <p><a href="@Url.Action("logout")">Logout @item.Name</a></p>
    </text>,
    this.User.Identity,
    this.Request.IsAuthenticated
)