MVC Html Extension return string instead of html m

问题:

If I have en extension like that :

 public static string ImageLink(this HtmlHelper htmlHelper,
                                      string imgSrc, 
                                      string alt, 
                                      string actionName,
                                      string controllerName, 
                                      object routeValues, 
                                      object htmlAttributes, 
                                      object imgHtmlAttributes)
  {

     return @"<img src=""../../Content/images/english.png"" /> ";
  }

and I use it in a partial view like this :

@Html.ImageLink("../../Content/images/english.png","English", "ChangeCulture", "Account", new { lang = "en", returnUrl = this.Request.RawUrl }, null,null)

I have an output like this :

Any idea why?

回答1:

The reason this happens is because the @ operator in Razor automatically HTML encodes. If you want to avoid this encoding you need to use an IHtmlString:

public static IHtmlString ImageLink(
    this HtmlHelper htmlHelper,
    string imgSrc, 
    string alt, 
    string actionName,
    string controllerName, 
    object routeValues, 
    object htmlAttributes, 
    object imgHtmlAttributes
)
{
    return MvcHtmlString.Create(@"<img src=""../../Content/images/english.png"" />");
}

which obviously will be far more correct (and working in all situations, no matter from where and how this helper is called) if written like this:

public static IHtmlString ImageLink(
    this HtmlHelper htmlHelper,
    string imgSrc,
    string alt,
    string actionName,
    string controllerName,
    object routeValues,
    object htmlAttributes,
    object imgHtmlAttributes
)
{
    var img = new TagBuilder("img");
    var urlHelper = new UrlHelper(htmlHelper.ViewContext.RequestContext);
    img.Attributes["src"] = urlHelper.Content("~/Content/images/english.png");
    // Don't forget that the alt attribute is required if you want to have valid HTML
    img.Attributes["alt"] = "English flag"; 
    return MvcHtmlString.Create(img.ToString(TagRenderMode.SelfClosing));
}

and then

@Html.ImageLink("../../Content/images/english.png","English", "ChangeCulture", "Account", new { lang = "en", returnUrl = this.Request.RawUrl }, null,null)

will work properly.

As an alternative if you cannot modify the helper you could use @Html.Raw:

@Html.Raw(Html.ImageLink("../../Content/images/english.png","English", "ChangeCulture", "Account", new { lang = "en", returnUrl = this.Request.RawUrl }, null,null))

回答2:

Have it return MvcHtmlString instead (my sample below).

 public static MvcHtmlString IconImg(this HtmlHelper htmlHelper, string icon, string title = "", string size = "16x16") {
        string path = VirtualPathUtility.ToAbsolute("~/res/img/icons/" + size + "/" + icon + ".png");
        string imgHtml = "<img src='" + path + "' title='" + title + "' style='border:none' />";
        return new MvcHtmlString(imgHtml);
    }