HtmlHelper Extension MVC4 RSS

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  tfierens

  Member

  6 Points

  30 Posts

  HtmlHelper Extension MVC4

  Jan 17, 2013 01:53 AM|LINK

  Hi,

  I'm trying to create an htmlhelper extension in MVC4, but I'm having problem when trying to call it. Every samples I've found on the web are similar to what I'm using but somehow, while they all have the "this HtmlHelper html" parameter, none require to call it in the .cshtml page but for some reason, it's expecting in mine!!

  Here is my Extension class:

  public static class HtmlHelperExtensions
      {
          public static string Image(this HtmlHelper helper, string name, string url)
          {
              return Image(helper, name, url, null);
          }
  
          public static string Image(this HtmlHelper helper, string name, string url, object htmlAttributes)
          {
              var tagBuilder = new TagBuilder("img");
  
              tagBuilder.GenerateId(name);
              tagBuilder.Attributes["src"] = new UrlHelper(helper.ViewContext.RequestContext).Content(url);
              tagBuilder.MergeAttributes(new RouteValueDictionary(htmlAttributes));
  
              return tagBuilder.ToString();
          }
      }

  and here is the my code in my .cshtml file:

      @if (Model != null)
      {
          foreach (var item in Model)
          {
          <tr>
              <td>
                  @item.Size
              </td>
              <td>
                  (@item.Size / 1000) KB
              </td>
              <td>
                  @WebTestUpload.HtmlHelperExtensions.Image("previewImage", item.Name, item.Path, new { width = 100, height = 100 }) 
                  @*<img src='Url.Content(@item.Path)' alt='item.Name' />*@
              </td>
          </tr>
          }
      }

   

  But it's giving the following error when I run my app:

  The best overloaded method match for 'WebTestUpload.HtmlHelperExtensions.Image(System.Web.Mvc.HtmlHelper, string, string, object)' has some invalid arguments

  Any ideas?

  Thanks.
   

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  CPrakash82

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  18290 Points

  2844 Posts

  Re: HtmlHelper Extension MVC4

  Jan 17, 2013 03:03 AM|LINK

  tfierens

  this HtmlHelper helper

  This suggest that you are defining an extension for the specified class (HtmlHelper in this case), and you can call that method like a static method of that class.

  tfierens

  @WebTestUpload.HtmlHelperExtensions.Image("previewImage", item.Name, item.Path, new { width = 100, height = 100 })

  You need to change the call like this.

  @Html.Image("previewImage", item.Name, item.Path, new { width = 100, height = 100 })

   

  http://cprakash.com
  • Marked as answer by tfierens on Jan 17, 2013 05:32 PM
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  tfierens

  Member

  6 Points

  30 Posts

  Re: HtmlHelper Extension MVC4

  Jan 17, 2013 01:29 PM|LINK

  I tried what you suggested, but no luck. I get this error now:

  Compiler Error Message: CS1061: 'System.Web.Mvc.HtmlHelper<dynamic>' does not contain a definition for 'Image' and no extension method 'Image' accepting a first argument of type 'System.Web.Mvc.HtmlHelper<dynamic>' could be found (are you missing a using directive or an assembly reference?)

  Any other suggestions?

• • Reply
  

  CPrakash82

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  18290 Points

  2844 Posts

  Re: HtmlHelper Extension MVC4

  Jan 17, 2013 01:37 PM|LINK

  You need to use the namespace before you call this method. i.e using statement in the start of the file

  @using WebTestUpload

   

  http://cprakash.com
  • Marked as answer by tfierens on Jan 17, 2013 05:32 PM
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  tfierens

  Member

  6 Points

  30 Posts

  Re: HtmlHelper Extension MVC4

  Jan 17, 2013 05:32 PM|LINK

  Bang on!! Thank you for that! Messy from MS if you ask me, well at the very least not obvious!

  One small thing I'll add here in case some one else reads this thread, but performing the above will solve your problem but you may end up with the following exception being thrown:

  CS1973: 'System.Web.Mvc.HtmlHelper<dynamic>' has no applicable method named 'Image' but appears to have an extension method by that name. Extension methods cannot be dynamically dispatched. Consider casting the dynamic arguments or calling the extension method without the extension method syntax.

  This is caused (again, strange behaviour or outcome I think!) because one of my model's properties needs to be cast as a string

  @Html.Image("previewImage", (string)item.Path, new { width = 100, height = 100 })

  Thanks again!