Using string.IsNullOrEmpty on a potential string in Razor in Umbraco

Question

I am using a simple method to output a image, and if the media type has a link attached to it, it will act as a link. This method has been working for months and months, but suddenly a customer complained over it not working.

My razor macro in its entirety looks like this:

@using umbraco.MacroEngines
@inherits umbraco.MacroEngines.DynamicNodeContext

@{
    var topImageId = Model._topImage;

    if ( topImageId != null ) {

        var topImage = Library.MediaById(topImageId);
        var linkId = topImage._link;
        string cssStyle = string.Format( "background-image:url({0});height:{1}px;", topImage.umbracoFile, topImage.umbracoHeight );

        <div id="topImage"

        @if(!string.IsNullOrEmpty(linkId)){

            var tempNode = @Model.NodeById(linkId);
            @Html.Raw(string.Format(" onclick=\"window.location.href='{0}'\"", @tempNode.Url));

            cssStyle += " cursor: pointer;";
        }

        @Html.Raw( string.Format( "style=\"{0}\"", cssStyle ) )

        ></div>

    }
}

and it produces these two errors:

Error Loading Razor Script (file: Top Image) The best overloaded method match for 'string.IsNullOrEmpty(string)' has some invalid arguments    at CallSite.Target(Closure , CallSite , Type , Object )
  at System.Dynamic.UpdateDelegates.UpdateAndExecute2[T0,T1,TRet](CallSite site, T0 arg0, T1 arg1)
  at ASP._Page_macroScripts_general_topImage_cshtml.Execute() in d:\inetpub\wwwroot\friendtex.com\www\macroScripts\general\topImage.cshtml:line 15
  at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
  at System.Web.WebPages.WebPage.ExecutePageHierarchy(IEnumerable`1 executors)
  at System.Web.WebPages.WebPage.ExecutePageHierarchy()
  at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
  at umbraco.MacroEngines.RazorMacroEngine.ExecuteRazor(MacroModel macro, INode currentPage)
  at umbraco.MacroEngines.RazorMacroEngine.Execute(MacroModel macro, INode currentPage) 0.741249    0.004230

and

Error loading MacroEngine script (file: /general/topImage.cshtml, Type: ''
The best overloaded method match for 'string.IsNullOrEmpty(string)' has some invalid arguments
  at umbraco.macro.renderMacro(Hashtable pageElements, Int32 pageId)

I suspected the image itself to be the root of the cause, but the media image is absolutely as it should be and I cant see any difference. And to add to the weird-factor - the macro works just perfect with any other image. The image that fails can be found here

EDIT:

For some odd reason, if I do GetType() on the image as Douglas suggested, and it returns a Umbraco.MacroEngines.DynamicXml object, where it on any other image returns a string. It just keep on getting weirder and weirder.

SECOND EDIT:

I decided to throw the code out and rewrite the entire thing using the technique Kevin Hendricks suggested. Now all of a sudden, I get no errors and it works just perfectly. Only difference is a couple of .ToString() a couple of places.

Answer 1

It sounds stupid but you might want to convert the var linkId to a string. If for some reason the generic var object sees it as an integer, Uri or different, than problems like these will arrise

var topImage = Library.MediaById(topImageId);
var linkId = topImage._link;
if (!string.IsNullOrEmpty(linkId.ToString()))
{

}

Prefer:

var topImage = Library.MediaById(topImageId); 
string linkId = topImage._link.ToString(); 
if (!string.IsNullOrEmpty(linkId)) 
{ 

}