asp.net mvc - Unable to reference the InnerException.Message inside Catch(Exception ex) -

i have following code part of action method inside asp.net mvc web application:-

catch (exception ex) {       using (var client = new webclient())       {            var query = httputility.parsequerystring(string.empty);           xmldocument do2c = new xmldocument();           query["username"] = system.web.configuration.webconfigurationmanager.appsettings["apiusername"];           query["password"] = system.web.configuration.webconfigurationmanager.appsettings["apipassword"];           query["assettype"] = routedata.values["controller"].tostring();           query["operation"] = "deleteasset";           query["assetname"] = vmj.resource.resourcename;           query["accountname"] = vmj.customer.name;           query["sitename"] = sitename;           string apiurl = system.web.configuration.webconfigurationmanager.appsettings["apiurl"];           var url = new uribuilder(apiurl);           url.query = query.tostring();           try           {               string xml = client.downloadstring(url.tostring());               xmldocument doc2 = new xmldocument();               doc.loadxml(xml);             }           catch (webexception ex2)           {               modelstate.addmodelerror(string.empty, "error occurred:" + ex2.innerexception.message);           }           //}           //}       }       modelstate.addmodelerror(string.empty, "error occurred:" + ex.innerexception.message);   } } 

but when exception ex occur, unable display innerexception.message, , null reference exception when trying reference innerexception.message. although have added brake point , ex object contains both inner-exception , message describing exception. idea going on ?