asp.net mvc - TempData is empty when set in a catch block and we rethrow -

i using custom errors (web.config) send unhandled exceptions errorcontroller.

in main controller throw exception, catch in catch block , set tempdata have user-friendly message. throw sent errorcontroller.

when check tempdata here, empty (as session be, wouldn't it?).

i sure not meant empty, , right way of sending data between controllers... not working! mistaken in understanding?

homecontroller:

catch (exception ex) {     tempdata["msgforuser"] = "useful message show";     // logging...      throw; } 

errorcontroller:

public actionresult displayerror(int id) {     viewbag.msgforuser = tempdata["msgforuser"];     return view(); } 

web.config:

<system.web>   <customerrors mode="on" defaultredirect="~/errorpage/displayerror">     <error redirect="~/error/displayerror/403" statuscode="403" />     <error redirect="~/error/displayerror/404" statuscode="404" />     <error redirect="~/error/displayerror/500" statuscode="500" />   </customerrors> 

i found session being destroyed upon doing throw in top-level catch block, because request error controller. did find returning redirecttoaction() preserved it.

so, created own exception type:

public class myapplicationexception : exception {     /// <summary>     /// message can shown user i.e. not technical     /// </summary>     public string messageforuser { get; set; }      public myapplicationexception()     {     }      public myapplicationexception(string message, string messageforuser="")         : base(message)     {         messageforuser = messageforuser;     }      public myapplicationexception(string message, exception inner, string messageforuser = "")         : base(message, inner)     {         messageforuser = messageforuser;     } } 

then when encounter problem expecting , end sending user generic error page, use so:

if (mylist.count > 14) {       throw new myapplicationexception("more 14 records received: " + mylist.count.tostring(), "there maximum limit of 14 records can processed @ time. please call discuss requirement process in greater quantities."); } 

and upon catching pick out message user, log error, , return redirecttoaction() go error page without losing tempdata.

catch (myapplicationexception myappex) {     // if there user-friendly message store displayerror show     if (string.isnullorempty(myappex.messageforuser) == false)     {         tempdata["msgforuser"] = myappex.messageforuser;     }      // logging elmah or custom logger     util.logerror(myappex, "myfunc() threw exception", args);      //     // cannot throw here because lose session & tempdata. have manual redirect.     //     return redirecttoaction("displayerror", "errorpage", new { id = 500 }); } 

and in view, , display if exists:

<p>     error occurred. please check & try again later. </p> @if (string.isnullorempty(viewbag.msgforuser) == false) {     <p class="more-info">details: @viewbag.msgforuser</p> }