asp.net mvc 3 - Set the values of hidden fields though C# Code? -

i trying set values of 2 hidden fields c# code. these feilds hold error message , exception.

the process run download valuation file , run other code.

this process returns percentage of process , done threads.

as done threads when error can't redirect action error page. add error message hidden field's , display them on error page.

i have tried using tempdate[] , session[] keep returning null once navigate error page.

so if set error message hidden fields pull them of hidden fields once navigated error page great.

could please tell me how this?