how to reduce time to export excel in c#

Question

hello all ,

i need to reduce execution time to export excel in c#. i have dataset and i am writing in excel file using closedxml 
.it taking 45 seconds.. i measured time using stop watch..how can i reduce time to 3 to 5 seconds from 45 seconds.

 i am  attaching code snap please review my code where i can optimise my code to reduce execution time.

this is my code where i am adding dataset ... it is taking time ....please help where i can optimise .
thanx in advanced.