I have changed DPF sensor on C250 CDI 2011 now its miss-firing im told by mercedes that its injector number 1 and 4.

 

Diesels don't misfire. What are you talking about and why did Mercedes tell you there is an issue with the injectors.

 

Diesels “misfire” if the injector fails to deliver the proper amount of fuel. The Ford Powerstroke 6.0L was well known for this.

Do you have the OM651 engine? Seems there is a lot written about injector replacement on this engine. Google can find it for you.