540545 Split large log files in c sharp

Hi, i have to build a simple tool in csharp which searches large log files (2 gb and more may be 10)which has timestamps every one second and cut a certain part (between start timestamp and end timestamp given by the user)..The part should be cut and saved in another text file.i need an efficient way to do this and note that fstream class can deal with files less than 2 gb in size. best regards.