The SetLastWriteTime and GetLastWriteTime methods are used 
to set and get the last write date and time of the specified file. The following 
code snippet sets and gets the last write date and time of a file.
// Get and set file last write time
string fileName = 
@"c:\temp\Mahesh.txt";
File.SetLastWriteTime(fileName,
DateTime.Now);
DateTime dt = 
File.GetLastWriteTime(fileName);
Console.WriteLine("File 
last write time: {0}", dt.ToString());