I needed to get the Build date of an assembly to write a Really Insecure™ time-limited demo for a client. Simply put, the software should only run within 45 days of being built.

Suggestions from other developers included using Visual Studio’s automated build numbering, and converting the build numbers to a date. Jeff Atwood blogged about a better solution he got from another (now 404ed) source.

He reads the Portable Executable file header, reads out the linker timestamp, and converts it to local time. Easy! Below is the code in C#. See here for a VB.NET version.

private static DateTime RetrieveLinkerTimestamp(string filePath)
{
const int PeHeaderOffset = 60;
const int LinkerTimestampOffset = 8;
byte[] b = new byte[2048];
Stream s = new FileStream(filePath, FileMode.Open, FileAccess.Read);
s.Read(b, 0, 2048);
s.Close();
int i = BitConverter.ToInt32(b, PeHeaderOffset);
int SecondsSince1970 = BitConverter.ToInt32(b, (i + LinkerTimestampOffset));
DateTime dt = new DateTime(1970, 1, 1, 0, 0, 0);
dt = dt.AddSeconds(SecondsSince1970);
dt = dt + TimeZone.CurrentTimeZone.GetUtcOffset(dt);
return dt;
}

Other authors have used the interpreted version number technique, including Kevin Gearing and this article on CodeProject. Still others have simply used the file modification date. Another possibility is embedding the build date in the description of your assembly. This strategy seemed a little more reliable than the others. After all, this is serious business.

Tags: .net, c#