Question

I currently have an app displaying the build number in its title window. That’s well and good except it means nothing to most of the users, who want to know if they have the latest build – they tend to refer to it as “last Thursday’s” rather than build 1.0.8.4321.

The plan is to put the build date there instead – So “App built on 21/10/2009” for example.

I’m struggling to find a programmatic way to pull the build date out as a text string for use like this.

For the build number, I used:

Assembly.GetExecutingAssembly().GetName().Version.ToString()

after defining how those came up.

I’d like something like that for the compile date (and time, for bonus points).

Pointers here much appreciated (excuse pun if appropriate), or neater solutions…

Answer 1

Jeff Atwood had a few things to say about this issue in Determining Build Date the hard way.

The most reliable method turns out to be retrieving the linker timestamp from the PE header embedded in the executable file — some C# code (by Joe Spivey) for that from the comments to Jeff’s article:

public static DateTime GetLinkerTime(this Assembly assembly, TimeZoneInfo target = null)
{
    var filePath = assembly.Location;
    const int c_PeHeaderOffset = 60;
    const int c_LinkerTimestampOffset = 8;

    var buffer = new byte[2048];

    using (var stream = new FileStream(filePath, FileMode.Open, FileAccess.Read))
        stream.Read(buffer, 0, 2048);

    var offset = BitConverter.ToInt32(buffer, c_PeHeaderOffset);
    var secondsSince1970 = BitConverter.ToInt32(buffer, offset + c_LinkerTimestampOffset);
    var epoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);

    var linkTimeUtc = epoch.AddSeconds(secondsSince1970);

    var tz = target ?? TimeZoneInfo.Local;
    var localTime = TimeZoneInfo.ConvertTimeFromUtc(linkTimeUtc, tz);

    return localTime;
}

Usage example:

var linkTimeLocal = Assembly.GetExecutingAssembly().GetLinkerTime();

---

Note: this method works for .NET Core 1.0, but stopped working after .NET Core 1.1 – it gives random years in the 1900-2020 range.