Read custom attribute

private static string GetBuildHashFromAssembly()
{
    var assembly = Assembly.GetExecutingAssembly();
    var customAttributes = assembly?.CustomAttributes ?? Enumerable.Empty<CustomAttributeData>();
    return customAttributes
        // MSBuildGitHash adds custom attribute to assembly of the following format:
        // [assembly: AssemblyMetadata("GitHash", "MYHASHVAL")]
        .Where(c => c.ConstructorArguments.Count >= 2 && c.ConstructorArguments[0].Value as string == "GitHash")
        .Select(c => c.ConstructorArguments[1].Value as string)
        .FirstOrDefault() ?? "??";
}