Version version = Assembly.GetEntryAssembly().GetName().Version;

System.Reflection.Assembly assembly = System.Reflection.Assembly.GetExecutingAssembly();
FileVersionInfo fvi = FileVersionInfo.GetVersionInfo(assembly.Location);
string version = fvi.FileVersion;

string assemblyVersion = Assembly.GetExecutingAssembly().GetName().Version.ToString();
string assemblyVersion = Assembly.LoadFile('your assembly file').GetName().Version.ToString();
string fileVersion = FileVersionInfo.GetVersionInfo(Assembly.GetExecutingAssembly().Location).FileVersion;
string productVersion = FileVersionInfo.GetVersionInfo(Assembly.GetExecutingAssembly().Location).ProductVersion;

versionlabel.Text = "Version " + Application.ProductVersion;

AssemblyName.Version

((AssemblyFileVersionAttribute)Attribute.GetCustomAttribute(
    Assembly.GetExecutingAssembly(),
    typeof(AssemblyFileVersionAttribute), false)
).Version;

new Version(System.Windows.Forms.Application.ProductVersion);