New .NET 4.0 Feature: Enum.HasFlag()
A minor inclusion to the new .NET 4.0 framework is the addition of the Enum.HasFlag() method. It behaves much like you’d expect, allowing you to check whether an enum instance contains a given flag.
[Flags]
public enum PacketOptions
{
None = 0x00,
All = 0xff,
Compressed = 0x01,
Encrypted = 0x02,
}
PacketOptions opts = PacketOptions.All;
Assert.That(opts.HasFlag(PacketOptions.Compressed), Is.True);
Previously, flag testing was done using (opts & PacketOptions.Compressed) != 0, which was a little awkward because the != operator has higher precedence than &, hence the extraneous parenthesis.
If you’d attempted to implement your own HasFlag extension method, you’d have realized that it was not possible due to the way C# handles its type constraints (yep, I’ve been there).
Discovered via Reed Copsey.