Why Enum's HasFlag method need boxing?

Question

I am reading \"C# via CLR\" and on page 380, there\'s a note saying the following:

Note The Enum class defines a HasFlag method defined as follows

Answer 1

Moreover, there's more than single boxing in Enum.HasFlag:

public bool HasFlag(Enum flag)
{
    if (!base.GetType().IsEquivalentTo(flag.GetType()))
    {
        throw new ArgumentException(Environment.GetResourceString("Argument_EnumTypeDoesNotMatch", new object[]
        {
            flag.GetType(),
            base.GetType()
        }));
    }
    ulong num = Enum.ToUInt64(flag.GetValue());
    ulong num2 = Enum.ToUInt64(this.GetValue());
    return (num2 & num) == num;
}

Look at GetValue method calls.

Update. Looks like MS had optimized this method in .NET 4.5 (the source code has been downloaded from referencesource):

    [System.Security.SecuritySafeCritical]
    public Boolean HasFlag(Enum flag) { 
        if (flag == null)
            throw new ArgumentNullException("flag"); 
        Contract.EndContractBlock(); 

        if (!this.GetType().IsEquivalentTo(flag.GetType())) { 
            throw new ArgumentException(Environment.GetResourceString("Argument_EnumTypeDoesNotMatch", flag.GetType(), this.GetType()));
        }

        return InternalHasFlag(flag); 
    }

    [System.Security.SecurityCritical]  // auto-generated 
    [ResourceExposure(ResourceScope.None)]
    [MethodImplAttribute(MethodImplOptions.InternalCall)] 
    private extern bool InternalHasFlag(Enum flags);