PhysicalAddress.Parse() won't parse lower cased string, is this a bug?

Question

Note: Using .Net 4.0

Consider the following piece of code.

String ad = "FE23658978541236";
String ad2 = "00FABE002563447E".ToLower();
try
{
    PhysicalAddress.Parse(ad);
}
catch (Exception)
{
    //We dont get here, all went well
}
try
{
    PhysicalAddress.Parse(ad2);
}
catch (Exception)
{
    //we arrive here for what reason?
}
try
{
    //Ok, I do it myself then.
    ulong dad2 = ulong.Parse(ad2, System.Globalization.NumberStyles.HexNumber);
    byte[] bad2 = BitConverter.GetBytes(dad2);
    if (BitConverter.IsLittleEndian)
    {
        bad2 = bad2.Reverse().ToArray<byte>();
    }
    PhysicalAddress pa = new PhysicalAddress(bad2);
}
catch (Exception ex)
{
    //We don't get here as all went well
}

So an exception is thrown in PhysicalAddress.Parse method when trying to parse an address with lower case. When I look at the source code of .Net its totally clear to me why. Its because of the following piece of code.

    if (value >= 0x30 && value <=0x39){ 
        value -= 0x30;
    } 
    else if (value >= 0x41 && value <= 0x46) {
        value -= 0x37;
    }

That is found within the Parse method.

    public static PhysicalAddress Parse(string address) {
    int validCount = 0; 
    bool hasDashes = false; 
    byte[] buffer = null;

    if(address == null)
    {
        return PhysicalAddress.None;
    } 

    //has dashes? 
    if (address.IndexOf('-') >= 0 ){ 
        hasDashes = true;
        buffer = new byte[(address.Length+1)/3];    
    }
    else{

        if(address.Length % 2 > 0){  //should be even 
            throw new FormatException(SR.GetString(SR.net_bad_mac_address));
        } 

        buffer = new byte[address.Length/2];
    } 

    int j = 0;
    for (int i = 0; i < address.Length; i++ ) {

        int value = (int)address[i];

        if (value >= 0x30 && value <=0x39){ 
            value -= 0x30;
        } 
        else if (value >= 0x41 && value <= 0x46) {
            value -= 0x37;
        }
        else if (value == (int)'-'){ 
            if (validCount == 2) {
                validCount = 0; 
                continue; 
            }
            else{ 
                throw new FormatException(SR.GetString(SR.net_bad_mac_address));
            }
        }
        else{ 
            throw new FormatException(SR.GetString(SR.net_bad_mac_address));
        } 

        //we had too many characters after the last dash
        if(hasDashes && validCount >= 2){ 
            throw new FormatException(SR.GetString(SR.net_bad_mac_address));
        }

        if (validCount%2 == 0) { 
            buffer[j] = (byte) (value << 4);
        } 
        else{ 
            buffer[j++] |= (byte) value;
        } 

        validCount++;
    }

    //we too few characters after the last dash
    if(validCount < 2){ 
        throw new FormatException(SR.GetString(SR.net_bad_mac_address)); 
    }

    return new PhysicalAddress(buffer);
}

Can this be considered a bug? Or is it so very wrong to use a lower cased hex values in a string? Or is there some convention I am unaware of. Personally, I consider this programmer unfriendly.

Answer 1

From MSDN:

The address parameter must contain a string that can only consist of numbers and upper-case letters as hexadecimal digits. Some examples of string formats that are acceptable are as follows .... Note that an address that contains f0-e1-d2-c3-b4-a5 will fail to parse and throw an exception.

So you could simply do: PhysicalAddress.Parse(ad.ToUpper());