>>>>>>>>(1) The short way is to cast the return result to UInteger, and change the return type of GetCrc32() to UInteger
>>>>>>>
>>>>>>>IIRC you can't do that cast in VB (although you can in C# using 'unchecked')
>>>>>>
>>>>>>
>>>>>>Viv,
>>>>>>
>>>>>>I don't know, but I'd be very surprised if it weren't possible
>>>>>
>>>>>Just tried this which won't compile:

Dim test As UInteger = DirectCast(Int32.MaxValue, UInteger)

>>>>>If it was a valid cast what resulting UInteger would you expect from a negative value signed int ?
>>>>>In C#:

unchecked { UInt32 test = ((UInt32)Int32.MinValue); }

>yields 2147483648....
>>>>
>>>>
>>>>Firstly, I'm surprised that it yields an even number
>>>>
>>>>Secondly, if that's the case, I guess you'll need t check whether is was negative, and if so, set the left most bit after the 'cast'
>>>
>>>But if the signed int is negative then there is no accurate equivalent for an unsigned int ?
>>>I'm assuming the C# cast simple treats the 32 bits as being an unsigned value ?
>>>FWIW:

unchecked { Int32 test = ((Int32)UInt32.MaxValue);

>gives -1
>>
>>
>>Yes, of course, all bits set is signed -1 and unsigned the max value
>>
>>When the leftmost bit is set in a signed int type, then it is considered as negative
>>
>>>But if the signed int is negative then there is no accurate equivalent for an unsigned int ?
>>
>>Viv, this isn't about maths. The crc32 is just a structure that is 32 bits wide
>
>That's why I said : "I'm assuming the C# cast simple treats the 32 bits as being an unsigned value"
>
>>If you think about it as a signed 32 bit structure and the leftmost bit is set then the number is negative
>>
>>If you look at it as an unsigned 32 bit structure, the same pattern is a number >= 0
>
>I understand that - my point was that, in normal application usage, converting a negative signed int to an unsigned int would not make sense.


Well, if the cast does not work, I think I have figured out how to - pardon the syntax - and untested

If the number is not negative, I see no problem in converting

If it is, then
set the sign bit to 0
convert to UInteger
add 0x80000000UI
endif

Private Function GetCrc32(ByRef toStream As System.IO.Stream) As UInteger

   '  the code
   ' Return Not lnCRC32Result
   dim result as UInteger
   if( lnCRC32Result >= 0 )  then
       result = CUInt( lnCRC32Result)
  else
       result = CUInt(lnCRC32Result and &7FFFFFFF) + &80000000UI
  endif
   return not result