How to marshal DWORD in C#?

[Geming Leader]

I have a quesion about DWORD.

When I have looked on DWORD on MSDN:
http://msdn.microsoft.com/en-us/libr...51(VS.85).aspx

I found that it is "unsigned 32-bit integer," so I marshaled it as System.UInt32. In addition, I found it marshaled as System.UInt32 in many places.

But, when I tried to PInvoke GetStdHandle() function:
http://msdn.microsoft.com/en-us/libr...51(VS.85).aspx

I found that it takes one of three values:
A. -10: to retrieve input device handle
B. -11: to retrieve output device handle
C. -12: to retrieve error device handle

Although, DWORD is "unsigned 32-bit integer" and it is marshaled System.UInt32, System.UInt32 does not support negative values, therefore, it cannot take any value of the three. So, I have marshaled it as System.Int32 instead.

Now, the question is:
Do I have a misconception about DWORD? And why we marshal DWORD to System.UInt32 and GetStdHandle() requires negative values?

[darwen]

To be CLS compliant you can't use unsigned types (except for byte).

The correct CLS compliant way of marshalling DWORD is to int.

When marshaling, the size of the type is important : not what the resultant outcome is with integer types. Because int & uint are both the same size (4 byes) you don't have a problem.

With regards to negative values, look up how negative values are held in memory on google (e.g. here).

-1 = 0xFFFFFFFF for instance.

Marshaling to int is ok for DWORD unless dealing with values > 0x80000000. The top bit represents of the 32-bits in a DWORD signifies a negative value.

If the value is > 0x80000000 and you need it not to be negative covert it to a long which is 64-bits by doing the following :

static long IntToLong(int value)
{
    return ((long)value) & 0xFFFFFFFFL;
}

Darwen.

[Geming Leader]

I am very thankful Darwen. The code segment was very brilliant.

But I know that the size reserved for the variable is more important, and System.UInt32 is non-CLS-compliant. But the question here, why GetStdHandle() requires DWORD? I think it would be OK if it requires INT instead!