Converting C++ Data Types to C#

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If you've ever had to write any interop code to use an unmanaged library in your C# application, you know how tricky it can be to get the data types correct. I often find myself scouring the internet looking for the correct conversions, so I thought I would document everything I have learned so far. This is by no means a comprehensive list of all C++ data types, just the ones I find myself frequently writing interop code for.

C++ Type	C# Type	Size
BOOL	bool	1 byte
BYTE	byte	1 byte
CHAR	byte	1 byte
DECIMAL	Decimal	16 bytes
DOUBLE	double	8 bytes
DWORD	uint, UInt32	4 bytes
FLOAT	float, single	4 bytes
INT, signed int	int, Int32	4 bytes
INT16, signed short int	short, Int16	2 bytes
INT32, signed int	int, Int32	4 bytes
INT64	long, Int64	8 bytes
LONG	int, Int32	4 bytes
LONG32, signed int	int, Int32	4 bytes
LONG64	long, Int64	8 bytes
LONGLONG	long, Int64	8 bytes
SHORT, signed short int	short, Int16	2 bytes
UCHAR, unsigned char	byte	1 byte
UINT, unsigned int	uint, UInt32	4 bytes
UINT16, WORD	ushort, UInt16	2 bytes
UINT32, unsigned int	uint, UInt32	4 bytes
UINT64	ulong, UInt64	8 bytes
ULONG, unsigned long	uint, UInt32	4 bytes
ULONG32	uint, UInt32	4 bytes
ULONG64	ulong, UInt64	8 bytes
ULONGLONG	ulong, UInt64	8 bytes
WORD	ushort	2 bytes
void*, pointers	IntPtr	x86=4 bytes, x64=8 bytes

If I am missing something, or you would like me to include something else, please let me know in the comments below. Thanks!

Apr 12, 2010 (modified Mar 17, 2016) • #1

billy.oneal

3 discussion posts

Just an FYI: Those are *not* C or C++ datatypes, they are Win32 API datatypes. Standard C++ does not define any of what you have above excepting `void *`.

Have a nice day

May 3, 2010 • #2

Xenovore

1 discussion post

Good list! (Yeah, there are other types but who uses those...)

Maybe add these though...? C++ has had a native boolean type "bool" for a while now, as well as a floating point types "float" and "double". (Never have understood why they typedef'ed those; I guess they wanted ALL their types to be uppercase...)

@Billy: This _is_ C# interop (i.e. Windows!) we're talking about, so naturally you're dealing with Win32 data types, that are typedef'ed in C++ and native in C#. Thanks though for pointing out the obvious! =P

Jun 28, 2010 • #3

carlo giordano

1 discussion post

hi , c++ type ctime how can be converted in c# ?

Aug 31, 2010 • #4

@Carlo: It looks like ctime is just an int64:
http://bytes.com/topic/c-sharp/answers/259755-convert-c-ctime-c-datetime

Aug 31, 2010 • #5

cesc2

1 discussion post

CTime, CTimeSpan convert C#?

Aug 6, 2012 • #6

@cesc: Sorry, I'm not familiar with those types, and I've never had to convert them.

Aug 7, 2012 • #7

Ronald Chua

1 discussion post

What about strings? I'm trying to convert System.String of C# to char* or unsigned char* in C++. But it was indicated that char* is SByte. I've tried char variable[], std::string, unsigned char*, and none of them worked. I tried converting the System.String to SByte using Convert static method, but then another error shows up, saying SByte can't be converted to SByte*.

Hope to get a response.

Dec 9, 2012 • #8

Strings can be very tricky! I would recommend just using IntPtr for the parameter while trying to figure it out. Once you get the IntPtr value use Marshal.PtrToStr functions to read the string value. I find this is more reliable than relying on the p/invoke marshalling in some situations. I hope this helps!

Dec 10, 2012 • #9

Joe Rodriguez

1 discussion post

unsigned char c++ convert to c#?

Dec 18, 2013 • #10

"unsigned char" is a byte in C#. A C# byte is an unsigned 8bit type, just the unsigned char.

Dec 18, 2013 • #11

Jody McAdams

1 discussion post

You're missing WORD. You have DWORD but no WORD. WORD is same as your listing for UINT16 so in C# it would be Uint16 or ushort.

May 28, 2015 • #12

@Jody: Thanks, I must have missed that one. It's on the list now.

May 29, 2015 • #13

Chas3

1 discussion post

How do we get those nasty Timestamps from ULONGLONG?

Jul 13, 2015 • #14

I'm not sure which timestamp type you're working with exactly, but this post has info on converting from a ULONGLONG to a FILETIME struct:
http://stackoverflow.com/questions/4570194/log-with-timestamps-that-have-millisecond-accuracy-resolution-in-windows-c

Jul 13, 2015 • #15

Suresh7

1 discussion post

Hi,
I have c++ code as below
typedef char MyChar;
public struct OutParameter
{
public MyChar Status;
}

The above c++ struct is returned by reference in function parameter.

Could you please provide me equivalent C# struct .

Nov 13, 2015 • #16

@Suresh: You just need to change "public MyChar Status" to "public chat Status" and it should work in C#. You might need to use the "byte" type instead of "char", but you'll have to test that.

Nov 16, 2015 • #17

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