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Converting C++ Data Types to C#

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
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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
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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
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carlo giordano
1 discussion post
hi , c++ type ctime how can be converted in c# ?
Aug 31, 2010  • #4
Jon Tackabury (BFS)'s profile on
@Carlo: It looks like ctime is just an int64:
Aug 31, 2010  • #5
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1 discussion post
CTime, CTimeSpan convert C#?
Aug 6, 2012  • #6
Jon Tackabury (BFS)'s profile on
@cesc: Sorry, I'm not familiar with those types, and I've never had to convert them. :(
Aug 7, 2012  • #7
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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
Jon Tackabury (BFS)'s profile on
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
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Joe Rodriguez
1 discussion post
unsigned char c++ convert to c#?
Dec 18, 2013  • #10
Jon Tackabury (BFS)'s profile on
"unsigned char" is a byte in C#. A C# byte is an unsigned 8bit type, just the unsigned char.
Dec 18, 2013  • #11
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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
Jon Tackabury (BFS)'s profile on
@Jody: Thanks, I must have missed that one. It's on the list now. :)
May 29, 2015  • #13
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1 discussion post
How do we get those nasty Timestamps from ULONGLONG?
Jul 13, 2015  • #14
Jon Tackabury (BFS)'s profile on
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:
Jul 13, 2015  • #15
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1 discussion post
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
Jon Tackabury (BFS)'s profile on
@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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