Converting Between MFC/C++ and .NET Types

Monday Jul 19th 2004 by Tom Archer
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Converting between types is frequently a sticking point for coders new to mixing MFC and .NET. Tom Archer illustrates some basic conversions that will help you should you get stuck in a painful series of compiler error messages about type mismatches.

Welcome to this week's installment of .NET Tips & Techniques! Each week, award-winning Architect and Lead Programmer Tom Archer from the Archer Consulting Group demonstrates how to perform a practical .NET programming task using either C# or Managed C++ Extensions.

Many .NET methods are very picky about the types that you can pass as parameters. For example, the sockets, cryptography, and several of the streaming methods require byte arrays, which you must first convert from CString objects or C++ types. In addition, despite the fact that IJW alleviates many conversion issues, several situations still require you to manually convert a .NET type to a C++ type. As a result, converting between types is frequently a sticking point for coders new to mixing MFC and .NET. This article illustrates some basic conversion code that should help you if you find yourself about to throw your monitor against the wall after the latest "can't convert x to y" compiler error message!

Converting CString objects to .NET Byte array

CString str = _T("CString to be converted to a byte array");
Byte barr[] = new Byte[str.GetLength()];
for(int i = 0; i < str.GetLength(); i++)
 barr[i] = static_cast<Byte>(str [i]);

Converting String objects to C++ char array

#include <vcclr.h> // Needed for the PtrToStringChars function
//...
String* s = S"String to be converted to a char array";
const __wchar_t __pin * str = PtrToStringChars(s);

Converting String objects to .NET Byte array

String* str = S"String to be converted to a byte array";	
Byte barr[] = new Byte[str->Length];
for(int i=0; i<str->Length; i++)
  barr[i] = static_cast<Byte>(str->ToCharArray()[i]);

Converting Int32 objects to managed char array

Int32 myInt = 42;
unsigned char myArray __gc[] = BitConverter::GetBytes(myInt);

Got More?

This is by no means meant to be a complete composition of all conversions between MFC/C++ and .NET. However, it will handle the majority of the cases you face. If you would like to add a conversion, just drop me a line. If I add it to the article, I'll, of course, give you credit for the input.

About the Author

The founder of the Archer Consulting Group (ACG), Tom Archer has been the project lead on three award-winning applications and is a best-selling author of 10 programming books as well as countless magazine and online articles.

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