将char *缓冲区作为StringBuilder传递给C＃

Question

I have a C++ function that is called with a char* buffer to be used for the output. Now i want to write to it using C# so i need to call a managed method from the C++ function. What i can't figure out is how to pass it as a StringBuilder.

I previously used Robert Giesecke's Unmanaged Exports which worked fine and did this automatically using a default string marshalling scheme, but i want to use the size parameter for the MaxCapacity of the StringBuilder.

Is there a nicer way to do this than creating a new StringBuilder instance, writing to it, getting a CLR string with ToString() , and then copying the contents to the buffer? The strings in question might be as long as 10,000 characters and i don't really like the idea of copying it twice each time.

C#

public static void MyMethod(StringBuilder buffer)
{
    //...
}

C++/CLI

extern "C" __declspec(dllexport)
void __stdcall MyFunction(char* buffer, int length)
{
    MyNamespace::MyClass::MyMethod( /* ? */ );
}

Answer 1

1. Use a byte [] then c++ 8 bit character array will align correctly.

2. I prefer to do something similar to this because I use it for unmanaged code:

    String ^ ToManagedString(const char * pString) { return Marshal::PtrToStringAnsi(IntPtr((char *)pString)); // Marshal pString into Managed Memory. return as a C# string reference (^). } const std::string ToStdString(String ^ strString) { IntPtr ptrString = IntPtr::Zero; std::string strStdString; try { ptrString = Marshal::StringToHGlobalAnsi(strString); // Marshal a C# String reference into unmanaged HEAP memory space. strStdString = (char *)ptrString.ToPointer(); // Convert C# IntPtr to char* implicitly, call assignment operator of std::string to copy. } finally { if (ptrString != IntPtr::Zero) { Marshal::FreeHGlobal(ptrString); } } return strStdString; // return std::string copied out of interop unmanaged heap space }