Marshaling unmanaged char** to managed string[]

Question

I have a C++ function in a DLL file (it is compiled with the Multi-Byte Character Set option):

_declspec(dllexport) void TestArray(char** OutBuff,int Count,i         


        

Answer 1

So OutBuff is basically an array of pointers - so you need to create an IntPtr array whose elements are valid pointers - that is IntPtr values that point to valid memory. Like below:

int count = 10;
int maxLen = 25;
IntPtr[] buffer = new IntPtr[count];

for (int i = 0; i < count; i++)
    buffer[i] = Marshal.AllocHGlobal(maxLen);

TestArray(buffer, count, maxLen);

string[] output = new string[count];
for (int i = 0; i < count; i++)
{
    output[i] = Marshal.PtrToStringAnsi(buffer[i]);
    Marshal.FreeHGlobal(buffer[i]);
}