托管代码数据怎么转非托管数据？array<Byte> 怎样转为 char *

#include<windows.h>using namespace System;using namespace System::Runtime::InteropServices;#pragma comment( lib , "User32.lib" )int main(array<System::String ^> ^args){    array <Byte>^ arr = gcnew array<Byte>(128);    for(int i=0;i<26;i++)        arr[i]='a'+i;    IntPtr p = Marshal::UnsafeAddrOfPinnedArrayElement( arr , 0 );    ::MessageBoxA( 0 , (char*)p.ToPointer() , 0 , 0 );    return 0;}