c++ DLL和c#之间传递字符串

c++代码

 1 extern "C" _declspec(dllexport) bool get(char*& strPorts)
 2 {
 3     string str = "Hello";
 4     int length = str.size() + 1;
 5     strPorts = newchar[length];
 7     strcpy_s(strPorts, length, str.c_str());
 8     return true;
 9 }
10 extern "C" _declspec(dllexport) bool set(char* str)
11 {
12     cout << str << endl;
13     return true;
14 }

c#代码

 1     [DllImport("My.dll")]
 2     public static extern bool get(out IntPtr pstrPorts);
 3     [DllImport("My.dll")]
 4     public static extern bool set(string strPorts);
 5     //调用
 6     IntPtr pStr;
 7     get(out pStr);
 8     System.Console.WriteLine(Marshal.PtrToStringAnsi(pStr));
 9 
10     string str="Hello";
11     set(str);

因为set里面传递的指针是空的，需要dll来new，百度了好久才找到解决方案。