c# - Avoiding string allocations on native-to-managed callbacks -

i have native library passes hardware data managed code via callbacks.
basic native-to-managed plumbing done by

[dllimport("library.dll")] public static extern bool init(intptr datacallback)  [unmanagedfunctionpointer(callingconvention.stdcall)] public delegate void data(string data);  ...  var handler = marshal.getfunctionpointerfordelegate(handledata); init(handler);  ...  private static void handledata(string data) {     //use data } 

the above works fine.
however, because handledata can called hundreds or thousands of times second (depending on exact hardware module) , data string can quite long, creates noticeable pressure on gc.

avoid creation of strings , instead receive data char[] or byte[] need extract few fields.
tried substitute 'string' stringbuilder or char[] didn't work.

additional information:
- native library passes data char * (null terminated string)
- memory allocated , released native code
- .net version: 4.5

i appreciate help.
thank you!

have tried changing callback signature this?

[unmanagedfunctionpointer(callingconvention.stdcall)] public delegate void data(intptr data);   private unsafe static void handledata(intptr data)     {         byte* charptr = (byte*)data;          // work bytes here (which single-byte chars).       } 

here need cautios , check null character manually.