pinvoke - How to marshal an array of structure In C#? -

i have call c++ dll in c#. , header of dll following(simplified):

//header of c++

struct vector {     float x;     float y;      vector()     {}      vector(float x0, float y0)     {         x = x0;         y = y0;     } };  struct unmanaged_struct {     int int_var;     float float_var;     char* chars_var;     vector vector_var;      unmanaged_struct(int i, float f, char* ch, float vec_x, float vec_y)      {         int_var = i;         float_var = f;         chars_var = ch;         vector_var = vector(vec_x, vec_y);     } }; 

// function used output variable values of struct instance

extern "c" __declspec( dllexport )  void unmanagedstruct_summary(unmanaged_struct* us_list, int length); 

and defined following class in c#

//csharp

[structlayout(layoutkind.sequential)] public class vector {     public float x;     public float y;      public vector(float f1, float f2)     {         x = f1;         y = f2;     } }  [structlayout(layoutkind.sequential)] public class unmanagedstruct  {      public int int_var;     public float float_var;     public string char_var;     public vector vector_var;      public unmanagedstruct(int i, float f, string s, vector vec)     {         this.int_var = i;         this.float_var = f;         this.char_var = s;         this.vector_var = vec;     } }  class unmanageddllcalltest {     [dllimport("unmanageddll.dll", entrypoint = "unmanagedstruct_summary")]     public  static extern void unmanagedstruct_summary([out]unmanagedstruct[] uslist, int length);        static void main(string[] args)     {          unmanagedstruct[] uslist = new unmanagedstruct[1];         uslist[0] = new unmanagedstruct(1, 1.0f, "aa", new vector(10, 1));                uslist[1] = new unmanagedstruct(2, 2.0f, "ba", new vector(20, 2));           unmanageddllcalltest.unmanagedstruct_summary(uslist, 2); } 

and output following:

unmanaged_struct summary:

0

1.12104e-044

unhandled exception: system.accessviolationexception: attempted read or write protected memory. indication other memory corrupt. @ callunmanageddll.unmanageddllcalltest.unmanagedstruct_summary(unmanagedstr uct[] uslist, int32 length) @ callunmanageddll.program.main(string[] args) in c:\users\dynaturtle\docume nts\visual studio 2010\projects\callunmanageddll\callunmanageddll\program.cs:lin e 68

the c++ dll ok have written test in c++ , function works well. have read this thread seems solution didn't work in case. suggestions? in advance!

use marshal.ptrtostructure. there sample here.

so have change signature of method out structure array out intptr. however, need know size of buffer being passed out.

public struct vector {     public float x;     public float y;  }  public struct unmanagedstruct  {      public int int_var;     public float float_var;     public string char_var;     public vector vector_var;  }  class unmanageddllcalltest {     [dllimport("unmanageddll.dll", entrypoint = "unmanagedstruct_summary")]     public static extern void unmanagedstruct_summary([out] intptr ptr, int length);        static void main(string[] args)   {      for(int i=0; i<length; i++)     {         unmanagedstruc st;         marshal.ptrtostructure(ptr, st);         // increment ptr , move forward     }  }