Marshaling Different Types of Arrays

// Declares a managed structure for each unmanaged structure.
[ StructLayout( LayoutKind.Sequential )]
public struct MyPoint 
{
   public int x; 
   public int y;
   public MyPoint( int x, int y )
   {
      this.x = x;
      this.y = y;
   }
}
[ StructLayout( LayoutKind.Sequential, CharSet=CharSet.Ansi )]
public struct MyPerson 
{
   public String first; 
   public String last;
   public MyPerson( String first, String last )
   {
      this.first = first;
      this.last = last;
   }
}

public class LibWrap
{
   // Declares a managed prototype for an array of integers by value. 
   // The array size cannot be changed, but the array is copied back.
   [ DllImport( "..\\LIB\\PinvokeLib.dll" )]
   public static extern int TestArrayOfInts([In, Out] int[] array, int size );

   // Declares a managed prototype for an array of integers by reference. 
   // The array size can change, but the array is not copied back  
   // automatically because the marshaler does not know the resulting size. 
   // The copy must be performed manually.
   [ DllImport( "..\\LIB\\PinvokeLib.dll" )]
   public static extern int TestRefArrayOfInts( ref IntPtr array, 
      ref int size );

   // Declares a managed prototype for a matrix of integers by value.
   [ DllImport( "..\\LIB\\PinvokeLib.dll" )]
   public static extern int TestMatrixOfInts([In, Out] int[,] pMatrix, 
      int row );   
   // Declares a managed prototype for an array of strings by value.
   [ DllImport( "..\\LIB\\PinvokeLib.dll" )]
   public static extern int TestArrayOfStrings( [In, Out] 
      String[] stringArray, int size );

   // Declares a managed prototype for an array of structures with integers.
   [ DllImport( "..\\LIB\\PinvokeLib.dll" )]
   public static extern int TestArrayOfStructs([In, Out] MyPoint[] 
      pointArray, int size ); 

   // Declares a managed prototype for an array of structures with strings.
   [ DllImport( "..\\LIB\\PinvokeLib.dll" )]
   public static extern int TestArrayOfStructs2( [In, Out] 
      MyPerson[] personArray, int size );
}

public class App
{
   public static void Main()
   {
      // array ByVal  
      int[] array1 = new int[ 10 ];
      Console.WriteLine( "Integer array passed ByVal before call:" );
      for( int i = 0; i < array1.Length; i++ )
      {
         array1[ i ] = i;
         Console.Write( " " + array1[ i ] );
      }
      int sum1 = LibWrap.TestArrayOfInts( array1, array1.Length );
      Console.WriteLine( "\nSum of elements:" + sum1 );
      Console.WriteLine( "\nInteger array passed ByVal after call:" );

      foreach( int i in array1 )
      {
         Console.Write( " " + i );
      }   

      // array ByRef  
      int[] array2 = new int[ 10 ];
      int size = array2.Length;
      Console.WriteLine( "\n\nInteger array passed ByRef before call:" );
      for( int i = 0; i < array2.Length; i++ )
      {
         array2[ i ] = i;
         Console.Write( " " + array2[ i ] );
      }
      IntPtr buffer = Marshal.AllocCoTaskMem( Marshal.SizeOf( size ) 
         * array2.Length );
      Marshal.Copy( array2, 0, buffer, array2.Length );

      int sum2 = LibWrap.TestRefArrayOfInts( ref buffer, ref size );
      Console.WriteLine( "\nSum of elements:" + sum2 );
      if( size > 0 )
      {
         int[] arrayRes = new int[ size ];
         Marshal.Copy( buffer, arrayRes, 0, size );
         Marshal.FreeCoTaskMem( buffer );
         Console.WriteLine( "\nInteger array passed ByRef after call:" );
         foreach( int i in arrayRes )
         {
            Console.Write( " " + i );
         }
      }
      else
         Console.WriteLine( "\nArray after call is empty" );

      // matrix ByVal  
      const int DIM = 5;
      int[,] matrix = new int[ DIM, DIM ];

      Console.WriteLine( "\n\nMatrix before call:" );
      for( int i = 0; i < DIM; i++ )
      {
         for( int j = 0; j < DIM; j++ )
         {
            matrix[ i, j ] = j;
            Console.Write( " " + matrix[ i, j ] );
         }
         Console.WriteLine( "" );
      }
      int sum3 = LibWrap.TestMatrixOfInts( matrix, DIM );
      Console.WriteLine( "\nSum of elements:" + sum3 );
      Console.WriteLine( "\nMatrix after call:" );
      for( int i = 0; i < DIM; i++ )
      {
         for( int j = 0; j < DIM; j++ )
         {
            Console.Write( " " + matrix[ i, j ] );
         }
         Console.WriteLine( "" );
      }

      // string array ByVal 
      String[] strArray = { "one", "two", "three", "four", "five" };
      Console.WriteLine( "\n\nString array before call:" );
      foreach( String s in strArray )
         Console.Write( " "+ s );
      int lenSum = LibWrap.TestArrayOfStrings( strArray, strArray.Length );
      Console.WriteLine( "\nSum of string lengths:" + lenSum );
      Console.WriteLine( "\nString array after call:" );
      foreach( String s in strArray )
      {
         Console.Write( " " + s );
      }   

      // struct array ByVal 
      MyPoint[] points = { new MyPoint(1,1), new MyPoint(2,2), new MyPoint(3,3) };
      Console.WriteLine( "\n\nPoints array before call:" );
      foreach( MyPoint p in points )
         Console.WriteLine( "x = {0}, y = {1}", p.x, p.y );
      int allSum = LibWrap.TestArrayOfStructs( points, points.Length );
      Console.WriteLine( "\nSum of points:" + allSum );
      Console.WriteLine( "\nPoints array after call:" );
      foreach( MyPoint p in points )
         Console.WriteLine( "x = {0}, y = {1}", p.x, p.y );      

      // struct with strings array ByVal 
      MyPerson[] persons = { new MyPerson( "Kim", "Akers" ), 
      new MyPerson( "Adam", "Barr" ), new MyPerson( "Jo", "Brown" )};

      Console.WriteLine( "\n\nPersons array before call:" );
      foreach( MyPerson pe in persons )
        Console.WriteLine( "first = {0}, last = {1}", pe.first, pe.last );
      int namesSum = LibWrap.TestArrayOfStructs2( persons, persons.Length );
      Console.WriteLine( "\nSum of name lengths:" + namesSum );
      Console.WriteLine( "\n\nPersons array after call:" );
      foreach( MyPerson pe in persons )
        Console.WriteLine( "first = {0}, last = {1}", pe.first, pe.last );
   }
}