import clr
from MyDotNetProject import PythonInterop
from System.Collections.Generic import List
from System import Double

x = PythonInterop.GetDoubleList()
assert isinstance(x, List[Double])

######################## Copy operations #################################

# [Python.NET] Efficient copy of .NET Array to ctypes or numpy array.
# https://mail.python.org/pipermail/pythondotnet/2014-May/001525.html

def copyNumpyToDotNetArray(srcnparray, destdotnetarray):
    ''' Copies the content in a numpy array of any dimensions with dtype=float to a one-dimensional .NET array
    The number of elements in srcnpfloat must not exceed the size of destdotnetdouble
    
    @srcnpfloat: numpy array (any number of dimensions) with dtype=float
    @destdotnetdouble: Pre-allocated .NET Double Array object (via Array.CreateInstance(Double, n) or similar) to copy the numpy array content into
    '''
    if len(srcnparray.shape) == 1 and not srcnparray.dtype == bool:
        ptr = IntPtr.__overloads__[long](srcnparray.__array_interface__['data'][0])
        Marshal.Copy(ptr, destdotnetarray, 0, srcnparray.size)
    else:
        if not srcnparray.flags.c_contiguous:
            srcnparray = srcnparray.copy(order='C')
        assert srcnparray.flags.c_contiguous
        PythonInterop.CopyFromPointer(IntPtr.__overloads__[long](srcnparray.__array_interface__['data'][0]), destdotnetarray)

def copyDotNetArrayToNumpy(srcdotnetarray, destnparray):
    ''' Copies the content of a one-dimensional .NET array into a numpy array of any dimensions
    The number of elements in srcdotnetdouble and destnpfloat must match
    
    @srcdotnetdouble: One-dimensional .NET Array of Doubles (via Array.CreateInstance(Double, n) or similar) containing source data
    @destnpfloat: numpy array (any number of dimensions) to copy the source data into
    
    Use dest = np.empty(desiredShape, dtype=float) to preinitialize if creating a new variable
    '''
    if len(srcdotnetarray) == 1:
        ptr = IntPtr.__overloads__[long](destnparray.__array_interface__['data'][0])
        Marshal.Copy(srcdotnetarray, 0, ptr, srcdotnetarray.Length)
    else:
        PythonInterop.CopyToPointer(srcdotnetarray, IntPtr.__overloads__[long](destnparray.__array_interface__['data'][0]))

######################## Conversions to .NET #############################

def dotnetArrayOf(nparray):
    ''' Creates and returns a .NET Array that mirrors the provided numpy array
    
    @nparray: numpy array
    
    @Returns: .NET Array with element type matching nparray.dtype and identical dimensions with content that matches the provided numpy array
    '''
    dims = nparray.shape
    n = len(dims)
    dims_dn = Array.CreateInstance(Int32, n)
    for i in range(n):
        dims_dn[i] = Int32(dims[i])
    if nparray.dtype == float:
        dn = Array.CreateInstance(Double, dims_dn)
    elif nparray.dtype == int: #NOTE: this check is probably invalid in Python 3.x
        dn = Array.CreateInstance(Int64, dims_dn)
    elif nparray.dtype == np.int32:
        dn = Array.CreateInstance(Int32, dims_dn)
    elif nparray.dtype == np.bool:
        dn = Array.CreateInstance(Boolean, dims_dn)
    else:
        raise NotImplementedError("dotnetArrayOf does not yet support dtype=" + str(nparray.dtype))
    copyNumpyToDotNetArray(nparray, dn)
    return dn

######################## Conversions from .NET ###########################
    
def numpyArrayOf(dotnetarray):
    ''' Creates and returns a numpy Array that mirrors the provided .NET array
    
    @dotnetarray: .NET Array
    
    @Returns: numpy Array with dtype matching dotnetarray's element type, and identical dimensions with content that matches the provided .NET Array
    '''
    dims = np.empty(dotnetarray.Rank, dtype=int)
    for i in range(dotnetarray.Rank):
        dims[i] = dotnetarray.GetLength(i)
    type_dn = dotnetarray.GetType().GetElementType().Name
    if type_dn == 'Double':
        dtype = float
    elif type_dn == 'Int32':
        dtype = np.int32
    elif type_dn == 'Int64':
        dtype = int #NOTE: probably invalid in Python 3.x
    elif type_dn == 'Boolean':
        dtype = np.bool
    else:
        raise NotImplementedError("numpyArrayOf does not yet support .NET Arrays with " + str(type_dn) + " elements")
    nparray = np.empty(dims, dtype=dtype, order='C')
    copyDotNetArrayToNumpy(dotnetarray, nparray)
    return nparray

    public class PythonInterop
    {
        /// <summary>
        /// Copies data from a NumPy array to the destination .NET array
        /// </summary>
        /// <param name="pSource">Pointer to a NumPy array to copy from</param>
        /// <param name="dest">.NET array to be copied into</param>
        /// <remarks>This routine handles Boolean arrays in a special way because NumPy arrays have each element occupying 1 byte while .NET has them occupying 4 bytes</remarks>
		public static void CopyFromPointer(IntPtr pSource, Array dest)
        {
            Type elementType = dest.GetType().GetElementType();
            int sizeOfElement = Marshal.SizeOf(elementType);
            if (elementType == typeof(Boolean))
                sizeOfElement = 1;

            int byteCount = sizeOfElement;
            for (int i = 0; i < dest.Rank; i++)
            {
                byteCount *= dest.GetLength(i);
            }

            var gch = GCHandle.Alloc(dest);
            var tPtr = Marshal.UnsafeAddrOfPinnedArrayElement(dest, 0);
            MemCopy(pSource, tPtr, byteCount);
            gch.Free();
        }

        /// <summary>
        /// Copies data from a .NET array to a NumPy array
        /// </summary>
        /// <param name="source">.NET array to be copied from</param>
        /// <param name="pDest">Pointer to a NumPy array to copy into</param>
		public static void CopyToPointer(Array source, IntPtr pDest)
        {
            Type elementType = source.GetType().GetElementType();
            int sizeOfElement = Marshal.SizeOf(elementType);
            if (elementType == typeof(Boolean))
                sizeOfElement = 1;

            int byteCount = sizeOfElement;
            for (int i = 0; i < source.Rank; i++)
                byteCount *= source.GetLength(i);

            var gch = GCHandle.Alloc(source);
            var tPtr = Marshal.UnsafeAddrOfPinnedArrayElement(source, 0);
            MemCopy(tPtr, pDest, byteCount);
            gch.Free();
        }

        private static readonly int SIZEOFINT = Marshal.SizeOf(typeof(int));
        private static unsafe void MemCopy(IntPtr pSource, IntPtr pDest, int byteCount)
        {
            int count = byteCount / SIZEOFINT;
            int rest = byteCount % count;
            unchecked
            {
                int* ps = (int*)pSource.ToPointer(), pd = (int*)pDest.ToPointer();
                // Loop over the cnt in blocks of 4 bytes, 
                // copying an integer (4 bytes) at a time:
                for (int n = 0; n < count; n++)
                {
                    *pd = *ps;
                    pd++;
                    ps++;
                }
                // Complete the copy by moving any bytes that weren't moved in blocks of 4:
                if (rest > 0)
                {
                    byte* ps1 = (byte*)ps;
                    byte* pd1 = (byte*)pd;
                    for (int n = 0; n < rest; n++)
                    {
                        *pd1 = *ps1;
                        pd1++;
                        ps1++;
                    }
                }
            }
        }
    }

...
scope.Exec(
    "fig = plt.figure() \n" +
    "plt.plot(x[1:], y[1:]) \n"   //we can slice a numpy array
);
var fig = scope.Get("fig");
//fig.show(); //show the figure
plotdata = Matplotlib.SaveFigureToArray(fig, 200, "png"); //save the figure to a .NET array

Numpy to .NET converted 8388608 bytes in 4.231 +/- 1.812 ms (mean: 4.0 ns/ele)
.NET to Numpy converted 8388608 bytes in 3.461 +/- 1.200 ms (mean: 3.3 ns/ele)

import numpy as np
import ctypes
import clr, System
from System import Array, Int32
from System.Runtime.InteropServices import GCHandle, GCHandleType

_MAP_NP_NET = {
    np.dtype('float32'): System.Single,
    np.dtype('float64'): System.Double,
    np.dtype('int8')   : System.SByte,
    np.dtype('int16')  : System.Int16,
    np.dtype('int32')  : System.Int32,
    np.dtype('int64')  : System.Int64,
    np.dtype('uint8')  : System.Byte,
    np.dtype('uint16') : System.UInt16,
    np.dtype('uint32') : System.UInt32,
    np.dtype('uint64') : System.UInt64,
    np.dtype('bool')   : System.Boolean,
}
_MAP_NET_NP = {
    'Single' : np.dtype('float32'),
    'Double' : np.dtype('float64'),
    'SByte'  : np.dtype('int8'),
    'Int16'  : np.dtype('int16'), 
    'Int32'  : np.dtype('int32'),
    'Int64'  : np.dtype('int64'),
    'Byte'   : np.dtype('uint8'),
    'UInt16' : np.dtype('uint16'),
    'UInt32' : np.dtype('uint32'),
    'UInt64' : np.dtype('uint64'),
    'Boolean': np.dtype('bool'),
}

def asNumpyArray(netArray):
    '''
    Given a CLR `System.Array` returns a `numpy.ndarray`.  See _MAP_NET_NP for 
    the mapping of CLR types to Numpy dtypes.
    '''
    dims = np.empty(netArray.Rank, dtype=int)
    for I in range(netArray.Rank):
        dims[I] = netArray.GetLength(I)
    netType = netArray.GetType().GetElementType().Name

    try:
        npArray = np.empty(dims, order='C', dtype=_MAP_NET_NP[netType])
    except KeyError:
        raise NotImplementedError("asNumpyArray does not yet support System type {}".format(netType) )

    try: # Memmove 
        sourceHandle = GCHandle.Alloc(netArray, GCHandleType.Pinned)
        sourcePtr = sourceHandle.AddrOfPinnedObject().ToInt64()
        destPtr = npArray.__array_interface__['data'][0]
        ctypes.memmove(destPtr, sourcePtr, npArray.nbytes)
    finally:
        if sourceHandle.IsAllocated: sourceHandle.Free()
    return npArray

def asNetArray(npArray):
    '''
    Given a `numpy.ndarray` returns a CLR `System.Array`.  See _MAP_NP_NET for 
    the mapping of Numpy dtypes to CLR types.

    Note: `complex64` and `complex128` arrays are converted to `float32` 
    and `float64` arrays respectively with shape [m,n,...] -> [m,n,...,2]
    '''
    dims = npArray.shape
    dtype = npArray.dtype
    # For complex arrays, we must make a view of the array as its corresponding 
    # float type.
    if dtype == np.complex64:
        dtype = np.dtype('float32')
        dims.append(2)
        npArray = npArray.view(np.float32).reshape(dims)
    elif dtype == np.complex128:
        dtype = np.dtype('float64')
        dims.append(2)
        npArray = npArray.view(np.float64).reshape(dims)

    netDims = Array.CreateInstance(Int32, npArray.ndim)
    for I in range(npArray.ndim):
        netDims[I] = Int32(dims[I])
    
    if not npArray.flags.c_contiguous:
        npArray = npArray.copy(order='C')
    assert npArray.flags.c_contiguous

    try:
        netArray = Array.CreateInstance(_MAP_NP_NET[dtype], netDims)
    except KeyError:
        raise NotImplementedError("asNetArray does not yet support dtype {}".format(dtype))

    try: # Memmove 
        destHandle = GCHandle.Alloc(netArray, GCHandleType.Pinned)
        sourcePtr = npArray.__array_interface__['data'][0]
        destPtr = destHandle.AddrOfPinnedObject().ToInt64()
        ctypes.memmove(destPtr, sourcePtr, npArray.nbytes)
    finally:
        if destHandle.IsAllocated: destHandle.Free()
    return netArray

if __name__ == '__main__':
    from time import perf_counter
    import matplotlib.pyplot as plt
    import psutil

    tries = 1000
    foo = np.full([1024,1024], 2.5, dtype='float32')


    netMem = np.zeros(tries)
    t_asNet = np.zeros(tries)
    netFoo = asNetArray( foo ) # Lazy loading makes the first iteration very slow
    for I in range(tries):
        t0 = perf_counter()
        netFoo = asNetArray( foo )
        t_asNet[I] = perf_counter() - t0
        netMem[I] = psutil.virtual_memory().free / 2.0**20

    t_asNumpy = np.zeros(tries)
    numpyMem = np.zeros(tries)
    unNetFoo = asNumpyArray( netFoo ) # Lazy loading makes the first iteration very slow
    for I in range(tries):
        t0 = perf_counter()
        unNetFoo = asNumpyArray( netFoo )
        t_asNumpy[I] = perf_counter() - t0
        numpyMem[I] = psutil.virtual_memory().free / 2.0**20

    # Convert times to milliseconds
    t_asNet *= 1000
    t_asNumpy *= 1000
    np.testing.assert_array_almost_equal( unNetFoo, foo )
    print( "Numpy to .NET converted {} bytes in {:.3f} +/- {:.3f} ms (mean: {:.1f} ns/ele)".format( \
        foo.nbytes, t_asNet.mean(), t_asNet.std(), t_asNet.mean()/foo.size*1e6 ) )
    print( ".NET to Numpy converted {} bytes in {:.3f} +/- {:.3f} ms (mean: {:.1f} ns/ele)".format( \
        foo.nbytes, t_asNumpy.mean(), t_asNumpy.std(), t_asNumpy.mean()/foo.size*1e6 ) )

    plt.figure()
    plt.plot(np.arange(tries), netMem, '-', label='asNetArray')
    plt.plot(np.arange(tries), numpyMem, '-', label='asNumpyArray')
    plt.legend(loc='best')
    plt.ylabel('Free memory (MB)')
    plt.xlabel('Iteration')
    plt.show(block=True)

namespace MyNamespace
{
    public class MyListContainerClass
    {
        private List<double> _myList = new List<double>();

        public List<double> MyList
        {
            get { return _myList; }
        }
    }
}

my_test_class = MyNamespace.MyListContainerClass()
my_list = my_test_class.MyList

# throws exception
# my_list.Add(4)

my_list.append(4)
assert (len(my_list) == 1) # passes

my_list = my_test_class.MyList
assert (len(my_list) == 1) # fails!!!!!