I would greatly appreciate anyone that can help me with the proper way to
declare this interface?

Here is the C++ declaration:

interface IASIO : public IUnknown
{
    virtual ASIOBool init(void *sysHandle) = 0;
    virtual void getDriverName(char *name) = 0;   
    virtual long getDriverVersion() = 0;
    virtual void getErrorMessage(char *string) = 0;   
    virtual ASIOError start() = 0;
    virtual ASIOError stop() = 0;
    virtual ASIOError getChannels(long *numInputChannels, long
*numOutputChannels) = 0;
    virtual ASIOError getLatencies(long *inputLatency, long *outputLatency) = 0;
    virtual ASIOError getBufferSize(long *minSize, long *maxSize,
        long *preferredSize, long *granularity) = 0;
    virtual ASIOError canSampleRate(ASIOSampleRate sampleRate) = 0;
    virtual ASIOError getSampleRate(ASIOSampleRate *sampleRate) = 0;
    virtual ASIOError setSampleRate(ASIOSampleRate sampleRate) = 0;
    virtual ASIOError getClockSources(ASIOClockSource *clocks /* array */, long
*numSources) = 0;
    virtual ASIOError setClockSource(long reference) = 0;
    virtual ASIOError getSamplePosition(ASIOSamples *sPos, ASIOTimeStamp
*tStamp) = 0;
    virtual ASIOError getChannelInfo(ASIOChannelInfo *info) = 0;
    virtual ASIOError createBuffers(ASIOBufferInfo *bufferInfos, long
numChannels,
        long bufferSize, ASIOCallbacks *callbacks) = 0;
    virtual ASIOError disposeBuffers() = 0;
    virtual ASIOError controlPanel() = 0;
    virtual ASIOError future(long selector,void *opt) = 0;
    virtual ASIOError outputReady() = 0;
};

Here is what I have so far:

 [Guid("615C2C61-F8EB-11d3-B0B2-0000E8ED4AD9")]
   [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
   public interface IAsioDelta1010
   {
       AsioBool init(IntPtr sysHandle);        // void *
       void getDriverName(out String name);    // char *
       int getDriverVersion();
       void getErrorMessage(out String message);   // char *
       AsioError start();
       AsioError stop();
       AsioError getChannels(out int numInputChannels, out int
numOutputChannels);//  long *
       AsioError getLatencies(out int inputLatency, out int outputLatency);
//  long *
       AsioError getBufferSize(out int minSize, out int maxSize,
                               out int preferredSize, out int granularity);
  // long *
       AsioError canSampleRate(double sampleRate);
       AsioError getSampleRate(out double sampleRate); // double *
       AsioError setSampleRate(double sampleRate);
       AsioError getClockSources(ref AsioClockSource[] clocks, ref int
numSources);
       AsioError setClockSource(int reference);
       AsioError getSamplePosition(out AsioSamples sPos, out AsioTimeStamp
tStamp);
       AsioError getChannelInfo(ref AsioChannelInfo info);
       AsioError createBuffers(ref AsioBufferInfo[] bufferInfos, int
numChannels,
                               int bufferSize, ref AsioCallbacks callbacks);
       AsioError disposeBuffers();
       AsioError controlPanel();
       AsioError future(int selector, IntPtr opt); // void *
       AsioError outputReady();
   }

Here is my code to create the COM object:

Type AsioDelta1010 = Type.GetTypeFromCLSID(AsioGuid.Delta1010, true);
IAsioDelta1010 delta1010 =
(IAsioDelta1010)Activator.CreateInstance(AsioDelta1010);
delta1010.init(this.Handle); <<<--- this throws protected memory access
violation
int ver = delta1010.getDriverVersion();
Console.WriteLine(ver);

Here is the rest of the code I have converted thus far:

   public enum AsioBool : int
   {
       ASIOFalse = 0,
       ASIOTrue = 1
   }

   public enum AsioError : int
   {
       ASE_OK = 0,             // This value will be returned whenever the
call succeeded
       ASE_SUCCESS = 0x3f4847a0,    // unique success return value for ASIOFuture
calls
       ASE_NotPresent = -1000, // hardware input or output is not present or
available
       ASE_HWMalfunction,      // hardware is malfunctioning (can be returned
by any ASIO function)
       ASE_InvalidParameter,   // input parameter invalid
       ASE_InvalidMode,        // hardware is in a bad mode or used in a bad
mode
       ASE_SPNotAdvancing,     // hardware is not running when sample position
is inquired
       ASE_NoClock,            // sample clock or rate cannot be determined or
is not present
       ASE_NoMemory            // not enough memory for completing the request
   }

   public struct AsioClockSource
   {
       public int index;                    // as used for ASIOSetClockSource()
       public int associatedChannel;        // for instance, S/PDIF or AES/EBU
       public int associatedGroup;           // see channel groups
(ASIOGetChannelInfo())
       public AsioBool isCurrentSource;    // ASIOTrue if this is the current
clock source
       [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)]
       public string name;                   // for user selection
   }

   public struct AsioSamples
   {
        public uint hi;
       public uint lo;
    }

   public struct AsioTimeStamp
   {
       public uint hi;
       public uint lo;
   }

   public enum AsioSampleType : int
   {
       ASIOSTInt16MSB   = 0,
       ASIOSTInt24MSB   = 1,        // used for 20 bits as well
       ASIOSTInt32MSB   = 2,
       ASIOSTFloat32MSB = 3,        // IEEE 754 32 bit float
       ASIOSTFloat64MSB = 4,        // IEEE 754 64 bit double float
       // these are used for 32 bit data buffer, with different alignment of
the data inside
       // 32 bit PCI bus systems can be more easily used with these
       ASIOSTInt32MSB16 = 8,        // 32 bit data with 16 bit alignment
       ASIOSTInt32MSB18 = 9,        // 32 bit data with 18 bit alignment
       ASIOSTInt32MSB20 = 10,        // 32 bit data with 20 bit alignment
       ASIOSTInt32MSB24 = 11,        // 32 bit data with 24 bit alignment
       ASIOSTInt16LSB   = 16,
       ASIOSTInt24LSB   = 17,        // used for 20 bits as well
       ASIOSTInt32LSB   = 18,
       ASIOSTFloat32LSB = 19,        // IEEE 754 32 bit float, as found on Intel x86
architecture
       ASIOSTFloat64LSB = 20,         // IEEE 754 64 bit double float, as found on
Intel x86 architecture
       // these are used for 32 bit data buffer, with different alignment of
the data inside
       // 32 bit PCI bus systems can more easily used with these
       ASIOSTInt32LSB16 = 24,        // 32 bit data with 18 bit alignment
       ASIOSTInt32LSB18 = 25,        // 32 bit data with 18 bit alignment
       ASIOSTInt32LSB20 = 26,        // 32 bit data with 20 bit alignment
       ASIOSTInt32LSB24 = 27,        // 32 bit data with 24 bit alignment
       //    ASIO DSD format.
       ASIOSTDSDInt8LSB1   = 32,        // DSD 1 bit data, 8 samples per byte. First
sample in Least significant bit.
       ASIOSTDSDInt8MSB1   = 33,        // DSD 1 bit data, 8 samples per byte. First
sample in Most significant bit.
       ASIOSTDSDInt8NER8    = 40,        // DSD 8 bit data, 1 sample per byte. No
Endianness required.
       ASIOSTLastEntry
   }

   public struct AsioChannelInfo
   {
       public int channel;            // on input, channel index
       public AsioBool isInput;        // on input
       public AsioBool isActive;        // on exit
       public int channelGroup;        // dto
       public AsioSampleType type;    // dto
       [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
       public string name;                   // dto
   }

   public struct AsioBufferInfo
   {
       public AsioBool isInput;            // on input:  ASIOTrue: input, else output
       public int channelNum;            // on input:  channel index
       public IntPtr buffers1;            // on output: double buffer addresses
       public IntPtr buffers2;            // on output: double buffer addresses
   }

   public enum AsioTimeInfoFlags: uint
   {
       kSystemTimeValid        = 1,            // must always be valid
       kSamplePositionValid    = 1 << 1,       // must always be valid
       kSampleRateValid        = 1 << 2,
       kSpeedValid             = 1 << 3,
       kSampleRateChanged      = 1 << 4,
       kClockSourceChanged     = 1 << 5
   }

   public struct AsioTimeInfo
   {
       public double          speed;                  // absolute speed (1. =
nominal)
       public AsioTimeStamp systemTime;             // system time related
to samplePosition, in nanoseconds
                                               // on mac, must be derived from
Microseconds() (not UpTime()!)
                                               // on windows, must be derived
from timeGetTime()
       public AsioSamples samplePosition;
       public double sampleRate;             // current rate
       public uint flags;                    // (see below)
       [MarshalAs(UnmanagedType.ByValTStr, SizeConst=12)]
       public string reserved;                   // for user selection
   }

   public enum AsioTimeCodeFlags : uint
   {
       kTcValid                = 1,
       kTcRunning              = 1 << 1,
       kTcReverse              = 1 << 2,
       kTcOnspeed              = 1 << 3,
       kTcStill                = 1 << 4,
       kTcSpeedValid           = 1 << 8
   }

   public struct AsioTimeCode
   {      
       public double          speed;               // speed relation (fraction
of nominal speed)
                                                   // optional; set to 0. or
1. if not supported
       public AsioSamples timeCodeSamples;     // time in samples
       public uint flags;                          // some information flags
(see below)
       [MarshalAs(UnmanagedType.ByValTStr, SizeConst=64)]
       public string future;                       //
   }

   public struct AsioTime                  // both input/output
   {
       public int reserved1;               // must be 0
       public int reserved2;               // must be 0
       public int reserved3;               // must be 0
       public int reserved4;               // must be 0
       public AsioTimeInfo timeInfo;       // required
       public AsioTimeCode timeCode;       // optional, evaluated if
(timeCode.flags & kTcValid)
   }

   public enum AsioMessageSelectors: int
   {
       kAsioSelectorSupported = 1,    // selector in <value>, returns 1L if
supported,
                                   // 0 otherwise
       kAsioEngineVersion,            // returns engine (host) asio implementation
version,
                                   // 2 or higher
       kAsioResetRequest,            // request driver reset. if accepted, this
                                   // will close the driver (ASIO_Exit() ) and
                                   // re-open it again (ASIO_Init() etc). some
                                   // drivers need to reconfigure for instance
                                   // when the sample rate changes, or some basic
                                   // changes have been made in ASIO_ControlPanel().
                                   // returns 1L; note the request is merely passed
                                   // to the application, there is no way to determine
                                   // if it gets accepted at this time (but it usually
                                   // will be).
       kAsioBufferSizeChange,        // not yet supported, will currently always
return 0L.
                                   // for now, use kAsioResetRequest instead.
                                   // once implemented, the new buffer size is expected
                                   // in <value>, and on success returns 1L
       kAsioResyncRequest,            // the driver went out of sync, such that
                                   // the timestamp is no longer valid. this
                                   // is a request to re-start the engine and
                                   // slave devices (sequencer). returns 1 for ok,
                                   // 0 if not supported.
       kAsioLatenciesChanged,         // the drivers latencies have changed. The
engine
                                   // will refetch the latencies.
       kAsioSupportsTimeInfo,        // if host returns true here, it will expect the
                                   // callback bufferSwitchTimeInfo to be called instead
                                   // of bufferSwitch
       kAsioSupportsTimeCode,        //
       kAsioMMCCommand,            // unused - value: number of commands, message
points to mmc commands
       kAsioSupportsInputMonitor,    // kAsioSupportsXXX return 1 if host
supports this
       kAsioSupportsInputGain,     // unused and undefined
       kAsioSupportsInputMeter,    // unused and undefined
       kAsioSupportsOutputGain,    // unused and undefined
       kAsioSupportsOutputMeter,   // unused and undefined
       kAsioOverload,              // driver detected an overload
       kAsioNumMessageSelectors
   }

   public delegate void AsioBufferSwitchDelegate(int doubleBufferIndex,
AsioBool directProcess);
   public delegate void AsioSampleRateDidChangeDelegate(double sRate);
   public delegate void AsioMessageDelegate(int selector, int value, IntPtr
message, ref double opt);
   public delegate AsioTime AsioBufferSwitchTimeInfoDelegate(ref AsioTime
times, int doubleBufferIndex, AsioBool directProcess);

   public struct AsioCallbacks
   {
       public AsioBufferSwitchDelegate BufferSwitch;
       //void (*bufferSwitch) (long doubleBufferIndex, ASIOBool directProcess);
        // bufferSwitch indicates that both input and output are to be processed.
        // the current buffer half index (0 for A, 1 for B) determines
        // - the output buffer that the host should start to fill. the other buffer
        //   will be passed to output hardware regardless of whether it got filled
        //   in time or not.
        // - the input buffer that is now filled with incoming data. Note that
        //   because of the synchronicity of i/o, the input always has at
        //   least one buffer latency in relation to the output.
        // directProcess suggests to the host whether it should immedeately
        // start processing (directProcess == ASIOTrue), or whether its process
        // should be deferred because the call comes from a very low level
        // (for instance, a high level priority interrupt), and direct processing
        // would cause timing instabilities for the rest of the system. If in doubt,
        // directProcess should be set to ASIOFalse.
        // Note: bufferSwitch may be called at interrupt time for highest
efficiency.

       public AsioSampleRateDidChangeDelegate SampleRateDidChange;
       //void (*sampleRateDidChange) (ASIOSampleRate sRate);
        // gets called when the AudioStreamIO detects a sample rate change
        // If sample rate is unknown, 0 is passed (for instance, clock loss
        // when externally synchronized).

       public AsioMessageDelegate Message;
       //long (*asioMessage) (long selector, long value, void* message,
double* opt);
        // generic callback for various purposes, see selectors below.
        // note this is only present if the asio version is 2 or higher

       public AsioBufferSwitchTimeInfoDelegate BufferSwitchTimeInfo;
       //ASIOTime* (*bufferSwitchTimeInfo) (ASIOTime* params, long
doubleBufferIndex, ASIOBool directProcess);
        // new callback with time info. makes ASIOGetSamplePosition() and various
        // calls to ASIOGetSampleRate obsolete,
        // and allows for timecode sync etc. to be preferred; will be used if
        // the driver calls asioMessage with selector kAsioSupportsTimeInfo.
   }