exporting a struct with an array from a C++ dll to be accessed in C#

[AM]

Hi,
I have a C++ Dll that has a function that is being exported as
shown below

extern "C" __declspec(dllexport) validationResult __stdcall
_validateData(double dataToMat[], int time);

A structure is defined in the header(.h file) as shown below
struct validationResult
{
int rWaveValid; //validity of the WAVE
int signalStatusArray[4]; //validity of each of the channel data -
'causing the problems'
};

I need to call the above method from C# in where i have the following
structure defined
public struct validationResult
{
public int micDataValid; //validity of the microphone data
public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
channel data
};

And my function call is as shown
validationResult res = new validationResult();
res.signalStatusArray = new int[4];
res = _validateData(dataToMat, 2);

When the last line is reached i get an exception that says"Method's
type signature is not PInvoke compatible"
What am I doing wrong.

I know the issue is at the array inside the struct, as when I remove
the array from the C++ struct and the C# struct I get the right
response.

Thanks in Advance.
abhi M

 

[Ben Voigt]

Hi,
I have a C++ Dll that has a function that is being exported as
shown below

extern "C" __declspec(dllexport) validationResult __stdcall
_validateData(double dataToMat[], int time);

A structure is defined in the header(.h file) as shown below
struct validationResult
{
int rWaveValid; //validity of the WAVE
int signalStatusArray[4]; //validity of each of the channel data -
'causing the problems'
};

I need to call the above method from C# in where i have the following
structure defined
public struct validationResult
{
public int micDataValid; //validity of the microphone data

magically appeared?

public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
channel data

No, that doesn't match. A dynamically resizeable array is not the same as
an inline array of size 4. Look for the 'fixed' keyword in the C# help.

};

And my function call is as shown
validationResult res = new validationResult();
res.signalStatusArray = new int[4];
res = _validateData(dataToMat, 2);

When the last line is reached i get an exception that says"Method's
type signature is not PInvoke compatible"
What am I doing wrong.

I know the issue is at the array inside the struct, as when I remove
the array from the C++ struct and the C# struct I get the right
response.

Thanks in Advance.
abhi M

 

[AM]

I guess i did not copy my code correctly.
Here is what my C# struct looks like

public struct validationResult
{
public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
//channel data
};

Are you suggesting that the the error is caused by my array definition
in C# is dynamic (because of the []), while my C++ array is of size 4?

Hi,
I have a C++ Dll that has a function that is being exported as
shown below

extern "C" __declspec(dllexport) validationResult __stdcall
_validateData(double dataToMat[], int time);

A structure is defined in the header(.h file) as shown below
struct validationResult
{
int rWaveValid; //validity of the WAVE
int signalStatusArray[4]; //validity of each of the channel data -
'causing the problems'
};

I need to call the above method from C# in where i have the following
structure defined
public struct validationResult
{
public int micDataValid; //validity of the microphone data

magically appeared?

public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
channel data

No, that doesn't match. A dynamically resizeable array is not the same as
an inline array of size 4. Look for the 'fixed' keyword in the C# help.

};

And my function call is as shown
validationResult res = new validationResult();
res.signalStatusArray = new int[4];
res = _validateData(dataToMat, 2);

When the last line is reached i get an exception that says"Method's
type signature is not PInvoke compatible"
What am I doing wrong.

I know the issue is at the array inside the struct, as when I remove
the array from the C++ struct and the C# struct I get the right
response.

Thanks in Advance.
abhi M

 

[Willy Denoyette [MVP]]

I guess i did not copy my code correctly.
Here is what my C# struct looks like

public struct validationResult
{
public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
//channel data
};

Are you suggesting that the the error is caused by my array definition
in C# is dynamic (because of the []), while my C++ array is of size 4?

Hard to tell, as you did not post the function declaration (C#), also I'm not clear on why
you allocate a managed array in C# while your C function returns a pointer (to an array in
unmanaged memory).

res.signalStatusArray = new int[4]; // WHY????
res = _validateData(dataToMat, 2); //res is returned from C, it's a pointer right???

I would suggest you to post a complete sample that illustrates the issue.


Willy.

 

[AM]

Here is my C++ code

#include "CppMatlabWrapper.h"
#include <exception>
#include <string>
using namespace std;

//Method to validate the data
extern "C" __declspec(dllexport) validationResult __stdcall
_validateData(double dataToMat[], int time)
{
validationResult res;
res.signalStatusArray[0]=1;
res.signalStatusArray[1]=2;
res.signalStatusArray[2]=3;
res.signalStatusArray[3]=4;
res.micDataValid = (int)(dataToMat[0]*100);
res.rWaveValid = (int)(dataToMat[1]*100);
return res;
}

------------
Here is the header file CppMatlabWrapper.h
//Structure to store the result of the validation operation
struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
int signalStatusArray[4]; //validity of each of the channel data
};
extern "C" __declspec(dllexport) validationResult __stdcall
_validateData(double dataToMat[], int time);

This C++ code compiled gives me the library "CppMatlabWrapper.dll"
--------------------------------------------------------------------

Here is the C# code to access this library
using System;
using System.Runtime.InteropServices;

namespace MatlabWrapper
{
class Program
{

//Structure to receive the result of the validation operation
public struct validationResult
{
public int micDataValid; //validity of the microphone data
public int rWaveValid; //validity of the r Wave
public fixed int signalStatusArray[4];
};

[DllImport("CppMatlabWrapper.dll")]
static extern validationResult _validateData(double[] data,
int time);

static void Main(string[] args)
{
//code for creating a double array called dataToMat of
some size
//
validationResult res;
res = _validateData(dataToMat, 2);
}
}
}


THANKS
________

I guess i did not copy my code correctly.
Here is what my C# struct looks like

public struct validationResult
{
public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
//channel data
};

Are you suggesting that the the error is caused by my array definition
in C# is dynamic (because of the []), while my C++ array is of size 4?

Hard to tell, as you did not post the function declaration (C#), also I'm not clear on why
you allocate a managed array in C# while your C function returns a pointer (to an array in
unmanaged memory).

res.signalStatusArray = new int[4]; // WHY????
res = _validateData(dataToMat, 2); //res is returned from C, it's a pointer right???

I would suggest you to post a complete sample that illustrates the issue.

Willy.

 

[Ben Voigt]

I guess i did not copy my code correctly.
Here is what my C# struct looks like

public struct validationResult
{
public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
//channel data
};

Are you suggesting that the the error is caused by my array definition
in C# is dynamic (because of the []), while my C++ array is of size 4?

I am suggesting looking at the documentation for C# fixed-size buffers which
is here: http://msdn2.microsoft.com/en-us/library/zycewsya(VS.80).aspx

A dynamic (.NET) array carries additional stuff with it like length.
Additionally, since .NET arrays are ref class, only a pointer is stored in
the structure. This is totally different from the layout used by the C++
structure definition you gave.

Hi,
I have a C++ Dll that has a function that is being exported as
shown below

extern "C" __declspec(dllexport) validationResult __stdcall
_validateData(double dataToMat[], int time);

A structure is defined in the header(.h file) as shown below
struct validationResult
{
int rWaveValid; //validity of the WAVE
int signalStatusArray[4]; //validity of each of the channel data -
'causing the problems'
};

I need to call the above method from C# in where i have the following
structure defined
public struct validationResult
{
public int micDataValid; //validity of the microphone data

magically appeared?

public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
channel data

No, that doesn't match. A dynamically resizeable array is not the same
as
an inline array of size 4. Look for the 'fixed' keyword in the C# help.

};

And my function call is as shown
validationResult res = new validationResult();
res.signalStatusArray = new int[4];
res = _validateData(dataToMat, 2);

When the last line is reached i get an exception that says"Method's
type signature is not PInvoke compatible"
What am I doing wrong.

I know the issue is at the array inside the struct, as when I remove
the array from the C++ struct and the C# struct I get the right
response.

Thanks in Advance.
abhi M

 

[AM]

In that case what should my C# definition look like for the
corresponding C++ definition mentioned below?

C++ struct
struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
int signalStatusArray[4]; //validity of each of the channel
data
};

Thanks

I guess i did not copy my code correctly.
Here is what my C# struct looks like

public struct validationResult
{
public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
//channel data
};

Are you suggesting that the the error is caused by my array definition
in C# is dynamic (because of the []), while my C++ array is of size 4?

I am suggesting looking at the documentation for C# fixed-size buffers which
is here:http://msdn2.microsoft.com/en-us/library/zycewsya(VS.80).aspx

A dynamic (.NET) array carries additional stuff with it like length.
Additionally, since .NET arrays are ref class, only a pointer is stored in
the structure. This is totally different from the layout used by the C++
structure definition you gave.

Hi,
I have a C++ Dll that has a function that is being exported as
shown below
extern "C" __declspec(dllexport) validationResult __stdcall
_validateData(double dataToMat[], int time);
A structure is defined in the header(.h file) as shown below
struct validationResult
{
int rWaveValid; //validity of the WAVE
int signalStatusArray[4]; //validity of each of the channel data -
'causing the problems'
};
I need to call the above method from C# in where i have the following
structure defined
public struct validationResult
{
public int micDataValid; //validity of the microphone data
magically appeared?
public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
channel data
No, that doesn't match. A dynamically resizeable array is not the same
as
an inline array of size 4. Look for the 'fixed' keyword in the C# help.
};
And my function call is as shown
validationResult res = new validationResult();
res.signalStatusArray = new int[4];
res = _validateData(dataToMat, 2);
When the last line is reached i get an exception that says"Method's
type signature is not PInvoke compatible"
What am I doing wrong.
I know the issue is at the array inside the struct, as when I remove
the array from the C++ struct and the C# struct I get the right
response.
Thanks in Advance.
abhi M

 

[Ben Voigt]

In that case what should my C# definition look like for the
corresponding C++ definition mentioned below?

C++ struct
struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
int signalStatusArray[4]; //validity of each of the channel
data
};

C# (not compile tested)

unsafe struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
fixed int signalStatusArray[4]; //validity of each of the channel
data
};

or

struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
int signalStatusArray_0; //validity of each of the channel data
int signalStatusArray_1;
int signalStatusArray_2;
int signalStatusArray_3;
};

Thanks

I guess i did not copy my code correctly.
Here is what my C# struct looks like

public struct validationResult
{
public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
//channel data
};

Are you suggesting that the the error is caused by my array definition
in C# is dynamic (because of the []), while my C++ array is of size 4?

I am suggesting looking at the documentation for C# fixed-size buffers
which
is here:http://msdn2.microsoft.com/en-us/library/zycewsya(VS.80).aspx

A dynamic (.NET) array carries additional stuff with it like length.
Additionally, since .NET arrays are ref class, only a pointer is stored
in
the structure. This is totally different from the layout used by the C++
structure definition you gave.

Hi,
I have a C++ Dll that has a function that is being exported as
shown below

extern "C" __declspec(dllexport) validationResult __stdcall
_validateData(double dataToMat[], int time);

A structure is defined in the header(.h file) as shown below
struct validationResult
{
int rWaveValid; //validity of the WAVE
int signalStatusArray[4]; //validity of each of the channel data -
'causing the problems'
};

I need to call the above method from C# in where i have the
following
structure defined
public struct validationResult
{
public int micDataValid; //validity of the microphone data

magically appeared?

public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
channel data

No, that doesn't match. A dynamically resizeable array is not the
same
as
an inline array of size 4. Look for the 'fixed' keyword in the C#
help.

};

And my function call is as shown
validationResult res = new validationResult();
res.signalStatusArray = new int[4];
res = _validateData(dataToMat, 2);

When the last line is reached i get an exception that says"Method's
type signature is not PInvoke compatible"
What am I doing wrong.

I know the issue is at the array inside the struct, as when I remove
the array from the C++ struct and the C# struct I get the right
response.

Thanks in Advance.
abhi M

 

[AM]

When I use the struct u suggested
unsafe struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
fixed int signalStatusArray[4]; //validity of each of the
channel
data

};
I get the following error.
Unable to find an entry point named '_validateData' in DLL
'CppMatlabWrapper.dll'.

This error goes away When i remove the array fro both the C++ and the
C# structs. So I think It has something to do with the way my array is
declared in the struct.

Thanks.

In that case what should my C# definition look like for the
corresponding C++ definition mentioned below?

C++ struct
struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
int signalStatusArray[4]; //validity of each of the channel
data
};

C# (not compile tested)

unsafe struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
fixed int signalStatusArray[4]; //validity of each of the channel
data

};

or

struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
int signalStatusArray_0; //validity of each of the channel data
int signalStatusArray_1;
int signalStatusArray_2;
int signalStatusArray_3;

};

Thanks

I guess i did not copy my code correctly.
Here is what my C# struct looks like
public struct validationResult
{
public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
//channel data
};
Are you suggesting that the the error is caused by my array definition
in C# is dynamic (because of the []), while my C++ array is of size 4?
I am suggesting looking at the documentation for C# fixed-size buffers
which
is here:http://msdn2.microsoft.com/en-us/library/zycewsya(VS.80).aspx
A dynamic (.NET) array carries additional stuff with it like length.
Additionally, since .NET arrays are ref class, only a pointer is stored
in
the structure. This is totally different from the layout used by the C++
structure definition you gave.

Hi,
I have a C++ Dll that has a function that is being exported as
shown below
extern "C" __declspec(dllexport) validationResult __stdcall
_validateData(double dataToMat[], int time);
A structure is defined in the header(.h file) as shown below
struct validationResult
{
int rWaveValid; //validity of the WAVE
int signalStatusArray[4]; //validity of each of the channel data -
'causing the problems'
};
I need to call the above method from C# in where i have the
following
structure defined
public struct validationResult
{
public int micDataValid; //validity of the microphone data
magically appeared?
public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
channel data
No, that doesn't match. A dynamically resizeable array is not the
same
as
an inline array of size 4. Look for the 'fixed' keyword in the C#
help.
};
And my function call is as shown
validationResult res = new validationResult();
res.signalStatusArray = new int[4];
res = _validateData(dataToMat, 2);
When the last line is reached i get an exception that says"Method's
type signature is not PInvoke compatible"
What am I doing wrong.
I know the issue is at the array inside the struct, as when I remove
the array from the C++ struct and the C# struct I get the right
response.
Thanks in Advance.
abhi M

 

[AM]

Just so you guys know, I found a solution to the problem at the MSDN
forums. Here is a listing of the code

Code - header file

Header file
//Structure to store the result of the validation operation
struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
int signalStatusArray[4]; //validity of each of the channel data -
causing the problems
};

extern "C" __declspec(dllexport) void __stdcall _validateData(double
dataToMat[], int time, validationResult *retval);


Code - CPP file

Cpp file
extern "C" __declspec(dllexport) void __stdcall _validateData(double
dataToMat[], int time, validationResult *retval)
{

retval->micDataValid = 10;
retval->rWaveValid =20;

retval->signalStatusArray[0] =1;
retval->signalStatusArray[1] =2;
retval->signalStatusArray[2] =3;
retval->signalStatusArray[3] =4;
return;
}


Code - C# code

Here is a listing of the C# code
class Program
{
unsafe struct validationResult
{
int micDataValid;
int rWaveValid;
fixed int signalStatusArray[4];
}
static void Main(string[] args)
{
validationResult res;
_validateData(dataToMat, 2,out res);

//assume dataToMat is an array with //
data already in it
}
}
----------------------------------

Thanks again.

When I use the struct u suggested
unsafe struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
fixed int signalStatusArray[4]; //validity of each of the
channel
data

};

I get the following error.
Unable to find an entry point named '_validateData' in DLL
'CppMatlabWrapper.dll'.

This error goes away When i remove the array fro both the C++ and the
C# structs. So I think It has something to do with the way my array is
declared in the struct.

Thanks.

news:[email protected]...

In that case what should my C# definition look like for the
corresponding C++ definition mentioned below?
C++ struct
struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
int signalStatusArray[4]; //validity of each of the channel
data
};

C# (not compile tested)

unsafe struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
fixed int signalStatusArray[4]; //validity of each of the channel
data

};

or

struct validationResult
{
int micDataValid; //validity of the microphone data
int rWaveValid; //validity of the r Wave
int signalStatusArray_0; //validity of each of the channel data
int signalStatusArray_1;
int signalStatusArray_2;
int signalStatusArray_3;

};

Thanks

I guess i did not copy my code correctly.
Here is what my C# struct looks like
public struct validationResult
{
public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
//channel data
};
Are you suggesting that the the error is caused by my array definition
in C# is dynamic (because of the []), while my C++ array is of size 4?
I am suggesting looking at the documentation for C# fixed-size buffers
which
is here:http://msdn2.microsoft.com/en-us/library/zycewsya(VS.80).aspx
A dynamic (.NET) array carries additional stuff with it like length.
Additionally, since .NET arrays are ref class, only a pointer is stored
in
the structure. This is totally different from the layout used by the C++
structure definition you gave.

Hi,
I have a C++ Dll that has a function that is being exported as
shown below
extern "C" __declspec(dllexport) validationResult __stdcall
_validateData(double dataToMat[], int time);
A structure is defined in the header(.h file) as shown below
struct validationResult
{
int rWaveValid; //validity of the WAVE
int signalStatusArray[4]; //validity of each of the channel data -
'causing the problems'
};
I need to call the above method from C# in where i have the
following
structure defined
public struct validationResult
{
public int micDataValid; //validity of the microphone data
magically appeared?
public int rWaveValid; //validity of the r Wave
public int[] signalStatusArray; //validity of each of the
channel data
No, that doesn't match. A dynamically resizeable array is not the
same
as
an inline array of size 4. Look for the 'fixed' keyword in the C#
help.
};
And my function call is as shown
validationResult res = new validationResult();
res.signalStatusArray = new int[4];
res = _validateData(dataToMat, 2);
When the last line is reached i get an exception that says"Method's
type signature is not PInvoke compatible"
What am I doing wrong.
I know the issue is at the array inside the struct, as when I remove
the array from the C++ struct and the C# struct I get the right
response.
Thanks in Advance.
abhi M