Call C DLL in C# with in/out pointers

[J.M.]

Hi,

I need help.

I want use this API

LIB_EXTERN_C LIB_API long STDCALL method(
long id,
const double *vIN,
double *vOUT);

I use this syntaxe in c#

[DllImport("LIB.dll", EntryPoint="_method@12")]
public static extern long method(long idMethode, ref double [] vIn,
ref double[] vOUT);

double [] vIn = new double[10];
double [] vOUT= new double[10];

Main.method(1, ref vIn, ref vOUT);

I receive no error but the results it's bad...
vIn.Length == 1 and vOUT.Length == 1 and containt no data.

Thanks

 

[Ben Voigt]

Hi,

I need help.

I want use this API

LIB_EXTERN_C LIB_API long STDCALL method(
long id,
const double *vIN,
double *vOUT);

I use this syntaxe in c#

[DllImport("LIB.dll", EntryPoint="_method@12")]
public static extern long method(long idMethode, ref double [] vIn,
ref double[] vOUT);

Arrays are already pass-by-reference, you should try without "ref". The
function will not be able to resize the array (how could it? It knows
nothing about memory allocation in .NET)

double [] vIn = new double[10];
double [] vOUT= new double[10];

Main.method(1, ref vIn, ref vOUT);

I receive no error but the results it's bad...
vIn.Length == 1 and vOUT.Length == 1 and containt no data.

Thanks

 

[J.M.]

If I removed the ref key word, I get no errors and no resizes on arrays
but the vOut array is empty.

Hi,

I need help.

I want use this API

LIB_EXTERN_C LIB_API long STDCALL method(
long id,
const double *vIN,
double *vOUT);

I use this syntaxe in c#

[DllImport("LIB.dll", EntryPoint="_method@12")]
public static extern long method(long idMethode, ref double [] vIn,
ref double[] vOUT);Arrays are already pass-by-reference, you should try without "ref". The

function will not be able to resize the array (how could it? It knows
nothing about memory allocation in .NET)

double [] vIn = new double[10];
double [] vOUT= new double[10];

Main.method(1, ref vIn, ref vOUT);

I receive no error but the results it's bad...
vIn.Length == 1 and vOUT.Length == 1 and containt no data.

Thanks

 

[Willy Denoyette [MVP]]

Hi,

I need help.

I want use this API

LIB_EXTERN_C LIB_API long STDCALL method(
long id,
const double *vIN,
double *vOUT);

I use this syntaxe in c#

[DllImport("LIB.dll", EntryPoint="_method@12")]
public static extern long method(long idMethode, ref double [] vIn,
ref double[] vOUT);

double [] vIn = new double[10];
double [] vOUT= new double[10];

Main.method(1, ref vIn, ref vOUT);

I receive no error but the results it's bad...
vIn.Length == 1 and vOUT.Length == 1 and containt no data.

Thanks

1. long in C# is 64 bit, long in C is 32 bit.
2. double *vOUT is a pointer to a double, you are passing a reference to an array which
results in extra dereferencing.

So your signature should look like....

public static extern int method(intidMethode, double [] vIn,
double[] vOUT);
and you should call it using...

Main.method(1, vIn, vOUT);

Willy.

 

[J.M.]

Thanks,

The function execute perfectly.

"long in C == int in C# " ;-)

Hi,

I need help.

I want use this API

LIB_EXTERN_C LIB_API long STDCALL method(
long id,
const double *vIN,
double *vOUT);

I use this syntaxe in c#

[DllImport("LIB.dll", EntryPoint="_method@12")]
public static extern long method(long idMethode, ref double [] vIn,
ref double[] vOUT);

double [] vIn = new double[10];
double [] vOUT= new double[10];

Main.method(1, ref vIn, ref vOUT);

I receive no error but the results it's bad...
vIn.Length == 1 and vOUT.Length == 1 and containt no data.

Thanks1. long inC#is 64 bit, long inCis 32 bit.

2. double *vOUT is apointerto a double, you are passing a reference to an array which
results in extra dereferencing.

So your signature should look like....

public static extern int method(intidMethode, double [] vIn,
double[] vOUT);
and you should call it using...

Main.method(1, vIn, vOUT);

Willy.