CODEWITHSUNDEEP
c#cdllimportaccess-violation
leonidas79
leonidas79

Reputation: 469

avoid AccessViolationException when calling c code

i am using c# to call a c code through a DLL , i got AccessViolationException when calling a method , here is the code from the source header

extern __declspec( dllexport )
int ReadCardSN( IN OUT unsigned char* CardSN );

in my c# code i am using 

public static byte[] Data = new byte[4];
[DllImport("CardLib.dll")]
public static extern Int32 ReadCardSN(byte[] Data);
int resCode = ReadCardSN(Data);

what can be the problem ?

Upvotes: 0

Views: 98

Answers (1)

David Heffernan
David Heffernan

Reputation: 613013

The error is because your buffer is too small. The example code shows the use of a buffer of length 10240. You supply a buffer of length 4.

As written it looks like the C code uses the default cdecl calling convention. Your C# code uses stdcall.

It would also be better to apply the [In, Out] attribute to the argument. Because byte[] is blittable that is not strictly necessary but it is semantically accurate.

Upvotes: 3

Related Questions