load a C dll in C# with dllimport

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Hi.
I Have A C dll That I Got From Another team in My project.
I Try to Load A Certain Function From it in C#
The function looks Like That:
Void GetData(TCHAR name [], char **address, DWORD *size)
How Should I declare The equivilant Function in C# ?
I am Using DllImport...
Thanks
Dj4400

Posted 26-May-13 22:32pm

dj4400

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zlogdan 28-May-13 13:49pm

I have had to marshal C code into C# in the past, it was not easy, but I left this question at this forum and it helped me: http://stackoverflow.com/questions/3264789/how-to-convert-a-void-to-a-type-that-can-be-used-in-c-interoperability-betwee

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dj4400 · Answer 1 · 2013-05-27T20:40:00

Solution 2

Using unsafe and char*.
The Function looks Like This:
public static extern void GetData(stringBuilder str, char **addr, uint *size)

Posted 27-May-13 20:40pm

dj4400

CzimerA · Answer 2 · 2013-05-29T22:56:00

I use to use this way call functions with pointer to pointer arguments. This may good for your function also.

The string and the string list would be used with int pointers:

C#

public static extern void GetData( System.IntPtr name, System.IntPtr address, ref Int32 Size)

before call alloc name:

C#

IntPtr name = Marshal.AllocHGlobal(Marshal.SystemDefaultCharSize * <maxsize>);

then call:

C#

GetData(ref name, ref address, ref Size);

you can get the Name and Address like this way:

C#

string Name = GlobalMarshaller.StringFromIntPtr(name);
string[] Adress = GlobalMarshaller.StringFromIntPtr(address, <maxcount>, <maxsize>);

Then clean up!

C#

Marshal.FreeHGlobal(name);
Marshal.FreeHGlobal(adress);

sjs4u · Answer 3 · 2013-05-26T23:23:00

Solution 1

Hi dj4400u,

Use

public static extern void GetData(stringbuilder sb,string,double);

Also make sure that your dll path is right.make it hardcoded path first and then try with runtime path.

Please let me know in case of any issue.

Thanks
sjs

Posted 26-May-13 23:23pm

sjs4u

Comments

Noel Jo 27-May-13 5:58am

yeah!

dj4400 27-May-13 8:54am

Its not working.... I Get An Acess Violation Exception
Attempted to Read or Write Protected Memory.
When Using The dll in c++ App i Declare:
TCHAR Str[260] And copy A string to it With strcpy
Char *addr[64] And DWORD Size[64]
The Call to the Dll Function Looks Like This:
GetData(Str ,&addr[i], &Size[i]);
Both Addr And size Are Global And dont Get A Value Before The Function Call

dj4400 27-May-13 10:58am

The dll function itself returns Addr Allocated and a Number In Size.
If i put a Break Point The Values That are send to the function
Are A "String" and 2 addresses The First One Points To A 'bad Pointer'

dj4400 27-May-13 10:58am

The second one points to zero

Richard MacCutchan 28-May-13 3:39am

How do you get a double from a DWORD*, or a string from a char**?