asked on 7/20/2008

Calling my C++ DLL in C# - not works

I have a DLL in C++ and one of it's export's definations is like this:

void __stdcall MyFunc (const char *in, LPSTR result, size_t n, int iMode, char *Password)

I can't get it working PROPERLY (it works but with strange charachters, strange errors, strange behaviors)...

I defined it's Call method in C# like this:

[DllImport("AESDLL.dll")]
private static extern void EncryptString(
String cData,
[MarshalAs(UnmanagedType.LPStr)] StringBuilder Output,
int nSize,
int iMode,
[MarshalAs(UnmanagedType.LPStr)] StringBuilder Password
);

I tried WITH 10 more methods, removed MarshalAS, not worked.

I tried Using String for all, not worked

I tried using StringBuilder for all not worked

Please advice, I get unrelated outputs...

My C++ DLL returns output in result variable. (LPSTR result - second variable)

Please advice, thanks from now!

.NET Programming C++C#

Last Comment

Minh Võ Công

5/6/2010

CSecurity

7/20/2008

ASKER

I should add that this defination worked well in VB6 for my DLL:

Private Declare Sub MyFunc Lib "MyDLL.dll" (ByVal cData As String, ByVal output As String, ByVal Size As Long, ByVal iMode As Integer, ByVal password As String)

Minh Võ Công

7/21/2008

if password is not change you can implement like:

[DllImport("AESDLL.dll",CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        private static extern void EncryptString(
            String cData,
            [MarshalAs(UnmanagedType.LPArray)]byte[] buffer,
            int nSize,
            int iMode,
            String pass
         );
const int MAX_SIZE = 1000000;
byte[] buffer = new byte[MAX_SIZE * 2];

Open in new window

ASKER CERTIFIED SOLUTION

Minh Võ Công

7/21/2008

THIS SOLUTION IS ONLY AVAILABLE TO MEMBERS.

View this solution by signing up for a free trial.

Members can start a 7-Day free trial and enjoy unlimited access to the platform.

See Pricing Options

Start Free Trial

CSecurity

7/21/2008

ASKER

WHat do you mean by buffer? My function uses String

void __stdcall MyFunc (const char *in, LPSTR result, size_t n, int iMode, char *Password)

Output is in result

Minh Võ Công

5/6/2010

You can retrieve string by:

string str = System.Text.ASCIIEncoding.ASCII.GetString(buffer );
or
string str = System.Text.UnicodeEncoding.Unicode.GetString(buffer );