Calling Delphi DLL in c# "“Attempted to read or write protected memory. " error

Question

I am trying to import a delphi dll and use its method.

Here is the delphi method signature:

function CALinkEncode(SubscriberID, MailshotID, LinkID: DWORD; sCode: PWideChar): HRESULT; stdcall;

Here is the c# code to import the dll and use the function.

    [DllImport(@"Decoder.dll", CharSet = CharSet.Ansi)]
    static extern string CALinkEncode(
        int SubscriberID,
        int MailshotID,
        int LinkID
    );

    public static string CALinkDecodeString(int cas, int cam, int cal)
    {
        string retvalptr = CALinkEncode(cas, cam, cal);

        return retvalptr;
    }

Please help.

David Heffernan · Accepted Answer · 2013-07-16 12:17:44Z

4

You are missing a parameter, have the wrong return type, and have the wrong character set. It should be:

[DllImport(@"Decoder.dll", CharSet = CharSet.Unicode)]
static extern uint CALinkEncode(
     uint SubscriberID,
     uint MailshotID,
     uint LinkID,
     string sCode
 );

I've assumed the string parameter is an input parameter. If not, then you need to declare it as StringBuilder and pass a StringBuilder instance with sufficient capacity for the output buffer.

.

edited Jul 16, 2013 at 12:17

answered Jul 16, 2013 at 10:52

David Heffernan

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