Comparison Data Type VB vs VC++

[peeratep]

C++ library:
__declspec(dllexport) int WINAPI Caller(const char* username)

Vb code:
Private Declare Function Caller Lib "MyCaller.dll" () As Integer
dim i as integer

what! data type to by pass to caller function with correct using in c++
'i = Caller ("user1")


how to print log [const char* username] in c++, please suggest to me.

[hoxsiew]

Just and educated guess (been years since I've even seen VB code):

Private Declare Function Caller Lib "MyCaller.dll" (ByRef String) As Integer

[peeratep]

C++ library:
__declspec(dllexport) int WINAPI Caller(const wchar_t* username)

Vb code:
Private Declare Function Caller Lib "MyCaller.dll" () As Integer

in c++ library
use const wchar_t*

then in vb code what use


Thank you.

[hoxsiew]

I had a little free time on my lunch break so I decided to look into this.

As I mentioned upthread, I'm not at all familiar with VB and haven't even looked at any VB code in nearly 10 years, so a real VB programmer is likely to be able to come up with a more elegant solution.

First, the C++ dll needs the extern "C" declaration to prevent name mangling, so if you don't have the source for your DLL in question, you're probably screwed anyway.

The only way I could get this to work was to declare the VB dll export as taking a short array as it's parameter. Then I had to find a way to actually send a VB string as a short array which resulted in the function ToCString shown below (this was done in VS2008 so YMMV):

Public Class Form1
    Private Declare Function Caller Lib "..\..\..\..\Debug\VBwDLL.dll" (ByVal s As Short()) As Integer

    Private Function ToCString(ByVal s As String) As Short()
        Dim i As Integer
        Dim x As Integer
        Dim sarr() As Short

        i = s.Length()
        ReDim sarr(i)

        For x = 0 To i - 1
            sarr(x) = AscW(s.Substring(x, 1))
        Next
        sarr(x) = 0
        Return sarr

    End Function

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim i As Long

        i = Caller(ToCString("Hello World"))

        TextBox1.Text = i.ToString()
    End Sub
End Class

I've attached the whole solution including the test dll and a VB forms app to call the dll if you want to check it out.