Call c/c++ dll from c#/vb.net¶

string parameter¶

//void foo(const char *par);
<DllImport(MyDLL, CallingConvention:=CallingConvention.Cdecl, CharSet:=CharSet.Unicode)>
Shared Sub foo(<MarshalAsAttribute(UnmanagedType.LPStr)> ByVal par As String)
End Sub

return string¶

Shared Function foo() As IntPtr End Function Dim pRet As IntPtr = foo() Dim sRet As String = Marshal.PtrToStringAnsi(pRet) Dim sRet As String = Marshal.PtrToStringAuto(pRet) ‘ Unix

” vector parameter void foo(const int par[]); Shared Sub foo(ByVal par() As Integer) End Sub

” structure parameter ‘typedef struct { ‘ int x; ‘ double y[2]; ‘} struc1;

Structure struc1 Public x As Integer [MarshalAs(UnmanagedType.ByValArray, SizeConst:=2)] Public y() as Double End Structure

‘void foo(struc1 *par); Shared Sub foo(ByRef par As struc1) End Sub

Dim myStruc as struc1 = new struc1() myStruc.x = 1 myStruc.y = new Double(1) myStruc.y(0) = 1.0 myStruc.y(1) = 4.0 foo(myStruc)

” return structure ‘struc1* foo(void); Shared Function foo() As IntPtr End Function Dim pRet = foo()

” callback function ‘void setCallback(int (func)(void handle, const char *msg)); Delegate Function MyCallBack(ByVal handle As IntPtr, ByVal msg As StringBuilder) As Integer Shared Sub setCallBack(ByVal callbackfunc As MyCallBack) End Sub Private Function MyCallBackFunc(ByVal handle As IntPtr, ByVal msg As StringBuilder) As Integer Console.WriteLine(msg.ToString.Trim) Return 1 End Function logFunc = New MyCallBack(AddressOf MyCallackFunc) setCallBack(logFunc)

Please also check for other examples at: https://docs.microsoft.com/en-us/dotnet/framework/interop/marshaling-classes-structures-and-unions