System.EntryPointNotFoundException：无法找到入口点

Question

I have convert VB6 to c# while executing it generate this error

FROM VB6

Declare Function OpenCommPort Lib "C:\Program Files\MR705API.dll" Alias "?OpenCommPort@@YGHPADPAPAX@Z" (ByVal PortName As String, ByRef hCom As Long) As Long
Declare Function CloseCommPort Lib "C:\Program Files\MR705API.dll" Alias "?CloseCommPort@@YGHPAX@Z" (ByVal hCom As Long) As Long
Declare Function SetLED Lib "C:\Program Files\MR705API.dll" Alias "?SetLED@@YGHPAXEE@Z" (ByVal hCom As Long, ByVal Led As Byte, ByVal Addr As Byte) As Long
Declare Function ActiveBuzzer Lib "C:\Program Files\MR705API.dll" Alias "?ActiveBuzzer@@YGHPAXEE@Z" (ByVal hCom As Long, ByVal DelayTime As Byte, ByVal Addr As Byte) As Long
Declare Function Iso14443Reqa Lib "C:\Program Files\MR705API.dll" Alias "?Iso14443Reqa@@YGHPAXEPAEE@Z" (ByVal hCom As Long, ByVal ReqAMode As Byte, ByVal ATQ As String, ByVal Addr As Byte) As Long
Declare Function Iso14443Anticoll Lib "C:\Program Files\MR705API.dll" Alias "?Iso14443Anticoll@@YGHPAXEPAE1E@Z" (ByVal hCom As Long, ByVal AnticollMode As Byte, ByVal Uid As String, ByVal MultiTag As String, ByVal Addr As Byte) As Long

IN C#

        [DllImport ("MR705API.dll")]
        public static extern long OpenCommPort(String portName, ref long hCom ); 

        [DllImport ("MR705API.dll")]
        public static extern long CloseCommPort(long hCom);

        [DllImport ("MR705API.dll")]
        public static extern long SetLED(long hCom, byte Led , byte Addr);

        [DllImport ("MR705API.dll")]
        public static extern long ActiveBuzzer (long hcom, byte DelayTime, byte Addr);

        [DllImport ("MR705API.dll")]
        public static extern long Iso14443Reqa (long hcom, byte ReqAMode, string ATQ, byte Addr);

And how I use it..

public void doReader() {

            Result = OpenCommPort("COM9", ref HANDLE);
            ....
            ....
}

Exception

System.EntryPointNotFoundException: Unable to find an entry point named 'OpenCommPort' in DLL 'MR705API.dll'.

   at TrueReader.MainForm.OpenCommPort(String portName, Int64& hCom)
   at TrueReader.MainForm.doReader() in c:\Users\sattha\Documents\SharpDevelop Projects\TrueReader\TrueReader\MainForm.cs:line 59
   at TrueReader.MainForm.Timer1Tick(Object sender, EventArgs e) in c:\Users\sattha\Documents\SharpDevelop Projects\TrueReader\TrueReader\MainForm.cs:line 54
   at System.Windows.Forms.Timer.OnTick(EventArgs e)
   at System.Windows.Forms.Timer.TimerNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.Run(Form mainForm)
   at TrueReader.Program.Main(String[] args) in c:\Users\sattha\Documents\SharpDevelop Projects\TrueReader\TrueReader\Program.cs:line 27

Can any one guide me, what did I do wrong?? or what did I miss.

I don't know how this .dll wrote and in which languages.

but it had used in VB6 before.

Answer 1

YOU SHOULD DEFINE ENTRY POINT FOR EACH DLLIMPORT FUNCTIONS

Just copy entry point from Alias from your VB6 code to C#

FOR EXAMPLE... "OpenCommPort" in VB6

Alias "?OpenCommPort@@YGHPADPAPAX@Z"

TO -> "OpenCommPort" in C#

[DllImport ("MR705API.dll",
EntryPoint="?OpenCommPort@@YGHPADPAPAX@Z")]
public static extern int OpenCommPort(string portName, ref int hCom); 

ADDINTIONAL

long in VB6 equivalent to int in C#