Question

I have a solution that has a c++ dll project(MsgHook.cpp) with a function:-

BOOL f_closeSEB()
{
    logg(fp, "\n\n");
    //TerminateProcess(hPiProcess->hProcess,0);
    SendMessage(hWndCaller,WM_DESTROY,NULL,NULL);
    logg(fp, "   SEB exit sequence, destroy window\n");
    //logg(fp, "Leave LLKeyboardHook() and return -1\n\n");
    return -1;
}

I am trying to call this function from my c# web services project in the following way:-

using System.Runtime.InteropServices;

    namespace closeSEB
    {
        partial class closeSEBService
        {
            /// <summary> 
            /// Required designer variable.
            /// </summary>
            private System.ComponentModel.IContainer components = null;

            public enum commands
            {
                CloseIt=255
            }

            /// <summary>
            /// Clean up any resources being used.
            /// </summary>
            /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
            protected override void Dispose(bool disposing)
            {
                if (disposing && (components != null))
                {
                    components.Dispose();
                }
                base.Dispose(disposing);
            }

            [DllImport("MsgHook.dll", SetLastError = true)]
            public static extern void runRTS(string serviceName);

             protected override void OnCustomCommand(int command)
            {
              base.OnCustomCommand(command);
              if (command == (int)commands.CloseIt)
              {
                //Code to call msghook closeSEB function
                  runRTS("closeSEBService");
                  f_closeSEB(); 
              }
            }
            #region Component Designer generated code

            /// <summary> 
            /// Required method for Designer support - do not modify 
            /// the contents of this method with the code editor.
            /// </summary>
            private void InitializeComponent()
            {
                // 
                // closeSEBService
                // 
                this.ServiceName = "Service1";

            }

            #endregion

        }
    }

But in the compiler, I am getting an error that the name f_closeSEB does not exit in current context. Is this not the correct way of calling the function defined in DLL file via C#?

Answer 1

You have to make sure of two things:

1. Write the DLLImport correctly like in the examples shown below

   [DllImport(“MsgHook.dll”, SetLastError = true)]
   public static extern bool f_closeSEB();

2. Make sure you compile the DLL “MsgHook.dll” for x86 or x64 according to the C# program needs. .NET supports any cpu but C++ does not, so make sure of the required type.

for more information, please consider the MSDN article on Calling Win32 DLLs in C# with P/Invoke.