InitializeEngine 函数

// 使用 FREngine.dll 的路径、您的 FineReader Engine 客户项目 ID，
// 以及（如适用）Online License 令牌路径和 Online License 密码初始化这些变量
wchar_t* FreDllPath;
wchar_t* CustomerProjectId;
wchar_t* LicensePath;  // 如果不使用 Online License，请将这些变量赋为空字符串
wchar_t* LicensePassword;
// FREngine.dll 的 HANDLE
static HMODULE libraryHandle = 0;
// 全局 FineReader Engine 对象。
FREngine::IEnginePtr Engine;
void LoadFREngine()
{
    if( Engine != 0 ) {
    // 已加载
    return;
    }
    // 第一步：加载 FREngine.dll
    if( libraryHandle == 0 ) {
        libraryHandle = LoadLibraryEx( FreDllPath, 0, LOAD_WITH_ALTERED_SEARCH_PATH );
        if( libraryHandle == 0 ) {
            throw L"Error while loading ABBYY FineReader Engine";
        }
    }
    // 第二步：获取 Engine 对象
    typedef HRESULT ( STDAPICALLTYPE* InitializeEngineFunc )( BSTR, BSTR, BSTR, BSTR, 
        BSTR, VARIANT_BOOL, FREngine::IEngine** );
    InitializeEngineFunc pInitializeEngine =
    ( InitializeEngineFunc )GetProcAddress( libraryHandle, "InitializeEngine" );
    if( pInitializeEngine == 0 || pInitializeEngine( CustomerProjectId, LicensePath, 
        LicensePassword, L"", L"", VARIANT_FALSE, &Engine ) != S_OK ) {
    UnloadFREngine();
    throw L"Error while loading ABBYY FineReader Engine";
    }
}

public class EngineLoader : IDisposable
{
    public EngineLoader()
    {
        // 使用 FREngine.dll 的完整路径、您的 Customer Project ID，
        // 以及（如适用）您的 Online License 令牌文件路径和 Online License 密码初始化这些变量
        string enginePath = "";
        string customerProjectId = "";
        string licensePath = "";
        string licensePassword = "";
        // 加载 FREngine.dll 库
        dllHandle = LoadLibraryEx(enginePath, IntPtr.Zero, LOAD_WITH_ALTERED_SEARCH_PATH);
           
        try
        {
            if (dllHandle == IntPtr.Zero)
            {
                throw new Exception("Can't load " + enginePath);
            }
            IntPtr initializeEnginePtr = GetProcAddress(dllHandle, "InitializeEngine");
            if (initializeEnginePtr == IntPtr.Zero)
            {
                throw new Exception("Can't find InitializeEngine function");
            }
            IntPtr deinitializeEnginePtr = GetProcAddress(dllHandle, "DeinitializeEngine");
            if (deinitializeEnginePtr == IntPtr.Zero)
            {
                throw new Exception("Can't find DeinitializeEngine function");
            }
            IntPtr dllCanUnloadNowPtr = GetProcAddress(dllHandle, "DllCanUnloadNow");
            if (dllCanUnloadNowPtr == IntPtr.Zero)
            {
                throw new Exception("Can't find DllCanUnloadNow function");
            }
            // 将指针转换为委托
            initializeEngine = (InitializeEngine)Marshal.GetDelegateForFunctionPointer(
                initializeEnginePtr, typeof(InitializeEngine));
            deinitializeEngine = (DeinitializeEngine)Marshal.GetDelegateForFunctionPointer(
                deinitializeEnginePtr, typeof(DeinitializeEngine));
            dllCanUnloadNow = (DllCanUnloadNow)Marshal.GetDelegateForFunctionPointer(
                dllCanUnloadNowPtr, typeof(DllCanUnloadNow));
            // 调用 InitializeEngine 函数 
            // 传入 Online License 令牌文件路径和 Online License 密码
            int hresult = initializeEngine(customerProjectId, licensePath, licensePassword, 
                "", "", false, ref engine);
            Marshal.ThrowExceptionForHR(hresult);
        }
        catch (Exception)
        {
            // 释放 FREngine.dll 库
            engine = null;
            // 在调用 FreeLibrary 之前清理所有对象
            GC.Collect();
            GC.WaitForPendingFinalizers();
            GC.Collect();
            FreeLibrary(dllHandle);
            dllHandle = IntPtr.Zero;
            initializeEngine = null;
            deinitializeEngine = null;
            dllCanUnloadNow = null;
            throw;
        }
    }
    // Kernel32.dll 函数
    [DllImport("kernel32.dll")]
    private static extern IntPtr LoadLibraryEx(string dllToLoad, IntPtr reserved, uint flags);
    private const uint LOAD_WITH_ALTERED_SEARCH_PATH = 0x00000008;
    [DllImport("kernel32.dll")]
    private static extern IntPtr GetProcAddress(IntPtr hModule, string procedureName);
    [DllImport("kernel32.dll")]
    private static extern bool FreeLibrary(IntPtr hModule);
    // FREngine.dll 函数
    [UnmanagedFunctionPointer(CallingConvention.StdCall, CharSet = CharSet.Unicode)]
    private delegate int InitializeEngine(string customerProjectId, string licensePath, 
        string licensePassword, string tempFolder, string dataFolder, bool isSharedCPUCoresMode, 
        ref FREngine.IEngine engine);
    [UnmanagedFunctionPointer(CallingConvention.StdCall)]
    private delegate int DeinitializeEngine();
    [UnmanagedFunctionPointer(CallingConvention.StdCall)]
    private delegate int DllCanUnloadNow();
    // 私有变量
    private FREngine.IEngine engine = null;
    // FREngine.dll 的 Handle
    private IntPtr dllHandle = IntPtr.Zero;
    private InitializeEngine initializeEngine = null;
    private DeinitializeEngine deinitializeEngine = null;
    private DllCanUnloadNow dllCanUnloadNow = null;
}