C#總結（七）動態加載C++動態連接庫

 

C#調用C++ 連接庫的方式分爲靜態調用和動態調用這兩種方式。靜態調用以前的文章裏面都有介紹，使用.net 提供的DllImport 導入相關的C++ 庫便可。請看以前的文章，https://www.cnblogs.com/zhangweizhong/p/8119340.html 。

今天介紹動態調用的方法。不少時候，Dll庫的目錄多是變化的，或是有些場景，須要根據具體的狀況，來動態加載這些Dll庫。這樣使用靜態調用的方式就很不方便，C#中咱們常常經過配置動態的調用託管Dll，那麼是否是也能夠這樣動態調用C++動態連接呢？
只要經過LoadLibrary, GetProcess, FreeLibrary這幾個函數是能夠動態調用動態連接的（它們包含在kernel32.dll中）。

 

原理

LoadLibrary ( string lpFileName)：載入指定的動態連接庫，並將它映射到當前進程使用的地址空間。載入成功後便可訪問庫內保存的資源 ， 除了LoadLibrary 方法，還有一個相似的 LoadLibraryEx 方法。

GetProcAddress (int hModule, string lpProcName)：GetProcAddress函數檢索指定的動態連接庫(DLL)中的輸出庫函數地址。 若是函數調用成功，返回值是DLL中的輸出函數地址。 若是函數調用失敗，返回值是NULL。調用函數GetLastError ，獲得具體的錯誤信息。

 

FreeLibrary ( int hModule)  ：釋放指定的動態連接庫，它們早先是用LoadLibrary API函數裝載的。

 

GetLastError() ： 獲取錯誤信息

 

實現

 

1. 將kernel32中的幾個方法封裝成本地調用類 DLLWrapper

using System; using System.IO; using System.Runtime.InteropServices; namespace Irisking.Basic.Util { /// <summary>
    /// DLLWrapper /// </summary>
    internal class DLLWrapper { [DllImport("kernel32.dll")] private static extern uint GetLastError(); /// <summary>
        /// API LoadLibraryEx /// </summary>
        /// <param name="lpFileName"></param>
        /// <param name="hReservedNull"></param>
        /// <param name="dwFlags"></param>
        /// <returns></returns>
        [DllImport("kernel32.dll", EntryPoint = "LoadLibraryEx", SetLastError = true)] private static extern int LoadLibraryEx(string lpFileName, IntPtr hReservedNull, LoadLibraryFlags dwFlags); /// <summary>
        /// API GetProcAddress /// </summary>
        /// <param name="handle"></param>
        /// <param name="funcname"></param>
        /// <returns></returns>
        [DllImport("Kernel32", EntryPoint = "GetProcAddress", SetLastError = true)] public static extern int GetProcAddress(int handle, string funcname); /// <summary>
        /// API FreeLibrary /// </summary>
        /// <param name="handle"></param>
        /// <returns></returns>
        [DllImport("Kernel32", EntryPoint = "FreeLibrary", SetLastError = true)] private static extern int FreeLibrary(int handle); ///<summary>
        /// 經過非託管函數名轉換爲對應的委託 , by jingzhongrong ///</summary>
        ///<param name="dllModule"> 經過 LoadLibrary 得到的 DLL 句柄 </param>
        ///<param name="functionName"> 非託管函數名 </param>
        ///<param name="t"> 對應的委託類型 </param>
        ///<returns> 委託實例，可強制轉換爲適當的委託類型 </returns>
        public static Delegate GetFunctionAddress(int dllModule, string functionName, Type t) { int address = GetProcAddress(dllModule, functionName); if (address == 0) return null; else
                return Marshal.GetDelegateForFunctionPointer(new IntPtr(address), t); } ///<summary>
        /// 將表示函數地址的 intPtr 實例轉換成對應的委託 ///</summary>
        public static Delegate GetDelegateFromIntPtr(IntPtr address, Type t) { if (address == IntPtr.Zero) return null; else
                return Marshal.GetDelegateForFunctionPointer(address, t); } ///<summary>
        /// 將表示函數地址的 int 轉換成對應的委託 ///</summary>
        public static Delegate GetDelegateFromIntPtr(int address, Type t) { if (address == 0) return null; else
                return Marshal.GetDelegateForFunctionPointer(new IntPtr(address), t); } /// <summary>
        /// 加載sdk /// </summary>
        /// <param name="lpFileName"></param>
        /// <returns></returns>
        public static int LoadSDK(string lpFileName) { if (File.Exists(lpFileName)) { var hReservedNull = IntPtr.Zero; var dwFlags = LoadLibraryFlags.LOAD_WITH_ALTERED_SEARCH_PATH; var result = LoadLibraryEx(lpFileName, hReservedNull, dwFlags); var errCode = GetLastError(); LogHelper.Info($"LoadSDK Result:{result}, ErrorCode: {errCode}"); return result; } return 0; } /// <summary>
        /// 釋放sdk /// </summary>
        /// <param name="handle"></param>
        /// <returns></returns>
        public static int ReleaseSDK(int handle) { try { if (handle > 0) { LogHelper.Info($"FreeLibrary handle：{handle}"); var result = FreeLibrary(handle); var errCode = GetLastError(); LogHelper.Info($"FreeLibrary Result:{result}, ErrorCode: {errCode}"); return 0; } return -1; } catch (Exception ex) { LogHelper.Error(ex); return -1; } } } /// <summary>
    /// LoadLibraryFlags /// </summary>
    public enum LoadLibraryFlags : uint { /// <summary>
        /// DONT_RESOLVE_DLL_REFERENCES /// </summary>
        DONT_RESOLVE_DLL_REFERENCES = 0x00000001, /// <summary>
        /// LOAD_IGNORE_CODE_AUTHZ_LEVEL /// </summary>
        LOAD_IGNORE_CODE_AUTHZ_LEVEL = 0x00000010, /// <summary>
        /// LOAD_LIBRARY_AS_DATAFILE /// </summary>
        LOAD_LIBRARY_AS_DATAFILE = 0x00000002, /// <summary>
        /// LOAD_LIBRARY_AS_DATAFILE_EXCLUSIVE /// </summary>
        LOAD_LIBRARY_AS_DATAFILE_EXCLUSIVE = 0x00000040, /// <summary>
        /// LOAD_LIBRARY_AS_IMAGE_RESOURCE /// </summary>
        LOAD_LIBRARY_AS_IMAGE_RESOURCE = 0x00000020, /// <summary>
        /// LOAD_LIBRARY_SEARCH_APPLICATION_DIR /// </summary>
        LOAD_LIBRARY_SEARCH_APPLICATION_DIR = 0x00000200, /// <summary>
        /// LOAD_LIBRARY_SEARCH_DEFAULT_DIRS /// </summary>
        LOAD_LIBRARY_SEARCH_DEFAULT_DIRS = 0x00001000, /// <summary>
        /// LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR /// </summary>
        LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR = 0x00000100, /// <summary>
        /// LOAD_LIBRARY_SEARCH_SYSTEM32 /// </summary>
        LOAD_LIBRARY_SEARCH_SYSTEM32 = 0x00000800, /// <summary>
        /// LOAD_LIBRARY_SEARCH_USER_DIRS /// </summary>
        LOAD_LIBRARY_SEARCH_USER_DIRS = 0x00000400, /// <summary>
        /// LOAD_WITH_ALTERED_SEARCH_PATH /// </summary>
        LOAD_WITH_ALTERED_SEARCH_PATH = 0x00000008 } }

 

2. 使用DLLWrapper類動態讀取C++Dll，得到函數指針，而且將指針封裝成C#中的委託。緣由很簡單，C#中已經不能使用指針了，以下：

定義委託

UnmanagedFunctionPointer(CallingConvention.StdCall, CharSet = CharSet.Ansi)] public delegate int Delegate_IKUSBSDK_GetVersion([In] [Out] [MarshalAs(UnmanagedType.LPArray)] byte[] version);

 

 

3. 調用函數

//1. 加載sdk
var sdkModule = DLLWrapper.LoadSDK(_route.DeviceA_PATH); // 2. 經過handle 找到相關的函數
Delegate_IKUSBSDK_GetVersion getVersion = (Delegate_IKUSBSDK_GetVersion)DLLWrapper.GetFunctionAddress(sdkModule, "IKUSBSDK_GetVersion", typeof(Delegate_IKUSBSDK_GetVersion)); var result = getVersion(version);

 

 

最後

經過如上例子，咱們能夠在C#中動態或者靜態的調用C++寫的代碼了。

 

原文出處：https://www.cnblogs.com/zhangweizhong/p/10594422.html