C#總結（七）動態加載C++動態鏈接庫

C#調用C++ 鏈接庫的方式分為靜態調用和動態調用這兩種方式。靜態調用之前的文章里面都有介紹，使用.net 提供的DllImport 導入相關的C++ 庫即可。請看之前的文章，https://www.cnblogs.com/zhangweizhong/p/8119340.html 。

今天介紹動態調用的方法。很多時候，Dll庫的目錄可能是變化的，或是有些場景，需要根據具體的情況，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#中我們經常通過配置動態的調用托管Dll，那么是不是也可以這樣動態調用C++動態鏈接呢？
只要通過LoadLibrary, GetProcess, FreeLibrary這幾個函數是可以動態調用動態鏈接的（它們包含在kernel32.dll中）。

 

原理

LoadLibrary ( string lpFileName)：載入指定的動態鏈接庫，並將它映射到當前進程使用的地址空間。載入成功后即可訪問庫內保存的資源 ， 除了LoadLibrary 方法，還有一個類似的 LoadLibraryEx 方法。

GetProcAddress (int hModule, string lpProcName)：GetProcAddress函數檢索指定的動態鏈接庫(DLL)中的輸出庫函數地址。 如果函數調用成功，返回值是DLL中的輸出函數地址。 如果函數調用失敗，返回值是NULL。調用函數GetLastError ，得到具體的錯誤信息。

 

FreeLibrary ( int hModule)  ：釋放指定的動態鏈接庫，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>
        /// 通過非托管函數名轉換為對應的委托 , by jingzhongrong
        ///</summary>
        ///<param name="dllModule"> 通過 LoadLibrary 獲得的 DLL 句柄 </param>
        ///<param name="functionName"> 非托管函數名 </param>
        ///<param name="t"> 對應的委托類型 </param>
        ///<returns> 委托實例，可強制轉換為適當的委托類型 </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托
        ///</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  轉換成對應的委托
        ///</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，獲得函數指針，並且將指針封裝成C#中的委托。原因很簡單，C#中已經不能使用指針了，如下：

定義委托

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. 通過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);

 

 

最后

通過如上例子，我們可以在C#中動態或者靜態的調用C++寫的代碼了。