C# 调用C++ dll

        [DllImport("kernel32.dll", EntryPoint = "LoadLibrary", CallingConvention = CallingConvention.StdCall)]
        public static extern int LoadLibrary([MarshalAs(UnmanagedType.LPStr)] string lpLibFileName);

        [DllImport("kernel32.dll", EntryPoint = "GetProcAddress", CallingConvention = CallingConvention.StdCall)]
        public static extern IntPtr GetProcAddress(int hModule, [MarshalAs(UnmanagedType.LPStr)] string lpProcName);

        [DllImport("kernel32.dll", EntryPoint = "FreeLibrary", CallingConvention = CallingConvention.StdCall)]
        public static extern bool FreeLibrary(int hModule);

        /// <summary>
        /// 根据dll地址获取委托
        /// </summary>
        /// <param name="dllModule">调用 LoadLibrary后得到的int 值</param>
        /// <param name="functionName">在dll中约定的函数名称</param>
        /// <param name="t">接收dll约定函数的委托</param>
        /// <returns></returns>
        public static Delegate GetDelegateFromAddress(int dllModule, string functionName, Type t)
        {
            IntPtr address = GetProcAddress(dllModule, functionName);

            if (address == IntPtr.Zero)
                return null;

            return Marshal.GetDelegateForFunctionPointer(address, t);
        }

        /// <summary>
        /// 根据指针获取委托
        /// </summary>
        /// <param name="address"></param>
        /// <param name="t"></param>
        /// <returns></returns>
        public static Delegate GetDelegateFromIntPtr(IntPtr address, Type t)
        {
            if (address == IntPtr.Zero)
                return null;

            return Marshal.GetDelegateForFunctionPointer(address, t);
        }