一、DllImportAttribute

1、属性介绍

1 using System; 2 using System.Reflection; 3 using System.Security; 4  5 namespace System.Runtime.InteropServices 6 { 7     // Summary: 8     //     Indicates that the attributed method is exposed by an unmanaged dynamic-link 9     //     library (DLL) as a static entry point.10     [AttributeUsage(AttributeTargets.Method, Inherited = false)]11     [ComVisible(true)]12     public sealed class DllImportAttribute : Attribute13     {14         // Summary:15         //     Enables or disables best-fit mapping behavior when converting Unicode characters16         //     to ANSI characters.17         public bool BestFitMapping;18         //19         // Summary:20         //     Indicates the calling convention of an entry point.21         public CallingConvention CallingConvention;22         //23         // Summary:24         //     Indicates how to marshal string parameters to the method and controls name25         //     mangling.26         public CharSet CharSet;27         //28         // Summary:29         //     Indicates the name or ordinal of the DLL entry point to be called.30         public string EntryPoint;31         //32         // Summary:33         //     Controls whether the System.Runtime.InteropServices.DllImportAttribute.CharSet34         //     field causes the common language runtime to search an unmanaged DLL for entry-point35         //     names other than the one specified.36         public bool ExactSpelling;37         //38         // Summary:39         //     Indicates whether unmanaged methods that have HRESULT or retval return values40         //     are directly translated or whether HRESULT or retval return values are automatically41         //     converted to exceptions.42         public bool PreserveSig;43         //44         // Summary:45         //     Indicates whether the callee calls the SetLastError Win32 API function before46         //     returning from the attributed method.47         public bool SetLastError;48         //49         // Summary:50         //     Enables or disables the throwing of an exception on an unmappable Unicode51         //     character that is converted to an ANSI "?" character.52         public bool ThrowOnUnmappableChar;53 54         // Summary:55         //     Initializes a new instance of the System.Runtime.InteropServices.DllImportAttribute56         //     class with the name of the DLL containing the method to import.57         //58         // Parameters:59         //   dllName:60         //     The name of the DLL that contains the unmanaged method. This can include61         //     an assembly display name, if the DLL is included in an assembly.62         public DllImportAttribute(string dllName);63 64         // Summary:65         //     Gets the name of the DLL file that contains the entry point.66         //67         // Returns:68         //     The name of the DLL file that contains the entry point.69         public string Value { get; }70     }71 }

2、举例

1 class BLApi2 {3     [DllImport(@"xx.dll", EntryPoint = "TWelcomeFace_Init", ExactSpelling = false, CallingConvention = CallingConvention.Cdecl)]4     public extern static Int32 TWelcomeFace_Init(string namingService, string localhost, string dvsService, string matchService);5 }

 

3、引入依赖dll

将依赖dll添加到解决方案中，与主dll放在相同目录下（重要），然后设置dll的属性CopyToOutputDirectory= CopyAlways，编译器就会自动找到了。

二、应用LoadLibrary

1、封装基础类

1 public class DllInvoke 2     { 3         [DllImport("kernel32.dll")] 4         private extern static IntPtr LoadLibrary(String path); 5         [DllImport("kernel32.dll")] 6         private extern static IntPtr GetProcAddress(IntPtr lib, String funcName); 7         [DllImport("kernel32.dll")] 8         private extern static bool FreeLibrary(IntPtr lib); 9         [DllImport("kernel32.dll")]10         private extern static int GetLastError();11         private IntPtr hLib;12         public DllInvoke(String dllPath, List
     
       DependentDllPaths = null)13         {14             if(DependentDllPaths != null)15             {16                 foreach (string dllName in DependentDllPaths)17                 {18                     IntPtr loadAuxiliary = LoadLibrary(dllName);19                     if (loadAuxiliary == IntPtr.Zero)20                     {21                         throw new Exception(dllName + "加载失败！");22                     }23                 }24             }25             hLib = LoadLibrary(dllPath);26         }27         ~DllInvoke()28         {29             FreeLibrary(hLib);30         }31         32         public Delegate Invoke(String APIName, Type t)33         {34             IntPtr api = GetProcAddress(hLib, APIName);35             var s = Marshal.GetDelegateForFunctionPointer(api, t);36             return (Delegate)s;37         }38     }
     

LoadLibrary引用的dll相关的依赖dll必须被手动引用进来，否则会报错。

2、举例

1 [UnmanagedFunctionPointer(CallingConvention.Cdecl, CharSet = CharSet.Ansi, SetLastError = true)] 2     delegate Int32 TWelcomeFace_Init(string Naming_Service, string Locale_Host, string DVS_Service, string Match_Service); 3  4  class BLApi 5     { 6         private static DllInvoke _dll = new DllInvoke(@"xx.dll"); 7    8         public static Int32 TWelcomeFace_Init(string namingService, string localhost, string dvsService, string matchService) 9         {10             try11             {12                 TWelcomeFace_Init dele = (TWelcomeFace_Init)_dll.Invoke("TWelcomeFace_Init", typeof(TWelcomeFace_Init));13                 Int32 result = dele(namingService, localhost, dvsService, matchService);14 15                 return result;16             }17             catch (Exception ex)18             {19                 throw ex;20             }21         }22     }