Sharing multiple methods of accessing remote host resources in C#

最近要实现访问远程主机的共享目录中的一个文件。遇到了权限问题。google了一下，找到了几种解决方法，记录如下：
一、调用Net use命令

 // 使用方法：
        //if (Connect("192.168.1.48", "用户名", "密码"))   
        //{
        //    File.Copy(@"\\192.168.1.48\共享目录\test.txt",   @"e:\\test.txt",   true);   
        //}
        public bool Connect(string remoteHost, string userName, string passWord)
        {
            bool Flag = true;
            Process proc = new Process();
            proc.StartInfo.FileName = "cmd.exe";
            proc.StartInfo.UseShellExecute = false;
            proc.StartInfo.RedirectStandardInput = true;
            proc.StartInfo.RedirectStandardOutput = true;
            proc.StartInfo.RedirectStandardError = true;
            proc.StartInfo.CreateNoWindow = true;
            try
            {
                proc.Start();
                string command = @"net  use  \\" + remoteHost + "  " + passWord + "  " + "  /user:" + userName + ">NUL";
                proc.StandardInput.WriteLine(command);
                command = "exit";
                proc.StandardInput.WriteLine(command);
                while (proc.HasExited == false)
                {
                    proc.WaitForExit(1000);
                }
                string errormsg = proc.StandardError.ReadToEnd();
                if (errormsg != "")
                    Flag = false;
                proc.StandardError.Close();
            }
            catch (Exception ex)
            {
                Flag = false;
            }
            finally
            {
                proc.Close();
                proc.Dispose();
            }
            return Flag;
        }

二、调用WNetAddConnection2、WNetAddConnection3或者NetUseAdd函数，进行磁盘映射。

using System;using System.Collections.Generic;using System.Text;       using System.Runtime.InteropServices;
namespace WindowsApplication1{    public class MyMap    {        [DllImport("mpr.dll", EntryPoint = "WNetAddConnection2")]        public static extern uint WNetAddConnection2(            [In] NETRESOURCE lpNetResource,            string lpPassword,            string lpUsername,            uint dwFlags);                [DllImport("Mpr.dll")]        public static extern uint WNetCancelConnection2(            string lpName,            uint dwFlags,            bool fForce);                [StructLayout(LayoutKind.Sequential)]        public class NETRESOURCE        {            public int dwScope;            public int dwType;            public int dwDisplayType;            public int dwUsage;            public string LocalName;            public string RemoteName;            public string Comment;            public string Provider;        }
        // remoteNetworkPath format:  @"\\192.168.1.48\sharefolder"        // localDriveName format:     @"E:"        public static bool CreateMap(string userName, string password, string remoteNetworkPath, string localDriveName)        {                        NETRESOURCE myNetResource = new NETRESOURCE();            myNetResource.dwScope = 2;       //2:RESOURCE_GLOBALNET            myNetResource.dwType = 1;        //1:RESOURCETYPE_ANY            myNetResource.dwDisplayType = 3; //3:RESOURCEDISPLAYTYPE_GENERIC            myNetResource.dwUsage = 1;       //1: RESOURCEUSAGE_CONNECTABLE            myNetResource.LocalName = localDriveName;            myNetResource.RemoteName = remoteNetworkPath;            myNetResource.Provider = null;
            uint nret = WNetAddConnection2(myNetResource, password, userName, 0);
            if (nret == 0)                return true;            else                return false;        }
        // localDriveName format:     @"E:"        public static bool DeleteMap(string localDriveName)        {            uint nret = WNetCancelConnection2(localDriveName, 1, true);
            if (nret == 0)                return true;            else                return false;        }
        public void test()        {            // 注意：            // remote、local、username的格式一定要正确，否则可能出现错误            string remote = @"\\192.168.1.48\generals";            string local = @"P:";            string username = @"Domain\UserName";            string password = @"Password";            bool ret = MyMap.CreateMap(username, password, remote, local);            if (ret)            {                //do what you want:                // ...                //File.Copy("q:\\test.htm", "c:\\test.htm");
                MyMap.DeleteMap(local);            }        }    }}

三、使用WebClient类

由于WebClient类可以上传下载文件，并且支持以http:、https:和file:开头的URI，所以可以用WebClient类来传输文件。
添加System.Net命名空间后使用如下代码下载文件：

private void Test1()        {            try            {                WebClient client = new WebClient();                NetworkCredential cred = new NetworkCredential("username", "password", "172.16.0.222");                client.Credentials = cred;                client.DownloadFile("file://172.16.0.222/test/111.txt", "111.txt");            }            catch (Exception ex)            {                // 如果网络很慢，而文件又很大，这时可能有超时异常（Time out）。            }        }
        public void Test2()        {            try            {                WebClient client = new WebClient();                NetworkCredential cred = new NetworkCredential("username", "password", "domain");                client.Credentials = cred;                client.DownloadFile("file://172.16.0.222/test/111.txt", "111.txt");            }            catch (Exception ex)            {                // 如果网络很慢，而文件又很大，这时可能有超时异常（Time out）。            }        }

类似的还可以试试WebRequest、FileWebRequest等：

 WebRequest req = WebRequest.Create("file://138.12.12.14/generals/test.htm");
                NetworkCredential cred = new NetworkCredential("username", "password", "IP");
                req.Credentials = cred;
                WebResponse response = req.GetResponse();
                Stream strm = response.GetResponseStream();
                StreamReader r = new StreamReader(strm);
                ... ...

四、角色模拟

/// <summary>
    /// 身份模拟实现远程资源访问
    /// </summary>
    public class FileImpersonation
    {
        // logon types
        const int LOGON32_LOGON_INTERACTIVE = 2;
        const int LOGON32_LOGON_NETWORK = 3;
        const int LOGON32_LOGON_NEW_CREDENTIALS = 9;
        // logon providers
        const int LOGON32_PROVIDER_DEFAULT = 0;
        const int LOGON32_PROVIDER_WINNT50 = 3;
        const int LOGON32_PROVIDER_WINNT40 = 2;
        const int LOGON32_PROVIDER_WINNT35 = 1;
        [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern int LogonUser(string lpszUserName,
            string lpszDomain,
            string lpszPassword,
            int dwLogonType,
            int dwLogonProvider,
            ref IntPtr phToken);
        [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern int DuplicateToken(IntPtr hToken,
            int impersonationLevel,
            ref IntPtr hNewToken);
        [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern bool RevertToSelf();
        [DllImport("kernel32.dll", CharSet = CharSet.Auto)]
        public static extern bool CloseHandle(IntPtr handle);
        private WindowsImpersonationContext impersonationContext;
        /// <summary>
        /// 身份模拟
        /// </summary>
        /// <param name="userName">独立服务器用IP，域环境就用域名</param>
        /// <param name="domain"></param>
        /// <param name="password"></param>
        /// <returns></returns>
        public bool impersonateValidUser(string userName, string domain, string password)
        {
            WindowsIdentity tempWindowsIdentity;
            IntPtr token = IntPtr.Zero;
            IntPtr tokenDuplicate = IntPtr.Zero;
            if (RevertToSelf())
            {
                // 这里使用LOGON32_LOGON_NEW_CREDENTIALS来访问远程资源。
                // 如果要（通过模拟用户获得权限）实现服务器程序，访问本地授权数据库可
                // 以用LOGON32_LOGON_INTERACTIVE
                if (LogonUser(userName, domain, password, LOGON32_LOGON_NEW_CREDENTIALS,
                    LOGON32_PROVIDER_DEFAULT, ref token) != 0)
                {
                    if (DuplicateToken(token, 2, ref tokenDuplicate) != 0)
                    {
                        tempWindowsIdentity = new WindowsIdentity(tokenDuplicate);
                        impersonationContext = tempWindowsIdentity.Impersonate();
                        if (impersonationContext != null)
                        {
                            AppDomain.CurrentDomain.SetPrincipalPolicy(PrincipalPolicy.WindowsPrincipal);
                            IPrincipal pr = System.Threading.Thread.CurrentPrincipal;
                            IIdentity id = pr.Identity;
                            CloseHandle(token);
                            CloseHandle(tokenDuplicate);
                            return true;
                        }
                    }
                }
            }
            if (token != IntPtr.Zero)
                CloseHandle(token);
            if (tokenDuplicate != IntPtr.Zero)
                CloseHandle(tokenDuplicate);
            return false;
        }
        /// <summary>
        /// 取消模拟身份
        /// </summary>
        public void undoImpersonation()
        {
            impersonationContext.Undo();
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="domain">独立服务器用IP，域环境就用域名</param>
        /// <param name="username"></param>
        /// <param name="password"></param>
        /// <param name="act">需要执行的操作</param>
        public void ImpersonateFunc(string username, string domain, string password, Action act)
        {
            bool isImpersonated = false;
            try
            {
                if (impersonateValidUser(username, domain, password))
                {
                    isImpersonated = true;
                    //File.Copy(@"\\192.168.1.48\generals\now.htm", "c:\\now.htm", true);
                    act();
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
            finally
            {
                if (isImpersonated)
                    undoImpersonation();
            }
        }
        //
    }
 FileImpersonation imp = new FileImpersonation();
            imp.ImpersonateFunc("Administrator", "192.168.0.125", "xxxx", () =>
            {
                var source = new DirectoryInfo(@"D:\HR");
                string targetFolder = @"\\192.168.0.125\d$\HR";
                if (!Directory.Exists(targetFolder))
                {
                    Directory.CreateDirectory(targetFolder);
                }
                foreach (FileInfo item in source.GetFiles())
                {
                    string targertFile = Path.Combine(targetFolder, item.Name);
                    File.Copy(item.FullName, targertFile, true);
                }
            });

五、比较

方法一通过调用Shell命令Net Use实现，有点笨拙。
方法二和方法一有些相似之处。映射远程资源，然后访问。
方法三由于会有超时异常出现，所以在网络速度快、传输小文件时是可以的。
方法四通过身份模拟实现远程资源访问。一些服务器进程就是通过这种方式运行的。这种方法也是我的最爱。

六、要注意的地方

关于这几种方法，google后都可以找到一些文章。但是等到自己实际测试时，有时会出现各种小错误，
这些错误基本来源于两方面：

1、函数的参数选择有问题，和自己的环境不相符。
比如        

public static extern int LogonUser(String lpszUserName,
            String lpszDomain,
            String lpszPassword,
            int dwLogonType,
            int dwLogonProvider,
            ref IntPtr phToken);

中的dwLogonType，要访问远程资源就要用LOGON32_LOGON_NEW_CREDENTIALS，
要模拟本机用户就要用LOGON32_LOGON_INTERACTIVE。

2、函数的参数格式有问题。
    a、比如

 public static extern int LogonUser(String lpszUserName,
            String lpszDomain,
            String lpszPassword,
            int dwLogonType,
            int dwLogonProvider,
            ref IntPtr phToken);

    中的lpszUserName、lpszDomain、lpszPassword就要写清楚。

    我就在这遇到过问题，第一次测试时，远程服务器就是一台独立的文件服务器，这是我的调用方式：
        LogonUser("myname", "192.168.1.48", "password", LOGON32_LOGON_NEW_CREDENTIALS,
                    LOGON32_PROVIDER_DEFAULT, ref token);

    第二次测试时，远程服务器是域MyDomain中的一个成员服务器，提供文件服务。这时代码就应该是：

 LogonUser("myname", "MyDomain", "password", LOGON32_LOGON_NEW_CREDENTIALS,
                    LOGON32_PROVIDER_DEFAULT, ref token);

    注意，代码中是MyDomain而不是IP地址。

    b、再如：
    参考上面代码

 string remote = @"\\192.168.1.48\generals";
            string local = @"P:";
            string username = @"Domain\UserName";
            string password = @"Password";

    如果@"\\192.168.1.48\generals"变成@"\\192.168.1.48\generals\”就会出错；
    如果是域中的用户，那么把@"Domain\UserName"变成@"UserName"就会出错。

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