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;

example used webrequest

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

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.IO;

namespace Test
{
public class Test
{
// 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;

        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)
{
System.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;
}

        public void undoImpersonation()
{
impersonationContext.Undo();
}

        public void TestFunc()
{
bool isImpersonated = false;
try
{
if (impersonateValidUser("UserName", "Domain", "Password"))
{
isImpersonated = true;
//do what you want now, as the special user
// ...
File.Copy(@"//192.168.1.48/generals/now.htm", "c://now.htm", true);
}
}
finally
{
if (isImpersonated)
undoImpersonation();
}
}
}
}


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。