由于IIS的服务帐户往往没有权限,IO操作比较容易出问题,采用模拟登录
using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Xml.Linq;
using System.Security.Principal;
using System.Runtime.InteropServices;


using System.IO;

public partial class _Default : System.Web.UI.Page

...{
public const int LOGON32_LOGON_INTERACTIVE = 2;
public const int LOGON32_PROVIDER_DEFAULT = 0;
WindowsImpersonationContext impersonationContext;
[DllImport("advapi32.dll")]
public static extern int LogonUserA(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);


protected void Page_Load(object sender, EventArgs e)

...{

}
protected void button1_Click(object sender, EventArgs e)

...{
if (impersonateValidUser("test1", "contoso.local", "password01!"))

...{
//Insert your code that runs under the security context of a specific user here.
//button1.Text = "ok";

byte[] att = File.ReadAllBytes(@"/fileserver est1 est.txt");
string contentType = "application/octet-stream";
string filename = "test.txt";

Response.AppendHeader("Content-Disposition", "attachment;FileName=" + filename);
Response.AppendHeader("Content-Length", att.Length.ToString());

Response.BinaryWrite(att);
Response.Flush();

undoImpersonation();
}
else

...{
//Your impersonation failed. Therefore, include a fail-safe mechanism here.
}
}


private bool impersonateValidUser(String userName, String domain, String password)

...{
WindowsIdentity tempWindowsIdentity;
IntPtr token = IntPtr.Zero;
IntPtr tokenDuplicate = IntPtr.Zero;
if (RevertToSelf())

...{
if (LogonUserA(userName, domain, password, LOGON32_LOGON_INTERACTIVE,
LOGON32_PROVIDER_DEFAULT, ref token) != 0)

...{
if (DuplicateToken(token, 2, ref tokenDuplicate) != 0)

...{
tempWindowsIdentity = new WindowsIdentity(tokenDuplicate);
impersonationContext = tempWindowsIdentity.Impersonate();
if (impersonationContext != null)

...{
CloseHandle(token);
CloseHandle(tokenDuplicate);
return true;
}
}
}
}
if (token != IntPtr.Zero)
CloseHandle(token);
if (tokenDuplicate != IntPtr.Zero)
CloseHandle(tokenDuplicate);
return false;
}
private void undoImpersonation()

...{
impersonationContext.Undo();
}

}