此程序可以实现系统拨号找到系统的拨号设置，然后再拨号成功后，显示拨号状态，非原创，用C#移植了一下，原文参见CodeProject中关于Web 实现拨号的文章。

下面是拨号需要用到的文件，一个RAS自定义类，添加到工程文件中就可用，C#的

////////////////////

using System;
using System.Runtime.InteropServices;
using System.Text;

namespace Dialup.RAS
{
    public enum RasFieldSizeConstants
    {
        RAS_MaxDeviceType = 16,
        RAS_MaxPhoneNumber = 128,
        RAS_MaxIpAddress = 15,
        RAS_MaxIpxAddress = 21,
#if WINVER4
  RAS_MaxEntryName      =256,
  RAS_MaxDeviceName     =128,
  RAS_MaxCallbackNumber =RAS_MaxPhoneNumber,
#else
        RAS_MaxEntryName = 20,
        RAS_MaxDeviceName = 32,
        RAS_MaxCallbackNumber = 48,
#endif

        RAS_MaxAreaCode = 10,
        RAS_MaxPadType = 32,
        RAS_MaxX25Address = 200,
        RAS_MaxFacilities = 200,
        RAS_MaxUserData = 200,
        RAS_MaxReplyMessage = 1024,
        RAS_MaxDnsSuffix = 256,
        UNLEN = 256,
        PWLEN = 256,
        DNLEN = 15
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    public struct GUID
    {
        public uint Data1;
        public ushort Data2;
        public ushort Data3;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 8)]
        public byte[] Data4;
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    public struct RASCONN
    {
        public int dwSize;
        public IntPtr hrasconn;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = (int)RasFieldSizeConstants.RAS_MaxEntryName + 1)]
        public string szEntryName;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = (int)RasFieldSizeConstants.RAS_MaxDeviceType + 1)]
        public string szDeviceType;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = (int)RasFieldSizeConstants.RAS_MaxDeviceName + 1)]
        public string szDeviceName;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]//MAX_PAPTH=260
        public string szPhonebook;
        public int dwSubEntry;
        public GUID guidEntry;
#if (WINVER501)
   int     dwFlags;
   public LUID      luid;
#endif
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    public struct LUID
    {
        int LowPart;
        int HighPart;
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    public struct RasEntryName
    {
        public int dwSize;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = (int)RasFieldSizeConstants.RAS_MaxEntryName + 1)]
        public string szEntryName;
#if WINVER5
  public int dwFlags;
  [MarshalAs(UnmanagedType.ByValTStr,SizeConst=260+1)]
  public string szPhonebookPath;
#endif
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    public class RasStats
    {
        public int dwSize = Marshal.SizeOf(typeof(RasStats));
        public int dwBytesXmited;
        public int dwBytesRcved;
        public int dwFramesXmited;
        public int dwFramesRcved;
        public int dwCrcErr;
        public int dwTimeoutErr;
        public int dwAlignmentErr;
        public int dwHardwareOverrunErr;
        public int dwFramingErr;
        public int dwBufferOverrunErr;
        public int dwCompressionRatioIn;
        public int dwCompressionRatioOut;
        public int dwBps;
        public int dwConnectDuration;
    }

    public class RAS
    {

        [DllImport("Rasapi32.dll", EntryPoint = "RasEnumConnectionsA",
             SetLastError = true)]

        public static extern int RasEnumConnections
            (
                ref RASCONN lprasconn, // buffer to receive connections data
                ref int lpcb, // size in bytes of buffer
                ref int lpcConnections // number of connections written to buffer
            );

        [DllImport("rasapi32.dll", CharSet = CharSet.Auto)]
        public static extern uint RasGetConnectionStatistics(
            IntPtr hRasConn,       // handle to the connection
            [In, Out]RasStats lpStatistics  // buffer to receive statistics
            );
        [DllImport("rasapi32.dll", CharSet = CharSet.Auto)]
        public extern static uint RasHangUp(
            IntPtr hrasconn  // handle to the RAS connection to hang up
            );

        [DllImport("rasapi32.dll", CharSet = CharSet.Auto)]
        public extern static uint RasEnumEntries(
            string reserved,              // reserved, must be NULL
            string lpszPhonebook,         // pointer to full path and
            //  file name of phone-book file
            [In, Out]RasEntryName[] lprasentryname, // buffer to receive
            //  phone-book entries
            ref int lpcb,                  // size in bytes of buffer
            out int lpcEntries             // number of entries written
            //  to buffer
            );

        [DllImport("wininet.dll", CharSet = CharSet.Auto)]
        public extern static int InternetDial(
            IntPtr hwnd,
            [In]string lpszConnectoid,
            uint dwFlags,
            ref int lpdwConnection,
            uint dwReserved
            );

        public RAS()
        {

        }
    }

    public class RASDisplay
    {
        private string m_duration;
        private string m_ConnectionName;
        private string[] m_ConnectionNames;
        private double m_TX;
        private double m_RX;
        private bool m_connected;
        private IntPtr m_ConnectedRasHandle;

        public RASDisplay()
        {
            m_connected = true;

            RAS lpras = new RAS();
            RASCONN lprasConn = new RASCONN();

            lprasConn.dwSize = Marshal.SizeOf(typeof(RASCONN));
            lprasConn.hrasconn = IntPtr.Zero;

            int lpcb = 0;
            int lpcConnections = 0;
            int nRet = 0;
            lpcb = Marshal.SizeOf(typeof(RASCONN));

            nRet = RAS.RasEnumConnections(ref lprasConn, ref lpcb, ref
    lpcConnections);

            if (nRet != 0)
            {
                m_connected = false;
                return;
            }

            if (lpcConnections > 0)
            {
                RasStats stats = new RasStats();

                m_ConnectedRasHandle = lprasConn.hrasconn;
                RAS.RasGetConnectionStatistics(lprasConn.hrasconn, stats);

                m_ConnectionName = lprasConn.szEntryName;

                int Hours = 0;
                int Minutes = 0;
                int Seconds = 0;

                Hours = ((stats.dwConnectDuration / 1000) / 3600);
                Minutes = ((stats.dwConnectDuration / 1000) / 60) - (Hours * 60);
                Seconds = ((stats.dwConnectDuration / 1000)) - (Minutes * 60) - (Hours * 3600);

                m_duration = Hours + " hours " + Minutes + " minutes " + Seconds + " secs";
                m_TX = stats.dwBytesXmited;
                m_RX = stats.dwBytesRcved;
            }
            else
            {
                m_connected = false;
            }

            int lpNames = 1;
            int entryNameSize = 0;
            int lpSize = 0;
            RasEntryName[] names = null;

            entryNameSize = Marshal.SizeOf(typeof(RasEntryName));
            lpSize = lpNames * entryNameSize;

            names = new RasEntryName[lpNames];
            names[0].dwSize = entryNameSize;

            uint retval = RAS.RasEnumEntries(null, null, names, ref lpSize, out lpNames);

            //if we have more than one connection, we need to do it again
            if (lpNames > 1)
            {
                names = new RasEntryName[lpNames];
                for (int i = 0; i < names.Length; i++)
                {
                    names[i].dwSize = entryNameSize;
                }

                retval = RAS.RasEnumEntries(null, null, names, ref lpSize, out lpNames);

            }
            m_ConnectionNames = new string[names.Length];

            if (lpNames > 0)
            {
                for (int i = 0; i < names.Length; i++)
                {
                    m_ConnectionNames[i] = names[i].szEntryName;
                }
            }
        }

        public string Duration
        {
            get
            {
                return m_connected ? m_duration : "";
            }
        }

        public string[] Connections
        {
            get
            {
                return m_ConnectionNames;
            }
        }

        public double BytesTransmitted
        {
            get
            {
                return m_connected ? m_TX : 0;
            }
        }
        public double BytesReceived
        {
            get
            {
                return m_connected ? m_RX : 0;
            }
        }
        public string ConnectionName
        {
            get
            {
                return m_connected ? m_ConnectionName : "";
            }
        }
        public bool IsConnected
        {
            get
            {
                return m_connected;
            }
        }

        public int Connect(string Connection)
        {
            int temp = 0;
            uint INTERNET_AUTO_DIAL_UNATTENDED = 2;
            int retVal = RAS.InternetDial(IntPtr.Zero, Connection, INTERNET_AUTO_DIAL_UNATTENDED, ref temp, 0);
            return retVal;
        }
        public void Disconnect()
        {
            RAS.RasHangUp(m_ConnectedRasHandle);
        }
    }
}

下面是引用这个代码的实例，加入一个comboBox来显示拨号的设置，用两个button来控制连接状态，用八个label来显示连接后的状态信息，希望对大家有用处。原Web程序参见CodeProject中的文章

//////////////////////////////////////////////////////////////////////

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using Dialup.RAS;

namespace Dialup
{
    public partial class frmMain : Form
    {
        public frmMain()
        {
            InitializeComponent();
           
            BindData();           
        }

        private void BindData()
        {
            try
            {
                RASDisplay display = new RASDisplay();

                lblName.Text = display.ConnectionName;
                lblDuration.Text = display.Duration;
                lblReceived.Text = display.BytesReceived.ToString();
                lblTransmitted.Text = display.BytesTransmitted.ToString();

                if (!display.IsConnected)
                {
                    tblCurrentConnection.Visible = false;
                    cboAllConnections.Visible = true;
                    timer1.Stop();
                }
                else
                {
                    tblCurrentConnection.Visible = true;
                    cboAllConnections.Visible = false;
                    timer1.Start();
                }

                cboAllConnections.DataSource = display.Connections;
            }
            catch (Exception e)
            {
                MessageBox.Show(e.Message);
            }
        }

        protected void btnConnect_Click(object sender, EventArgs e)
        {
            RASDisplay rasDisplay = new RASDisplay();

            int ErrorVal = rasDisplay.Connect(cboAllConnections.Text);

            if (ErrorVal != 0)
                MessageBox.Show(ErrorVal.ToString());
            else
                timer1.Start();
        }
        protected void btnDisConnect_Click(object sender, EventArgs e)
        {
            RASDisplay rasDisplay = new RASDisplay();
            rasDisplay.Disconnect();
            BindData();           
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            BindData();
        }
    }
}

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/bukater/archive/2007/04/01/1548545.aspx