自由手記

using System;
using System.Net;
using System.Text;
using System.Windows.Forms;

namespace GetIPorDNS
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btnGetHostName_Click(object sender, EventArgs e)
        {
            try
            {
                txtDNS.Text = Dns.GetHostEntry("").HostName;
            }
            catch (Exception ex)
            {
                txtDNS.Text = ex.Message;
            }
        }

        private void btnIP2DNS_Click(object sender, EventArgs e)
        {
            try
            {
                txtHostName.Text = Dns.GetHostEntry(txtIP.Text.Trim()).HostName;
            }
            catch (Exception ex)
            {
                txtHostName.Text = ex.Message;
            }
        }

        private void txtDNS_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
            {
                btnDNS2IP.PerformClick();
            }
        }

        private void txtIP_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
            {
                btnIP2DNS.PerformClick();
            }
        }

        private void btnGetIP_Click(object sender, EventArgs e)
        {
            SetltbIP("");
        }

        private void btnDNS2IP_Click(object sender, EventArgs e)
        {
            SetltbIP(txtDNS.Text.Trim());
        }

        private void SetltbIP(string HostName)
        {
            ltbIP.BeginUpdate();
            ltbIP.Items.Clear();
            try
            {
                IPHostEntry ip = Dns.GetHostEntry(HostName);
                foreach (IPAddress i in ip.AddressList)
                {
                    ltbIP.Items.Add(i.ToString());
                }
            }
            catch (Exception ex)
            {
                ltbIP.Items.Add(ex.Message);
            }
            finally
            {
                ltbIP.EndUpdate();
            }
        }

        private void mnuCopy_Click(object sender, EventArgs e)
        {
            if (ltbIP.Items.Count == 0) return;
            if (ltbIP.SelectedIndex < 0) ltbIP.SelectedIndex = 0;
            Clipboard.Clear();
            StringBuilder sb = new StringBuilder();
            foreach (string item in ltbIP.SelectedItems)
            {
                sb.AppendFormat("\r\n{0}", item);
            }
            if (sb.Length > 0)
            {
                sb.Remove(0, 2);
            }
            Clipboard.SetText(sb.ToString());
        }

        private void mnuAll_Click(object sender, EventArgs e)
        {
            if (ltbIP.Items.Count == 0) return;
            for (int i = 0; i < ltbIP.Items.Count; i++)
            {
                ltbIP.SetSelected(i, true);
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            ltbIP.BeginUpdate();
            ltbIP.Items.Clear();
            try
            {
                WebClient wc = new WebClient();
                wc.Proxy = WebProxy.GetDefaultProxy();
                wc.Proxy.Credentials = System.Net.CredentialCache.DefaultCredentials;
                ltbIP.Items.Add(wc.DownloadString("http://pchelplive.com/ip.php"));
            }
            catch (Exception ex)
            {
                ltbIP.Items.Add(ex.Message);
            }
            finally
            {
                ltbIP.EndUpdate();
            }
        }

        private void ltbIP_SelectedIndexChanged(object sender, EventArgs e)
        {

        }
    }
}

https://docs.google.com/file/d/0B61rwP6vdmF5TS1PRkRYejJ4RTQ/edit?usp=sharing