Getting href

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

using System.Net;
using System.IO;
using System.Text.RegularExpressions;

namespace SEO_Tools
{
    public partial class formMain : Form
    {

        public formMain()
        {
            InitializeComponent();
            CheckForIllegalCrossThreadCalls = false;

        }

        private void btnCrawl_Click(object sender, EventArgs e)
        {
            WebClient WebC = new WebClient();
            String content = "";
            if (rbURL.Checked)
            {
                if (tbUrl.Text == "")
                {
                    MessageBox.Show("Bitte gib eine URL an");
                    return;
                }
                if (!(tbUrl.Text.StartsWith("http://")))
                {
                    tbUrl.Text = "http://" + tbUrl.Text;
                }
                try
                {
                    content = WebC.DownloadString(new Uri(tbUrl.Text));
                }
                catch
                {
                    MessageBox.Show("Die Seite konnte nicht geladen werden!");
                }
            }
            else if (rbFile.Checked)
            {
                if (File.Exists(tbUrl.Text))
                {
                    try
                    {
                        content = File.ReadAllText(tbUrl.Text);
                    }
                    catch
                    {
                        MessageBox.Show("Datei konnte nicht geöffnet werden");
                    }
                }
                else
                {
                    MessageBox.Show("Datei existiert nicht");
                }
            }
            String[] words = Regex.Split(content, "href=");
            int i = 1;
            tbOut.Text = null;
            foreach (String word in words)
            {
                try
                {
                    String[] temp = Regex.Split(words[i], "\"");
                    tbOut.Text += temp[1] + Environment.NewLine;
                }
                catch
                {
                    btnExport.Enabled = true;
                    break;
                }

                i++;
            }

        }

        private void btnExport_Click(object sender, EventArgs e)
        {
            String content = tbOut.Text;
            SaveFileDialog sfd = new SaveFileDialog();
            sfd.ShowDialog();
            String file = sfd.FileName;
            file += ".txt";
            File.WriteAllText(file, tbOut.Text);
        }

        private void rbURL_CheckedChanged(object sender, EventArgs e)
        {
            if (rbURL.Checked)
            {
                rbFile.Checked = false;
            }
        }

        private void rbFile_CheckedChanged(object sender, EventArgs e)
        {
            if (rbFile.Checked)
            {
                rbURL.Checked = false;
            }
        }

        private void tbUrl_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar == '\r')
            {
                btnCrawl_Click((object)sender, (EventArgs)e);
            }
        }

        private void btnBrowse_Click(object sender, EventArgs e)
        {
            OpenFileDialog ofd = new OpenFileDialog();
            DialogResult result = new DialogResult();
            result = ofd.ShowDialog();
            if (!(result == DialogResult.Cancel || result == DialogResult.Abort))
            {
                if (ofd.CheckFileExists)
                {
                    rbFile.Checked = true;
                    tbUrl.Text = ofd.FileName;
                    btnCrawl_Click((object)sender, (EventArgs)e);
                }
            }
        }

        private void formMain_Load(object sender, EventArgs e)
        {

        }
    }
}