experiment

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

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

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

            textBox1.BackColor = Color.Yellow;

            if (Environment.OSVersion.Version.Major != 6.01)
            { textBox1.BackColor = Color.White; }

                string input = textBox1.Text;
        }

        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            comboBox1.BackColor = Color.Yellow;

            if (Environment.OSVersion.Version.Major != 6.01)
            { comboBox1.BackColor = Color.White; }


            if (comboBox1.SelectedIndex == 0)
            {
                string input = textBox1.Text;
                Process.Start("www.google.bg/#newwindow=1&q=" + textBox1.Text);
            }

            if (comboBox1.SelectedIndex == 1)
            {
                string input = textBox1.Text;
                Process.Start("www.google.bg/#newwindow=1&q=" + textBox1.Text +" site:"+ comboBox1.Text);
            }

            if (comboBox1.SelectedIndex == 2)
            {
                string input = textBox1.Text;
                Process.Start("www.google.bg/#newwindow=1&q=" + textBox1.Text + " site:" + comboBox1.Text);
            }

            if (comboBox1.SelectedIndex == 3)
            {
                string input = textBox1.Text;
                Process.Start("www.google.bg/#newwindow=1&q=" + textBox1.Text + " site:" + comboBox1.Text);
            }

            if (comboBox1.SelectedIndex == 4)
            {
                string input = textBox1.Text;
                Process.Start("www.google.bg/#newwindow=1&q=" + textBox1.Text + " site:" + comboBox1.Text);
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void label1_Click(object sender, EventArgs e)
        {
            label1.ForeColor = Color.Yellow;
        }

        private void label2_Click(object sender, EventArgs e)
        {
            label2.ForeColor = Color.Yellow;
        }

        private void label3_Click(object sender, EventArgs e)
        {
            label3.ForeColor = Color.Yellow;
        }
    }
}