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;
   namespace ComboBox_Data_Add_Remove
   {
       public partial class Form1 : Form
       {   
           public Form1()
           {
               InitializeComponent();
           }
           private void button1_Click(object sender, EventArgs e)
           {
               comboBox1.Items.Add(textBox1.Text);
           }
           private void button2_Click(object sender, EventArgs e)
           {
               comboBox1.Items.Remove(textBox1.Text);
           }
           private void button4_Click(object sender, EventArgs e)
           {
               comboBox2.Items.Add(textBox2.Text);
           }
           private void button3_Click(object sender, EventArgs e)
           {
               comboBox2.Items.Remove(textBox2.Text);
           }
           private void button5_Click(object sender, EventArgs e)
           {
               comboBox2.Items.Add(comboBox1.Text);
               comboBox1.Items.Remove(comboBox1.Text);
           }
           private void button6_Click(object sender, EventArgs e)
           {
               comboBox1.Items.Add(comboBox2.Text);
               comboBox2.Items.Remove(comboBox2.Text);
           }
           private void button7_Click(object sender, EventArgs e)
           {
                for ( int k = 0 ; k < comboBox1.Items.Count ; k++)
                {
                    comboBox2.Items.Add(comboBox1.Items[k]);
                }
               comboBox1.Items.Clear();
           }
           private void button8_Click(object sender, EventArgs e)
           {
                for (int k = 0; k < comboBox2.Items.Count; k++)
                {
                    comboBox1.Items.Add(comboBox2.Items[k]);
                }
               comboBox2.Items.Clear();
           }
       }
   }