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);
                }   
            }
        }