Example with ComboBox:-

Add a new Form i.e.,ForComboBox1 to the Windows Application WABasics

Create three labels,two textboxes and six buttons ,one listBox& set the following properties to them

label1:      Text      : Enter AnyItem      Name   : lblItem label2:      Text     : Enter Any index      Name   : lblIndex label3:      Text     : Select Any Item      Name   : lblSelectItem

textbox1:      Name   : txtItem textbox2:      Name   : txtIndex comboBox1:      Name         : cmbItems

button1:      Name   : btnAdd      Text     : Add button2:      Name   : btnInsertSubtract      Text     : Insert button3:      Name   : btnRemove      Text     : Remove button4:      Name   : btnRemoveAt      Text     : RemoveAt Button5:      Name   : btnClear      Text     : Clear Button6:      Name   : btnClose      Text     : Close

Design :-

Generate the EventHandlers  for btnAdd ,btnInsert,btnRemove,btnRemoveAt,btnClear,btnClose buttons clickEvents

Generate the Event Handler for cmbItems Default Event i.e.,SelectedIndexChanged

& write the following code in Source[FormComboBox1.cs] 

using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace WABasics {     public partial class FormComboBox1 : Form     {         public FormComboBox1()         {             InitializeComponent();         }         private void btnAdd_Click(object sender, EventArgs e)         {             cmbSample.Items.Add(txtItem.Text);         }         private void btnInsert_Click(object sender, EventArgs e)         {             cmbSample.Items.Insert(Convert.ToInt32(txtIndex.Text),txtItem.Text);         }         private void btnRemove_Click(object sender, EventArgs e)         {             cmbSample.Items.Remove(txtItem.Text);         }         private void btnRemoveAt_Click(object sender, EventArgs e)         {             cmbSample.Items.RemoveAt(Convert.ToInt32(txtIndex.Text));         }         private void btnClear_Click(object sender, EventArgs e)         {             cmbSample.Items.Clear();         }         private void btnClose_Click(object sender, EventArgs e)         {             this.Close();         }         private void cmbSample_SelectedIndexChanged(object sender, EventArgs e)         {             txtIndex.Text = cmbSample.SelectedIndex.ToString();             txtItem.Text = cmbSample.SelectedItem.ToString();         }            } }

Result :-

Add

Insert