How to use ComboBox

Drag and drop ComboBox from toolbox on window Form.

Code:

using System;
using System.Text;
using System.Windows.Forms;
 
namespace WindowsFormsApplication1
{
     public partial class Form6 : Form
    {
         public Form6()
         {
            InitializeComponent();
         }
         private void Form6_Load(object sender, EventArgs e)
         {
            // Item is added in combobox
            comboBox1.Items.Add("C#");
            comboBox1.Items.Add("J#");
            comboBox1.Items.Add("VB");
            comboBox1.Items.Add("Java");
         }
 private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
         {
            // Selected value will show in Label
            label1.Text = "Selected Language is " +    comboBox1.SelectedItem.ToString();
         }
    }
}

Run the project

When you select the given option then SelectedIndexChanged event will fire and selected item will show in the Label.

AutoComplete ComboBox

Choose AutoCompleteSource property of ComboBox is ListItem and also set AutoCompleteMode to suggest, append, or SuggestAppend.

When you type any text in the ComboBox then it searches the related item and if related item is available then it suggest the related item.

ComboBox Properties:

AutoCompleteMode: Defines an option that controls how automatic completion works for the ComboBox.

AutoCompleteSource:  Defines a value specifying the source of complete strings used for automatic completion.

BackColor: BackColor of ComboBox is changed through BackColor property.

Example:

private void Form6_Load(object sender, EventArgs e)
{
      //change backcolor of comboBox
      comboBox1.BackColor = Color.CadetBlue;
}

Output