In Windows Forms, ComboBox provides two different features in a single control, it means ComboBox works as both TextBox and ListBox. In ComboBox, only one item is displayed at a time and the rest of the items are present in the drop-down menu. The ComboBox is a class in C# and defined under System.Windows.Forms Namespace. You can create ComboBox using the two different ways:

1. Design-Time: It is the easiest method to create a ComboBox control using the following steps:

• Step 1: Create a windows form as shown in the below image:
  Visual Studio -> File -> New -> Project -> WindowsFormApp
  
• Step 2: Drag the ComboBox control from the ToolBox and drop it on the windows form. You are allowed to place a ComboBox control anywhere on the windows form according to your need.
  
• Step 3: After drag and drop you will go to the properties of the ComboBox control to set the properties of the ComboBox according to your need.
  

  Output:
  

Run-Time: It is a little bit trickier than the above method. In this method, you can set create your own ComboBox control using the ComboBox class. Steps to create a dynamic ComboBox:

• Step 1: Create a combobox using the ComboBox() constructor is provided by the ComboBox class.

  // Creating combobox using ComboBox class
  ComboBox mybox = new ComboBox();
  

• Step 2: After creating ComboBox, set the properties of the ComboBox provided by the ComboBox class.

  // Set the location of the ComboBox 
  mybox.Location = new Point(327, 77);
  
  // Set the size of the ComboBox
  mybox.Size = new Size(216, 26);
  
  // Add items in the ComboBox
  mybox.Items.Add("C#");
  mybox.Items.Add("Java");
  mybox.Items.Add("Scala");
  mybox.Items.Add("C");
  mybox.Items.Add("C++");
  

• Step 3: And last add this ComboBox control to form using Add() method.

  // Add this ComboBox to the form
  this.Controls.Add(mybox);
  

  Example:

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  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 WindowsFormsApp18 {    public partial class Form1 : Form {        public Form1()     {         InitializeComponent();     }        private void Form1_Load(object sender, EventArgs e)     {         // Creating and setting the properties of label         Label l = new Label();         l.Location = new Point(122, 80);         l.AutoSize = true;         l.Text = "Select Programming Language";            // Adding this label to the form         this.Controls.Add(l);            // Creating and setting the properties of comboBox         ComboBox mybox = new ComboBox();         mybox.Location = new Point(327, 77);         mybox.Size = new Size(216, 26);         mybox.Items.Add("C#");         mybox.Items.Add("Java");         mybox.Items.Add("Scala");         mybox.Items.Add("C");         mybox.Items.Add("C++");            // Adding this ComboBox to the form         this.Controls.Add(mybox);     } } }

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  Output:

  

Important Properties of the ComboBox

Important Events