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ComboBox in C# - GeeksforGeeks

Last Updated : 12 Jul, 2025

In Windows Forms, the ComboBox control combines the features of a TextBox and a ListBox. It displays one item at a time, with additional items accessible through a drop-down menu. The ComboBox class is part of the System.Windows.Forms namespace.

There are mainly two ways to create a ComboBox in Windows forms which are mentioned below.

• Drag and drop (Design-Time)
• Custom ComboBox (Run-Time)

This is the easiest way to create a ComboBox in Windows Forms using Visual Studio we just have to open the toolbox and drag and drop the button on the form in the designer and further we can change the appearance of the ComboBox using the properties. Follow these steps to create a ComboBox.

Step 1: Now locate the project with the name here we are using the default name which is Form1 and it will open a form in the editor that we can further modify.

In the image, we have two files that are open one Design and there is Form1.cs these two play a major role. We use the Form1.cs file for custom logic.

Step 2: Now open a Toolbox go to the view > Toolbox or ctrl + alt + x.

Step 3. Now open the common controls and drag and drop the ComboBox on the form where we want to it be placed.

Step 4. Now open the properties of the button press right-click on the ComboBox and it will open the properties solution explorer now we can change the appearance and the behaviour of the button.

Step 5: In the properties, we can make different types of changes we can add the items in the list which is available at the left-most bottom in the properties as shown in the image

It will open the new box (String Collection Editor ) here we can add a different list and each line is a separate list as shown in the image after adding the list click on the OK button.

Output:

In this method, we are going to modify the Form1.cs file and add custom code modification in C# with the help of the ComboBox class. The following steps show how to create a ComboBox dynamically:

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

// Creating ComboBox

ComboBox MyComboBox = 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 to 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);

Step 4: Now double-click on the form in Design and it will open the Form1.cs file where code is written in C#. Here the program file is Form 1.cs Now write this code in Form1.cs file

Form1.cs file:

namespace WinFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // Creating and setting the properties of the label
            Label l = new Label
            {
                Location = new Point(122, 80),
                AutoSize = true,
                Text = "Select Programming Language"
            };

            // Creating and setting the properties of the ComboBox
            ComboBox mybox = new ComboBox
            {
                Location = new Point(327, 77),
                Size = new Size(216, 26)
            };

            // Adding items to the ComboBox
            mybox.Items.AddRange(new object[] { "C#", "Java", "Scala", "C", "C++" });

            // Adding controls to the form
            this.Controls.Add(l);
            this.Controls.Add(mybox);

        }
    }
}

Output:

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