How to Add Items in C# ComboBox

1. Create a ComboBox in C#
2. Add an Item in ComboBox in C#

In this guide, we’ll see how to add items to ComboBox in C#.

Create a ComboBox in C#

Before adding an item to a ComboBox, we must understand how a ComboBox is created. We have two methods for creating a ComboBox.

We can use windows forms or the ComboBox class at run time to create it in C#.

Use ToolBox to Create a ComboBox in C#

Using the toolbox, we can create a ComboBox control at design time. We can drag ComboBox from the toolbox, and it will be created.

We create as we want using its properties. By right-clicking on the newly created ComboBox, we can add items to it.

Use ComboBox Class to Create a ComboBox in C#

Creating a ComboBox at run-time is a little more tricky and more complex than by toolbox(Design-time). In the following example, we’ll use the ComboBox class to create a ComboBox and add an item to it.

Add an Item in ComboBox in C#

As mentioned above, adding an item in ComboBox can be a little more complex than using a toolbox. We have to use the Add() method to add an item, and this method is from the ObjectCollection class.

We use a ComboBox() constructor to create a ComboBox so that we can add our items to it. We can also set its properties to our desires.

After creating a ComboBox, items can now be added. At last, we have to use the Add() method to add the ComboBox control to the form.

Code:

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 WindowsFormsApp1 {
  public partial class Form1 : Form {
    public Form1() {
      InitializeComponent();
    }
    private void Form1_Load(object sender, EventArgs e) {
      ComboBox comboBox1 = new ComboBox();  // creating a combobox
      comboBox1.Location = new Point(327, 77);
      comboBox1.Size = new Size(216, 26);
      comboBox1.Name = "MY COMBOBOX";

      comboBox1.Items.Add(389);  // adding items in combobox
      comboBox1.Items.Add(390);
      comboBox1.Items.Add(391);

      this.Controls.Add(comboBox1);  // Adding this ComboBox to the form
    }
  }
}

Output: