How to Add Items in ComboBox in C#? - GeeksforGeeks

27 Jun, 2019
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. You are allowed to a list or collection of elements in your ComboBox by using Items Property. You can set this property using two different methods:
1. Design-Time: It is the easiest method to add the items in the 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 add the collection of elements in the ComboBox.Output:
Output:
2. Run-Time: It is a little bit trickier than the above method. In this method, you can add the list of elements in the ComboBox programmatically with the help of given syntax:
public System.Windows.Forms.ComboBox.ObjectCollection Items { get; }
Here, the ComboBox.ObjectCollection indicates the elements present in the ComboBox. Following steps are used to add the elements in the 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();

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

Step 2: After creating ComboBox, add the elements in the ComboBox.// Adding elements in the combobox
mybox.Items.Add(230);
mybox.Items.Add(231);
mybox.Items.Add(232);
mybox.Items.Add(233);
mybox.Items.Add(234);;

// Adding elements in the combobox
mybox.Items.Add(230);
mybox.Items.Add(231);
mybox.Items.Add(232);
mybox.Items.Add(233);
mybox.Items.Add(234);;

Step 3: And last add this combobox control to form using Add() method.// Add this ComboBox to form
this.Controls.Add(mybox);
Example: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 WindowsFormsApp11 {  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(222, 80);        l.Size = new Size(99, 18);        l.Text = "Select Your id";          // 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.Name = "My_Cobo_Box";        mybox.Items.Add(230);        mybox.Items.Add(231);        mybox.Items.Add(232);        mybox.Items.Add(233);        mybox.Items.Add(234);          // Adding this ComboBox to the form        this.Controls.Add(mybox);    }}}Output:
// Add this ComboBox to form
this.Controls.Add(mybox);

Example:
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 WindowsFormsApp11 {  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(222, 80);        l.Size = new Size(99, 18);        l.Text = "Select Your id";          // 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.Name = "My_Cobo_Box";        mybox.Items.Add(230);        mybox.Items.Add(231);        mybox.Items.Add(232);        mybox.Items.Add(233);        mybox.Items.Add(234);          // Adding this ComboBox to the form        this.Controls.Add(mybox);    }}}
Output:
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