ComboBox in C# - GeeksforGeeks

30 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. 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:
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();

// 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++");

// 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: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);    }}}Output:
// Add this ComboBox to the 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 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);    }}}
Output:
C#
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