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ComboBox in C#

  • Last Updated : 30 Jun, 2019
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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:




    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:

Important Properties of the ComboBox

PropertyDescription
BackColorThis property is used to set the background color for the ComboBox control.
DropDownHeightThis property is used to set the height in pixels of the drop-down portion of the ComboBox control.
DropDownStyleThis property is used to set a value specifying the style of the ComboBox control.
DropDownWidthThis property is used to set the width of the of the drop-down portion of a ComboBox control.
FontThis property is used to set the font of the text displayed by the ComboBox control.
ForeColorThis property is used to set the foreground color of the ComboBox control.
HeightThis property is used to set the height of the ComboBox control.
ItemsThis property is used to get an object representing the collection of the items contained in this ComboBox control.
MaxDropDownItemsThis property is used to set the maximum number of items to be shown in the drop-down portion of the ComboBox control.
MaxLengthThis property is used to set the number of characters a user can type into the ComboBox control.
NameThis property is used to set the name of the ComboBox control.
SelectedItemThis property is used to set currently selected item in the ComboBox.
SizeThis property is used to set the height and width of the ComboBox control.
SortedThis property is used to set a value indicating whether the items in the combo box are sorted.
TextThis property is used to set the text associated with this ComboBox control.
VisibleThis property is used to set a value indicating whether the control and all its child controls are displayed.

Important Events

EventDescription
ClickThis event occur when the ComboBox control is clicked.
DragDropThis event occur when a drag-and-drop operation is completed.
DropDownThis event occur when the drop-down portion of a ComboBox is shown.
DropDownClosedThis event occur when the drop-down portion of the ComboBox is no longer visible.
DropDownStyleChangedThis event occur when the DropDownStyle property has changed.
LeaveThis event occur when the input focus leaves the ComboBox control.
MouseClickThis event occur when the ComboBox control is clicked by the mouse.
MouseDoubleClickThis event occur when the ComboBox control is double clicked by the mouse.
MouseDownThis event occur when the mouse pointer is over the ComboBox control and a mouse button is pressed.
MouseEnterThis event occur when the mouse pointer enters the ComboBox control.
MouseHoverThis event occur when the mouse pointer rests on the ComboBox control.
SelectedIndexChangedThis event occur when the SelectedIndex property has changed.



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