CheckBox

This control has 2 or 3 states. It provides a way for an option to be selected and deselected independently of other options.

Add a CheckBox control to your Windows Form in the designer view in Visual Studio. To use the CheckBox, add a Load event handler on the form.

CheckState

It is possible to set the CheckBox to allow three states. These include an indeterminate state as well as checked and unchecked.

using System;
using System.Windows.Forms;

namespace WindowsFormsApplication4
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            // Acquire the state of the CheckBox.
            CheckState state = checkBox1.CheckState;

            // Demonstrate how the CheckBox can be switched upon.
            switch (state)
            {
                case CheckState.Checked:
                case CheckState.Indeterminate:
                case CheckState.Unchecked:
                    {
                        MessageBox.Show(state.ToString());
                        break;
                    }
            }

            // Tell if the box is checked.
            MessageBox.Show(checkBox1.Checked.ToString());
        }
    }
}

CheckChanged

Typically, the CheckBox control is used alongside other controls. The CheckBox state is read when a user performs an action on another control, such as a button.

The CheckBox is useful control in Windows Forms. But it is not often a major focus of applications. It is instead a small, supporting control used with other controls.