DP44/Common/DTS.Common.Utilities/CheckComboBox.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Windows.Forms.VisualStyles;

namespace DTS.Common.Utilities
{

    /// <summary>
    /// This class wraps the list items in the combo box
    /// </summary>
    public class CheckComboBoxItem
    {
        /// <summary>
        /// C'tor - creates a CheckComboBoxItem
        /// </summary>
        /// <param name="text">Label of the check box in the drop down list</param>
        /// <param name="initialCheckState">Initial value for the check box (true=checked)</param>
        public CheckComboBoxItem(string text, bool initialCheckState)
        {
            CheckState = initialCheckState;
            Text = text;
        }

        /// <summary>
        /// Get or set the check value (true=checked)
        /// </summary>
        public bool CheckState { get; set; } = false;

        /// <summary>
        /// Gets the label of the check box
        /// </summary>
        public string Text { get; set; } = "";

        /// <summary>
        /// User defined data
        /// </summary>
        public object Tag { get; set; } = null;

        /// <summary>
        /// This is used to keep the edit control portion of the combo box consistent
        /// </summary>
        /// <returns></returns>
        public override string ToString()
        {
            return "Select Options";
        }

    }

    /// <summary>
    /// Inherits from ComboBox and handles DrawItem and SelectedIndexChanged events to create an
    /// owner drawn combo box drop-down.  The contents of the dropdown are rendered using the
    /// CheckBoxRenderer class.
    /// </summary>
    public partial class CheckComboBox : ComboBox
    {
        /// <summary>
        /// C'tor
        /// </summary>
        public CheckComboBox()
        {
            DrawMode = DrawMode.OwnerDrawFixed;
            DrawItem += CheckComboBox_DrawItem;
            SelectedIndexChanged += CheckComboBox_SelectedIndexChanged;
            SelectedText = "Select Options";
        }

        /// <summary>
        /// Invoked when the selected index is changed on the dropdown.  This sets the check state
        /// of the CheckComboBoxItem and fires the public event CheckStateChanged using the 
        /// CheckComboBoxItem as the event sender.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void CheckComboBox_SelectedIndexChanged(object sender, EventArgs e)
        {
            var item = (CheckComboBoxItem)SelectedItem;
            if (item == null)
                return;
            item.CheckState = !item.CheckState;
            if (CheckStateChanged != null)
                CheckStateChanged(item, e);
        }

        /// <summary>
        /// Invoked when the ComboBox has to render the drop-down items.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void CheckComboBox_DrawItem(object sender, DrawItemEventArgs e)
        {
            // make sure the index is valid (sanity check)
            if (e.Index == -1)
            {
                return;
            }

            // test the item to see if its a CheckComboBoxItem
            if (!(Items[e.Index] is CheckComboBoxItem))
            {
                // it's not, so just render it as a default string
                e.Graphics.DrawString(
                    Items[e.Index].ToString(),
                    Font,
                    Brushes.Black,
                    new Point(e.Bounds.X, e.Bounds.Y));
                return;
            }

            // get the CheckComboBoxItem from the collection
            var box = (CheckComboBoxItem)Items[e.Index];

            // render it
            CheckBoxRenderer.RenderMatchingApplicationState = true;
            CheckBoxRenderer.DrawCheckBox(
                e.Graphics,
                new Point(e.Bounds.X, e.Bounds.Y),
                e.Bounds,
                box.Text,
                Font,
                (e.State & DrawItemState.Focus) == 0,
                box.CheckState ? CheckBoxState.CheckedNormal : CheckBoxState.UncheckedNormal);
        }

        /// <summary>
        /// Fired when the user clicks a check box item in the drop-down list
        /// </summary>
        public event EventHandler CheckStateChanged;

    }
}