星期三, 8月 03, 2022

[C#] CheckedListBox

根據官方文章 - CheckedListBox 的簡易筆記文
using System;
using System.Windows.Forms;

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

            Init();
        }

        private void Init()
        {
            btnAddFruit.Enabled = false;
            btnShow.Enabled = false;
            btnReset.Enabled = false;

            checkedListBox1.Items.Clear();
            listBox1.Items.Clear();

            // 預設新增資料
            string[] myFruit = { "Apples", "Oranges", "Tomato" };
            checkedListBox1.Items.AddRange(myFruit);
            checkedListBox1.Items.Add("Grape", true);

            // 預設為 false，先點選該項目後，才能勾選 CheckBox，開啟後就可以直接點選
            checkedListBox1.CheckOnClick = true;

            // 只支援 None 和 One，不支援 MultiSimple 和 MultiExtended
            //  使用 None 情況下就完全無法點選，One 為預設值
            checkedListBox1.SelectionMode = SelectionMode.One;
        }

        private void txtAddFruit_TextChanged(object sender, EventArgs e)
        {
            // 有輸入文字才能新增
            btnAddFruit.Enabled = string.IsNullOrWhiteSpace(txtAddFruit.Text) == false;
        }

        private void btnAddFruit_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrWhiteSpace(txtAddFruit.Text))
                return;

            if (checkedListBox1.CheckedItems.Contains(txtAddFruit.Text))
                return;

            // 新增後清空
            checkedListBox1.Items.Add(txtAddFruit.Text, CheckState.Checked);
            txtAddFruit.Text = string.Empty;
        }

        private void btnShow_Click(object sender, EventArgs e)
        {
            listBox1.Items.Clear();
            btnReset.Enabled = false;

            for (int i = 0; i < checkedListBox1.CheckedItems.Count; i++)
            {
                listBox1.Items.Add(checkedListBox1.CheckedItems[i]);
            }

            if (listBox1.Items.Count > 0)
                btnReset.Enabled = true;
        }

        private void checkedListBox1_ItemCheck(object sender, ItemCheckEventArgs e)
        {
            if (e.NewValue == CheckState.Unchecked)
            {
                // 點擊當下的 CheckBox = Checked 控件數量，判斷是否為最後一個 Checked
                if (checkedListBox1.CheckedItems.Count == 1)
                {
                    btnShow.Enabled = false;
                }
            }
            else
            {
                btnShow.Enabled = true;
            }
        }

        private void btnReset_Click(object sender, EventArgs e)
        {
            Init();
        }
    }
}

[C#] CheckedListBox


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