C# Winform 工控机 多选下拉框 MultiComboBox

作为寄几第一个写的较复杂的控件，把整个规程完整的写下来。整体思路是用现成的ComboBox和CheckedListBox组合实现功能

平台：VS2022，Framework4.8

一、效果

 二、编写代码

1.新建“Windows窗体应用（.NET Framework），采用默认设置

2.添加新类，命名为MultiComboBox，在其中添加如下代码

1.  
   using System;
2.  
   using System.Collections.Generic;
3.  
   using System.Drawing;
4.  
   using System.Windows.Forms;
5.  
    
6.  
   namespace MultiComboBox
7.  
   {
8.  
   internal class MultiComboBox : UserControl
9.  
   {
10.  
    private ComboBox comboBox = new ComboBox();
11.  
    public CheckedListBox CheckedListBox { get; set; } //为选项赋值的接口
12.  
    public List<string> SelectedItems1 { get; set; } //传递已选择项目的接口
13.  
     
14.  
    public MultiComboBox()
15.  
    {
16.  
    this.VerticalScroll.Enabled = true;
17.  
    this.AutoSize = true;
18.  
    CheckedListBox=new CheckedListBox();
19.  
    CheckedListBox.CheckOnClick = true;
20.  
    CheckedListBox.Visible = false;
21.  
    comboBox=new ComboBox();
22.  
    comboBox.Width = 150;
23.  
    comboBox.DrawMode = DrawMode.OwnerDrawFixed;
24.  
    comboBox.IntegralHeight = false;
25.  
    comboBox.DroppedDown = false;
26.  
    comboBox.DropDownHeight = 1;
27.  
    comboBox.DropDownStyle = ComboBoxStyle.DropDown;
28.  
    comboBox.AutoCompleteSource = AutoCompleteSource.ListItems;
29.  
    CheckedListBox.MouseUp = MouseUp1;
30.  
    CheckedListBox.MouseLeave = MouseLeave1;
31.  
    comboBox.MouseDown = MouseDown1;
32.  
    comboBox.DropDown = MouseLeave2;
33.  
    this.Controls.Add(comboBox); //添加控件
34.  
    }
35.  
    //
36.  
    #region 订阅方法模块
37.  
    //
38.  
    private void MouseLeave1(object sender, EventArgs e) //鼠标离开CheckedListBox，隐藏CheckedListBox
39.  
    {
40.  
    CheckedListBox.Hide();
41.  
    }
42.  
    private void MouseLeave2(object sender, EventArgs e) //ComboBox下拉时，显示下拉框
43.  
    {
44.  
    // 显示下拉框
45.  
    CheckedListBox.Width = comboBox.Width;
46.  
    CheckedListBox.Size = new Size(comboBox.DropDownWidth, CheckedListBox.Items.Count*18);
47.  
    CheckedListBox.Location = new Point(comboBox.Left, comboBox.Height);
48.  
    Controls.Add(CheckedListBox);
49.  
    CheckedListBox.Visible = true;
50.  
    }
51.  
    private void MouseUp1(object sender, EventArgs e) //在CheckedListBox中选择后，在ComboBox中显示相应项目
52.  
    {
53.  
    var list = new List<string>();
54.  
    foreach (var v in CheckedListBox.CheckedItems) //将选择的项目加入list
55.  
    {
56.  
    list.Add(v.ToString());
57.  
    }
58.  
    comboBox.Text = String.Join(",", list);
59.  
    SelectedItems1 = list; //把选项赋给传递接口
60.  
    }
61.  
    private void MouseDown1(object sender, EventArgs e) //在ComboBox的下拉三角按下鼠标时，不显示ComboBox的下拉框，显示CheckedListBox当作其下拉框
62.  
    {
63.  
    comboBox.DroppedDown = false;
64.  
    }
65.  
    #endregion
66.  
    //
67.  
    private void InitializeComponent()
68.  
    {
69.  
    this.SuspendLayout();
70.  
    //
71.  
    // MultiComboBox
72.  
    //
73.  
    this.Name = "MultiComboBox";
74.  
    this.Size = new System.Drawing.Size(414, 84);
75.  
    this.ResumeLayout(false);
76.  
    }
77.  
    }
78.  
    }

3.重新生成解决方案后，在”Form1.cs[设计]“中拖入MultiComboBox、Button

 在Form1.cs中添加如下代码

1.  
   using System.Data;
2.  
   using System.Drawing;
3.  
   using System.Linq;
4.  
   using System.Text;
5.  
   using System.Threading.Tasks;
6.  
   using System.Windows.Forms;
7.  
    
8.  
   namespace MultiComboBox
9.  
   {
10.  
    public partial class Form1 : Form
11.  
    {
12.  
    public Form1()
13.  
    {
14.  
    InitializeComponent();
15.  
    }
16.  
     
17.  
    private void Form1_Load(object sender, EventArgs e)
18.  
    {
19.  
    //为下拉菜单添加选项
20.  
    multiComboBox1.CheckedListBox.Items.Add("1");
21.  
    multiComboBox1.CheckedListBox.Items.Add("2");
22.  
    multiComboBox1.CheckedListBox.Items.Add("3");
23.  
    multiComboBox1.CheckedListBox.Items.Add("4");
24.  
    multiComboBox1.CheckedListBox.Items.Add("5");
25.  
    }
26.  
     
27.  
    private void button1_Click(object sender, EventArgs e) //单击button时，通过MultiComboBox的接口显示已选项目
28.  
    {
29.  
    var a = multiComboBox1.SelectedItems1;
30.  
    string b = string.Join(",", a);
31.  
    MessageBox.Show(b);
32.  
    }
33.  
    }
34.  
    }

运行即可

注：

Form1.Designer.cs中自动添加的代码，有时候添加

this.multiComboBox1 = new MultiComboBox.MultiComboBox();

会报错，改为

this.multiComboBox1 = new MultiComboBox();

即可

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