C#里实现ComboBoxListBox

最新推荐文章于 2024-04-08 07:05:02 发布

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#c# #dropdown #dataset #null #object #string

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本文介绍了一种在ComboBox控件中实现ListBox功能的方法，包括多选功能，并提供了具体的源码实现细节。通过创建一个继承自ComboBox的类，利用ListBox进行数据绑定及事件处理，实现了类似于ListBox的交互体验。

ComboBoxListBox 在ComboBox控件里实现ListBox功能。如多选等。

ComboBoxListBox 源码：

public class ComboBoxListBox : ComboBox
    {
        private const int WM_LBUTTONDOWN = 0x201, WM_LBUTTONDBLCLK = 0x203;
        ToolStripControlHost listBoxHost;
        ToolStripDropDown dropDown;
        private ListBox Lstbox = new ListBox();
        public ComboBoxListBox()
        {
        }
        public ListBox Set_ComboBoxListBox
        {
            set
            {
                Lstbox = value;
                Lstbox.SelectedItems.Clear();
                Lstbox.BorderStyle = BorderStyle.None;
                Lstbox.SelectedIndexChanged += new EventHandler(Lstbox_SelectedIndexChanged);
                Lstbox.SelectionMode = SelectionMode.MultiSimple;
                listBoxHost = new ToolStripControlHost(Lstbox);
                listBoxHost.AutoSize = false;
                dropDown = new ToolStripDropDown();
                dropDown.Width = this.Width;
                dropDown.Items.Add(listBoxHost);
            }
            get
            {
                return Lstbox;
            }
        }

        void Lstbox_SelectedIndexChanged(object sender, EventArgs e)
        {
            string StrSel = "";
            for (int i = 0; i < Lstbox.SelectedItems.Count; i++)
            {
                StrSel += ((System.Data.DataRowView)Lstbox.SelectedItems[i])[Lstbox.ValueMember] + ",";
            }
            if (!string.IsNullOrEmpty(StrSel))
            {
                this.Text = StrSel.Substring(0, StrSel.Length - 1);
            }
            else
            {
                this.Text = "";
            }
        }

        public CheckedListBox CheckedListBox
        {
            get { return listBoxHost.Control as CheckedListBox; }
        }
        private void ShowDropDown()
        {
            if (dropDown != null)
            {
                listBoxHost.Size = new Size(DropDownWidth - 2, DropDownHeight);
                dropDown.Show(this, 0, this.Height);
            }
        }
        protected override void WndProc(ref Message m)
        {
            if (m.Msg == WM_LBUTTONDBLCLK || m.Msg == WM_LBUTTONDOWN)
            {
                ShowDropDown();
                return;
            }
            base.WndProc(ref m);
        }
        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                if (dropDown != null)
                {
                    dropDown.Dispose();
                    dropDown = null;
                }
            }
            base.Dispose(disposing);
        }
    }

用法：

            Ds 为 DataSet
            lst_Dept 为在窗口里放置的一个ListBox
            cbolst_Dept 为 ComboBoxListBox

            lst_Dept.DataSource = Ds.Tables[0].DefaultView;
            lst_Dept.DisplayMember = "DeptName";
            lst_Dept.ValueMember = "DeptID";

cbolst_Dept.Set_ComboBoxListBox = lst_Dept;