C# FORM 自定义控件:带弹出(下拉)菜单的TextBox

程序需要做一个带下拉菜单的文本框以方便用户输入,大概类似于下图中这种TextBox:

 

控件有一个数据源,用的DataTable格式,还有一个值columnName来表示用Table中的哪一列数据,控件将根据这一列的数据来进行下拉框提示.

界面只添加了一个文本框和一个ListBox,

组件生成器中的代码为:

        #region 组件设计器生成的代码
        /// 
 
        /// 设计器支持所需的方法 - 不要
        /// 使用代码编辑器修改此方法的内容。
        /// 
        private void InitializeComponent()
        {
            this.textBox1 = new System.Windows.Forms.TextBox();
            this.listBox1 = new System.Windows.Forms.ListBox();
            this.SuspendLayout();
            // 
            // textBox1
            // 
            this.textBox1.Dock = System.Windows.Forms.DockStyle.Top;
            this.textBox1.Location = new System.Drawing.Point(0, 0);
            this.textBox1.Name = "textBox1";
            this.textBox1.Size = new System.Drawing.Size(189, 21);
            this.textBox1.TabIndex = 0;
            this.textBox1.TextChanged += new System.EventHandler(this.textBox1_TextChanged);
            this.textBox1.KeyDown += new System.Windows.Forms.KeyEventHandler(this.textBox1_KeyDown);
            this.textBox1.Leave += new System.EventHandler(this.textBox1_Leave);
            // 
            // listBox1
            // 
            this.listBox1.Dock = System.Windows.Forms.DockStyle.Fill;
            this.listBox1.FormattingEnabled = true;
            this.listBox1.ItemHeight = 12;
            this.listBox1.Location = new System.Drawing.Point(0, 21);
            this.listBox1.Name = "listBox1";
            this.listBox1.Size = new System.Drawing.Size(189, 4);
            this.listBox1.TabIndex = 1;
            this.listBox1.Leave += new System.EventHandler(this.listBox1_Leave);
            this.listBox1.DoubleClick += new System.EventHandler(this.listBox1_DoubleClick);
            this.listBox1.KeyDown += new System.Windows.Forms.KeyEventHandler(this.listBox1_KeyDown);
            // 
            // TextBoxWithDataPick
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.Controls.Add(this.listBox1);
            this.Controls.Add(this.textBox1);
            this.Name = "TextBoxWithDataPick";
            this.Size = new System.Drawing.Size(189, 25);
            this.Load += new System.EventHandler(this.TextBoxWithDataPick_Load);
            this.ResumeLayout(false);
            this.PerformLayout();
        }
        #endregion
        private System.Windows.Forms.TextBox textBox1;
        private System.Windows.Forms.ListBox listBox1;

类代码为:

public partial class TextBoxWithDataPick : UserControl
    {
        public TextBoxWithDataPick()
        {
            InitializeComponent();
        }
        /// 
文本
  
        public string text
        { get{ return textBox1.Text; }
          set{ textBox1.Text = value;}
        }
        /// 
可供用户选择的数据集
   
        public DataTable dataSource = null;
        /// 
在dataSource中的列名
   
        public string columnName = "";
        private void TextBoxWithDataPick_Load(object sender, EventArgs e)
        {
            //控件载入时,将高度缩为与TextBox相等
            this.Height = textBox1.Height;
        }
        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            if (this.textBox1.Text == "" )
            {                
                this.Height = textBox1.Height;
                this.listBox1.Visible = false;
                this.SendToBack();
                return;
            }
            //这些情况下,不弹出选择框
            if (dataSource == null || columnName == "" || !dataSource.Columns.Contains(columnName))
                return;
            //根据用户当前输入的内容,筛选出与内容相符的记录,显示在列表框中
            this.listBox1.Items.Clear();
            for (int i = 0; i < dataSource.Rows.Count; i++)
            {
                if (dataSource.Rows[i][columnName].ToString().IndexOf(textBox1.Text) == 0)
                {
                    listBox1.Items.Add(dataSource.Rows[i][columnName].ToString());
                }
            }
            //如果记录数不为0,则将列表显示出来
            if (listBox1.Items.Count == 0)
            {
                this.Height = textBox1.Height;
                this.listBox1.Visible = false;
                this.SendToBack();
            }
            else
            {
                if (listBox1.Items.Count == 1)
                {
                    this.Height = textBox1.Height + 20 * listBox1.Items.Count;
                    this.listBox1.Visible = true;
                    this.BringToFront();
                }
                else if (listBox1.Items.Count<8)
                {
                    this.Height = textBox1.Height + 14 * listBox1.Items.Count;
                    this.listBox1.Visible = true;
                    this.BringToFront();
                }
                else
                {
                    this.Height = textBox1.Height + 108;
                    this.listBox1.Visible = true;
                    this.BringToFront();
                }
            }
        }
        //用户在焦点为listBox1时按下回车,将当前选中的内容提交到TextBox中,并隐藏ListBox
        private void listBox1_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyValue == (int)Keys.Enter)
            {
                this.textBox1.Text = listBox1.SelectedItem.ToString();
                this.Height = textBox1.Height;
                this.listBox1.Visible = false;
                this.SendToBack();
            }
        }
        //用户双击listBox1某项时,将当前选中的内容提交到TextBox中,并隐藏ListBox
        private void listBox1_DoubleClick(object sender, EventArgs e)
        {
            if (listBox1.SelectedItem != null)
            {
                this.textBox1.Text = listBox1.SelectedItem.ToString();
                this.Height = textBox1.Height;
                this.listBox1.Visible = false;
                this.SendToBack();
            }
        }
        //用户在TextBox中点击向下箭头时,将焦点交给ListBox,使用户能够选择其中的项
        private void textBox1_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyValue == (int)Keys.Down)
            {
                if (listBox1.Items.Count != 0)
                {
                    listBox1.Focus();
                    listBox1.SelectedIndex = 0;
                }
            }
        }
        //TextBox失去焦点时,隐藏ListBox
        private void textBox1_Leave(object sender, EventArgs e)
        {
            if (listBox1.Focused == false)
            {
                this.Height = textBox1.Height;
                this.listBox1.Visible = false;
                this.SendToBack();
            }
        }
        private void listBox1_Leave(object sender, EventArgs e)
        {
            if (textBox1.Focused == false)
            {
                this.Height = textBox1.Height;
                this.listBox1.Visible = false;
                this.SendToBack();
            }
        }
    }