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
/// <summary>
/// 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。
/// </summary>
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;
public partial class TextBoxWithDataPick : UserControl
{
public TextBoxWithDataPick()
{
InitializeComponent();
}
/// <summary>文本</summary>
public string text
{ get{ return textBox1.Text; }
set{ textBox1.Text = value;}
}
/// <summary>可供用户选择的数据集</summary>
public DataTable dataSource = null;
/// <summary>在dataSource中的列名</summary>
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();
}
}
}