winform实现TextBox关键字智能提⽰
  有时候由于项⽬需求的需要，需要实现像百度那样输⼊关键字后有下拉框提⽰，在⽹上搜了下，⼀种是利⽤ComboBox和TextBox的AutoCompleteMode属性，个⼈感觉不太灵活，关键字只能从第⼀个字符开始匹配，不能实现任意位置的匹配和多个关键字的匹配；另外⼀⼀种⽅法是重写listbox 感觉太复杂……
  最后我⾃⼰想了个⽐较简单，灵活的⽅法：
  使⽤listBox的DrawMode.OwnerDrawFixed属性，设置ItemHeight=30，添加listBox1_DrawItem事件
代码
private static readonly string ConnectionString = ConfigurationManager.ConnectionStrings["SQLConnString"].ConnectionString;
private void Form1_Load(object sender, EventArgs e)
{
listBox1.DrawMode = DrawMode.OwnerDrawFixed;
listBox1.ItemHeight = 30;
}
代码
private void listBox1_DrawItem(object sender, DrawItemEventArgs e)
{
// Set the DrawMode property to draw fixed sized items.
listBox1.DrawMode = DrawMode.OwnerDrawFixed;
// Draw the background of the ListBox control for each item.
e.DrawBackground();
// Define the default color of the brush as black.
Brush myBrush = Brushes.Black;
FontFamily fontFamily = new FontFamily("宋体");
System.Drawing.Font myFont = new Font(fontFamily, 20);
// Determine the color of the brush to draw each item based on the index of the item to draw .
if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
{
//e.Graphics.FillRectangle(Brushes.Blue, e.Bounds);
if (e.Index > -1)
{
e.Graphics.DrawString(listBox1.Items[e.Index].ToString(), myFont, Brushes.White, e.Bounds, StringFormat.GenericDefault);
}
}
else
{
//e.Graphics.FillRectangle(Brushes.White, e.Bounds);
if (e.Index > -1)
{
e.Graphics.DrawString(listBox1.Items[e.Index].ToString(), myFont, myBrush, e.Bounds, StringFormat.GenericDefault);
}
}
e.DrawFocusRectangle();
}
以SQL Server2005⽰例数据库AdventureWorks为例，添加textBox1_TextChanged事件，获取输⼊关键字，通过模糊查询将数据库中的
相关信息绑定到下拉框listBox1中：
代码
private void BindList(DataTable dt)
{
this.listBox1.Items.Clear();
for (int i = 0; i < dt.Rows.Count; i++)
{
listBox1.Items.Add(dt.Rows[i]["name"].ToString());
}
if (dt.Rows.Count < 11)
{
this.listBox1.Height = 30 * dt.Rows.Count + 30;
}
else
{
this.listBox1.Height = 300;
}
this.listBox1.Visible = true;
}
private DataTable getDataTable(string s)
{
string sql = @" SELECT Name FROM  Person.CountryRegion where [Name] like '%" + s.Trim() + "%' ";
string strErr = "";
DataTable dt = new DataTable();
RunSQL(sql, null, out dt, out strErr);
return dt;
}
public static bool RunSQL(string strSQL, SqlParameter[] para, out DataTable objDataTable, out string strErr)
{
objDataTable = new DataTable();
strErr = "";
using (SqlConnection conn = new SqlConnection(ConnectionString))
{
SqlCommand sqlComm = new SqlCommand(strSQL, conn);
sqlComm.CommandType = CommandType.Text;
if (para != null)
{
foreach (SqlParameter parm in para)
{
if ((parm.Direction == ParameterDirection.InputOutput || parm.Direction == ParameterDirection.Input) &&                                (parm.Value == null))
{
parm.Value = DBNull.Value;
}
sqlComm.Parameters.Add(parm);
}
}
SqlDataAdapter sqlDa = new SqlDataAdapter();
try
{
sqlDa.SelectCommand = sqlComm;
sqlDa.Fill(objDataTable);
sqlComm.Parameters.Clear();
return true;
}
catch (Exception ex)
{
strErr = ex.Message;
return false;
}
finally
{
if (sqlComm != null)
{
sqlComm.Dispose();
}
if (sqlDa != null)
{
sqlDa.Dispose();
}
}
}
}
private void textBox1_TextChanged(object sender, EventArgs e)
{
if (Box1.Text.Trim() != "")
{
DataTable dt = Box1.Text.Trim());
BindList(dt);
this.listBox1.Visible = true;
}
else
{
this.listBox1.Items.Clear();
this.listBox1.Visible = false;
}
}
在listBox1显⽰关键字的匹配结果时，先将 this.listBox1.Visible = false；当有匹配结果时置为true，就可以实现当关键字有匹配项时出现下拉提⽰，没有时隐藏，然后定义listbox和textbox的⿏标事件，使⿏标经过时变⾊，效果就跟百度的下拉提⽰⼀样了
代码
private void listBox1_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Enter && this.listBox1.Visible && this.listBox1.SelectedItems.Count > 0)
{
this.listBox1.Visible = false;
}
}
private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Down && this.listBox1.Visible)
{
this.listBox1.Focus();
if (this.listBox1.SelectedItems.Count > 0)
{
this.listBox1.SetSelected(this.listBox1.SelectedIndex, false);
}
mousemove是什么键if (this.listBox1.Items.Count > 0)
{
this.listBox1.SetSelected(0, true);
}
}
}
private void listBox1_MouseUp(object sender, MouseEventArgs e)
{
if (this.listBox1.SelectedItems.Count > 0)
{
this.listBox1.Visible = false;
}
}
private void listBox1_MouseMove(object sender, MouseEventArgs e)
{
Point m = new Point(e.X, e.Y);
int index = GetItemAt(this.listBox1, e.X, e.Y);
if (this.listBox1.SelectedItems.Count > 0 && this.listBox1.SelectedIndex != index)            {
this.listBox1.SetSelected(this.listBox1.SelectedIndex, false);
}
if (index != -1 && this.listBox1.SelectedIndex != index)
{
this.listBox1.SetSelected(index, true);
}
}
private int GetItemAt(ListBox listBox, int X, int Y)
{
int index = -1;
for (int i = 0; i < listBox.Items.Count; i++)
{
System.Drawing.Rectangle r = listBox.GetItemRectangle(i);
if (r.Contains(new Point(X, Y)))
{
index = i;
break;
}
}
return index;
}
最后的效果：

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