具有自动完成功能的ComboBox（c#）

根据你输入的内容自动过滤出匹配的列表项，并实时显示出来，和IE地址栏类似。
程序很简单，只是很长事时间没更新blog了，用这篇小文章来更新一下。

程序原理是这样的：组件继承之combobox，并且拥有一个listbox成员，当组件的text改变时，就从combobox中过滤出匹配的列表项，并且把这些列表项加入到listbox中显示出来。
演示效果：
using System;


using System.Collections;


using System.ComponentModel;


using System.Drawing;


using System.Data;


using System.Windows.Forms;





namespace XPangLib


{


/// <summary>


/// AutoComboBox 的摘要说明。


/// </summary>


public class AutoComboBox : System.Windows.Forms.ComboBox


{





private System.Windows.Forms.ListBox lbMain;


/// <summary>


/// 必需的设计器变量。


/// </summary>


private System.ComponentModel.Container components = null;





public AutoComboBox()


{


// 该调用是 Windows.Forms 窗体设计器所必需的。


InitializeComponent();





lbMain = new ListBox() ;


lbMain.Click+=new EventHandler(lbMain_Click);


lbMain.KeyDown+=new KeyEventHandler(lbMain_KeyDown);


lbMain.Visible = false ;


}


/// <summary>


/// 得到匹配给定字符串的列表


/// </summary>


private ArrayList GetFillList(string strValue)


{


ArrayList alReturn = new ArrayList() ;


int iCount = this.Items.Count ;


int iLen = strValue.Length ;





for(int i = 0 ;i < iCount ;i++)


{


string strSelItem = this.Items[i].ToString() ;





if (strSelItem.Length < iLen)


continue ;





if (strSelItem.Substring(0,iLen) == strValue)


alReturn.Add(strSelItem) ;


}





return alReturn ;


}


/// <summary>


/// 清理所有正在使用的资源。


/// </summary>


protected override void Dispose( bool disposing )


{


if( disposing )


{


if( components != null )


components.Dispose();


}


base.Dispose( disposing );


}





#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()


{//


// AutoComboBox


//


this.Sorted = true;


this.KeyDown += new System.Windows.Forms.KeyEventHandler(this.AutoComboBox_KeyDown);


this.dro&#112;Down += new System.EventHandler(this.AutoComboBox_dro&#112;Down);


this.TextChanged += new System.EventHandler(this.AutoComboBox_TextChanged);


this.sel&#101;ctedIndexChanged += new System.EventHandler(this.AutoComboBox_sel&#101;ctedIndexChanged);


this.Leave += new System.EventHandler(this.AutoComboBox_Leave);





}


#endregion





protected override void OnPaint(PaintEventArgs pe)


{


// TODO: 在此添加自定义绘画代码





// 调用基类 OnPaint


base.OnPaint(pe);


}


private void lbMain_Click(object sender, System.EventArgs e)


{


if (lbMain.sel&#101;ctedItems.Count == 0)


return ;


string strSel = lbMain.sel&#101;ctedItem.ToString() ;


this.Text = strSel ;


int iSel = this.FindStringExact(Text) ;


if (iSel != -1)


this.sel&#101;ctedIndex = iSel ;


lbMain.Visible = false ;


}


private void AutoComboBox_TextChanged(object sender, System.EventArgs e)


{


if (Text == "")


{


lbMain.Visible = false ;


return ;


}


if (!this.Parent.Controls.Contains(lbMain))


{


lbMain.Width = this.Width ;


lbMain.Height = 100 ;


lbMain.Parent = this.Parent ;


lbMain.Top = this.Top + this.Height + 1 ;


lbMain.Left = this.Left ;


this.Parent.Controls.Add(lbMain);


lbMain.BringToFront() ;


}


ArrayList alFill = GetFillList(Text) ;


lbMain.Items.Clear() ;


lbMain.Items.AddRange(alFill.ToArray()) ;


if (lbMain.Items.Count > 0)


lbMain.sel&#101;ctedIndex = 0 ;


if (!lbMain.Visible)


lbMain.Visible = true ;


}





private void AutoComboBox_Leave(object sender, System.EventArgs e)


{


if (!lbMain.Focused)


lbMain.Visible = false ;


}





private void AutoComboBox_dro&#112;Down(object sender, System.EventArgs e)


{


lbMain.Visible = false ;


}





private void AutoComboBox_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)


{


if (lbMain.Visible)


{


if (e.KeyCode == Keys.Up||e.KeyCode == Keys.Down||e.KeyCode == Keys.Left||


e.KeyCode == Keys.Right||e.KeyCode == Keys.PageDown||e.KeyCode == Keys.PageUp)


{


lbMain_KeyDown(lbMain,e) ;


e.Handled = true ;


}


else if (e.KeyCode == Keys.Enter)


{


lbMain_Click(lbMain,e) ;


e.Handled = true ;


}


}


}


private void lbMain_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)


{





if (e.KeyCode == Keys.Up||e.KeyCode == Keys.Left||e.KeyCode == Keys.PageUp)


{


if (lbMain.sel&#101;ctedIndex > 0)


lbMain.sel&#101;ctedIndex = lbMain.sel&#101;ctedIndex - 1 ;


}


else if (e.KeyCode == Keys.Down||e.KeyCode == Keys.Right||e.KeyCode == Keys.PageDown)


{


if (lbMain.sel&#101;ctedIndex < lbMain.Items.Count - 1)


lbMain.sel&#101;ctedIndex = lbMain.sel&#101;ctedIndex + 1 ;


}


}





private void AutoComboBox_sel&#101;ctedIndexChanged(object sender, System.EventArgs e)


{


lbMain.Visible = false ;


}


}//end class


}//end namespace


是什么呢?