timer居然死掉一般?!

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;namespace TIMER
{
/// <summary>
/// Summary description for Form1.
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.Timer timer1;
private System.Windows.Forms.Label label1;
private System.Windows.Forms.Button button1;
private System.ComponentModel.IContainer components; public Form1()
{
//
// Required for Windows Form Designer support
//
InitializeComponent(); //
// TODO: Add any constructor code after InitializeComponent call
//
} /// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null) 
{
components.Dispose();
}
}
base.Dispose( disposing );
} #region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.components = new System.ComponentModel.Container();
this.timer1 = new System.Windows.Forms.Timer(this.components);
this.label1 = new System.Windows.Forms.Label();
this.button1 = new System.Windows.Forms.Button();
this.SuspendLayout();
// 
// timer1
// 
this.timer1.Tick += new System.EventHandler(this.timer1_Tick);
// 
// label1
// 
this.label1.Location = new System.Drawing.Point(16, 24);
this.label1.Name = "label1";
this.label1.Size = new System.Drawing.Size(224, 24);
this.label1.TabIndex = 0;
this.label1.Text = "label1";
// 
// button1
// 
this.button1.Location = new System.Drawing.Point(16, 152);
this.button1.Name = "button1";
this.button1.Size = new System.Drawing.Size(88, 40);
this.button1.TabIndex = 1;
this.button1.Text = "button1";
this.button1.Click += new System.EventHandler(this.button1_Click);
// 
// Form1
// 
this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
this.ClientSize = new System.Drawing.Size(288, 206);
this.Controls.Add(this.button1);
this.Controls.Add(this.label1);
this.Name = "Form1";
this.Text = "Form1";
this.Load += new System.EventHandler(this.Form1_Load);
this.Closed += new System.EventHandler(this.Form1_Closed);
this.ResumeLayout(false); }
#endregion /// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main() 
{
Application.Run(new Form1());
} private void timer1_Tick(object sender, System.EventArgs e)
{
this.label1.Text = System.DateTime.Now.ToString( "yyyy-MM-dd HH:mm:ss" );
} private void Form1_Load(object sender, System.EventArgs e)
{
this.timer1.Enabled = true;
} private void Form1_Closed(object sender, System.EventArgs e)
{
this.timer1.Enabled = false;
} private void button1_Click(object sender, System.EventArgs e)
{
//do something
}
}
}//如果在处理button1_Click过程中要耗时太长, timer事件好象死了一般(lable1.Text无变化). 为何?如果另外开一线程启动timer_Click,根本启动不了! 为何?(同样地lable1.Text无变化)