单例模式演示-2-39-07

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace _02利用单例模式的思想实现窗体只显示一个
{
    public partial class Form2 : Form
    {
        private Form2()
        {
            InitializeComponent();
        }

        private static Form2 _form2Instance;
        private static readonly object syn = new object();
        public static Form2 GetInstance()
        {
            if (_form2Instance == null || _form2Instance.IsDisposed)
            {
                lock (syn)
                {
                    if (_form2Instance == null || _form2Instance.IsDisposed)
                    {
                        _form2Instance = new Form2();
                    }
                }
                
            }
            return _form2Instance;
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace _02利用单例模式的思想实现窗体只显示一个
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        //Form2 f2 = null;
        private void button1_Click(object sender, EventArgs e)
        {
            //if (f2 == null || f2.IsDisposed)
            //{
            //    f2 = new Form2(); f2.Show();
            //}
            //else
            //{
            //    f2.Activate();
            //}
            Form2 f2 = Form2.GetInstance();
            f2.Show();


        }
    }
}