Winform单例窗体

using System;
using System.Collections.Generic;
using System.Windows.Forms;
using System.Text;
namespace Common
{
    /// <summary>
    /// 窗体的单例模式
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class FormSingle<T> where T : Form, new()
    {
        private static T form;
        private static IList<T> list { get; set; }
        public static T GetForm(T t1)
        {
            //检查是否存在窗体
            if (!IsExist(t1))
            {
               CreateNewForm(t1);
            }
            return form;
        }
        /// <summary>释放对象
        /// </summary>
        /// <param name="obj"></param>
        /// <param name="args"></param>
        private static void Display(object obj, FormClosedEventArgs args)
        {
            form = null;
            list.Remove(form);
        }
        /// <summary>创建新窗体
        /// </summary>
        private static void CreateNewForm(T t1)
        {
            form = t1;
            form.FormClosed += new FormClosedEventHandler(Display);//订阅窗体的关闭事件，释放对象
        }
        /// <summary>
        /// 是否存在该窗体
        /// </summary>
        /// <param name="T1"></param>
        /// <returns></returns>
        private static bool IsExist(T T1)
        {
            if (list == null)
            {
                list=new List<T>();
                list.Add(T1);
                return false;
            }
            //如果窗体的文本相同则认为是同一个窗体
            foreach (var t in list)
            {
                if (t.Text == T1.Text)
                    return true;
            }
            list.Add(T1);
            return false;
        }
    }
}

调用如下：

  
不带参数的构造函数  
Customer.AddCustomer customer = Common.FormSingle<Customer.AddCustomer>.GetForm(new Customer.AddCustomer());
            customer.MdiParent = this;//Mdi窗体
            customer.WindowState = FormWindowState.Maximized;//最大化
            customer.Show();
            customer.Activate();
带参数的构造函数
  Customer.AddCustomer customer = Common.FormSingle<Customer.AddCustomer>.GetForm(new Customer.AddCustomer(customerid));
            customer.MdiParent = this;
            customer.WindowState = FormWindowState.Maximized;
            customer.Show();
            customer.Activate();