C#怎样保证弹出窗体是唯一并居中显示

Winform窗体中，假如我从Form1窗体要弹出Form2窗体，写法是这样的：

Form2 f2 = new Form2();

f2.Show();

1、如何使窗体打开时居中显示

 //初始化默认窗体居中显示

Form2 f2 = new Form2();
f2.StartPosition = FormStartPosition.CenterScreen;

f2.Show();

2、如何实现弹出子窗口的不关闭时，其它的窗口无法操作

 Form2 f2 = new Form2();
 f2.StartPosition = FormStartPosition.CenterScreen;

 f2.ShowDialog()；

3、如何保证打开窗体是唯一的（是通过show()打开）

例子如下：

1、窗体页面

1）Form1页面

2）Form2页面

 

2、页面源码

1）Form1页面源码

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

namespace TestWinForm
{
    public partial class Form1 : Form
    {
        //创建全局变量，用来存放已show出的窗体对象
        List<Form> allforms = new List<Form>();

        public Form1()
        {
            InitializeComponent();
            //初始化默认居中显示
            this.StartPosition = FormStartPosition.CenterScreen;
        }

        /// <summary>
        /// 普通方式（通过直接show出来）
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnOpen_Click(object sender, EventArgs e)
        {
            if (this.txtAddMsg.Text == "") {
                MessageBox.Show("输入信息文本不能为空");
                return;
            }
            string msg = this.txtAddMsg.Text;
            //实例化对象
            Form2 f2 = new Form2(this);
            //居中显示
            f2.StartPosition = FormStartPosition.CenterScreen;
            //打开窗体
            f2.Show();
        }

        /// <summary>
        /// 特殊方式（通过onlyoneForm()方法处理）
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnOpen1_Click(object sender, EventArgs e)
        {
            if (this.txtAddMsg.Text == "")
            {
                MessageBox.Show("输入信息文本不能为空");
                return;
            }
            string msg = this.txtAddMsg.Text;
            //实例化对象
            Form2 f2 = new Form2(this,msg);
            //设置居中显示
            f2.StartPosition = FormStartPosition.CenterScreen;
            //验证并保证窗体唯一
            onlyoneForm(f2);
        }

        #region  保证窗体唯一方法

        /// <summary>
        /// 显示唯一的窗体
        /// </summary>
        /// <param name="FF"></param>
        private void onlyoneForm(Form FF)
        {
            //判断窗体是否已经弹出，默认false
            bool hasform = false;
            //遍历所有窗体对象
            foreach (Form f in allforms)
            {
                //判断弹出的窗体是否重复
                if (f.Name == FF.Name)
                {
                    //重复，修改为true
                    hasform = true;
                    f.WindowState = FormWindowState.Normal;
                    //获取焦点
                    f.Focus();
                }
            }
            if (hasform)
            {
                FF.Close();
            }
            else
            {
                //添加到所有窗体中
                allforms.Add(FF);
                //并打开该窗体
                FF.Show();
            }
        }

        /// <summary>
        /// 移除窗体对象
        /// </summary>
        /// <param name="f"></param>
        public void RemoveForm(Form f)
        {
            if (allforms.Contains(f))
            {
                allforms.Remove(f);
            }
        }

        #endregion
    }
}

2）Form2页面源码

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

namespace TestWinForm
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        //保存传递的窗体对象
        Form1 form1 = null;

        public Form2(Form1 f1) {
            InitializeComponent();
            form1 = f1;
        }
        
        public Form2(Form1 f1, string msg) {
            InitializeComponent();
            form1 = f1;
            this.txtShowMsg.Text = msg;
        }

        /// <summary>
        /// 移除窗体对象
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Form2_FormClosing(object sender, FormClosingEventArgs e)
        {
            form1.RemoveForm(this);
        }
    }
}

 

3、结果视图页面

1）普通方式结果

2）特殊方式结果

 参考来源：

http://www.mamicode.com/info-detail-1375089.html

http://www.cnblogs.com/sunshuping/p/5850799.html