WinFrom 执行打开新窗口代码一样，结果却不一样

[Diack]

就是指桌面下面的窗口栏，我点击配置按钮时，会打开多个窗口，当配置存在时，程序自动登录时却不会打开新窗口，打开新窗口的代码一样，一直找不到是什么原因

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;
using System.Configuration;
using System.IO;
using System.Data.SqlClient;

namespace Vote
{
    public partial class SysManage : Form
    {
        public SysManage()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            using (SqlConnection connection = new SqlConnection("server=" + textBox1.Text.Trim() + ";database=vote;uid=" + textBox2.Text.Trim() + ";pwd=" + textBox3.Text.Trim() + ";Connection Timeout=5;"))
            {
                try
                {
                    connection.Open();
                    connection.Close();
                    System.Xml.XmlDocument str1 = new System.Xml.XmlDocument();　　//创建一个xml文档模型
                    str1.Load(Application.StartupPath + @"\Config.xml");　　　　　//加载操作对象

                    System.Xml.XmlNode nodeServer = str1.SelectSingleNode("/Database/Server");　//获得节点
                    System.Xml.XmlNode nodeDatabaseName = str1.SelectSingleNode("/Database/DatabaseName");
                    System.Xml.XmlNode nodeUser = str1.SelectSingleNode("/Database/User");
                    System.Xml.XmlNode nodePassword = str1.SelectSingleNode("/Database/Password");
                    System.Xml.XmlNode nodeMode = str1.SelectSingleNode("/Database/mode");



                    nodeServer.InnerText = textBox1.Text.Trim();　　　　// 为server节点里加文本内容
                    nodeDatabaseName.InnerText = "vote";
                    nodeUser.InnerText = textBox2.Text.Trim();
                    nodePassword.InnerText = textBox3.Text.Trim();
                    str1.Save(Application.StartupPath + @"\Config.xml");　　//保存更新
                    //判断是否是由其他窗口打开，是则退出初始化
                    if (Application.OpenForms["Main"] != null || Application.OpenForms["KeyMain"] != null)
                    {
                        MessageBox.Show("配置修改需要重新启动程序才生效");
                        this.Close();
                    }
                    else
                    {
                        Main from = new Main();
                        from.MdiParent = null;
                        from.ShowDialog();
                        this.Close();
                    }
                }
                catch (System.Data.SqlClient.SqlException E)
                {
                    MessageBox.Show("连接错误，请输入正确的连接参数");
                }
                finally
                {
                    connection.Close();
                }
            }

        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void SysManage_Load(object sender, EventArgs e)
        {

            DataSet ds = new DataSet();
            if (!File.Exists(Application.StartupPath + @"\Config.xml"))
            {
                MessageBox.Show("配置文件损坏,重新安装");
                return;
            }

            ds.ReadXml(Application.StartupPath + @"\Config.xml");    //用dataset读取xml
            string Server = ds.Tables[0].Rows[0]["Server"].ToString().Trim();    //第一行 节点为server的　文本
            string aseName = ds.Tables[0].Rows[0]["DatabaseName"].ToString().Trim();
            string User = ds.Tables[0].Rows[0]["User"].ToString().Trim();
            string Password = ds.Tables[0].Rows[0]["Password"].ToString().Trim();
            string mode = ds.Tables[0].Rows[0]["mode"].ToString().Trim();
            
                textBox1.Text = Server;
                textBox2.Text = User;
                textBox3.Text = Password;
                if (mode == "0")
                {
                    radioButton1.Checked = true;
                    radioButton2.Checked = false;
                }
                else
                {
                    radioButton1.Checked = false;
                    radioButton2.Checked = true;
                }

                using (SqlConnection connection = new SqlConnection("server=" + Server + ";database=" + aseName + ";uid=" + User + ";pwd=" + Password + ";Connection Timeout=5"))
                {
                    try
                    {
                        connection.Open();
                        connection.Close();
                        //判断是否是由其他窗口打开，是则退出初始化
                        if (Application.OpenForms["Main"] != null || Application.OpenForms["KeyMain"] != null)
                        {
                            return;
                        }
                        Main from = new Main();
                        from.ShowDialog();
                        from.MdiParent = null;
                        this.Close();
                    }
                    catch (System.Data.SqlClient.SqlException E)
                    {

                    }
                    finally
                    {
                        connection.Close();
                    }
                }
        }
    }
}

[zjx198934]

1.from.MdiParent = null;
2.from.ShowDialog();
这个两句都应该是from.ShowDialog();先执行！