C#刷新问题 连接未打开

Question

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.Data.SqlClient;namespace NewsManagerSys
{
    public partial class FrmMain : Form
    {
        DataSet ds = new DataSet();
         static string strSql = "Data Source=.;Initial Catalog=NewsManagerSys;Integrated Security=True";
        SqlConnection conn = new SqlConnection(strSql);        public FrmMain()
        {
            InitializeComponent();
        }        //窗体加载
        private void FrmMain_Load(object sender, EventArgs e)
        {
            Quanbu();  //窗体运行显示全部新闻信息            
        }        //窗体运行显示全部新闻信息
        #region 填充Fill
        private void Quanbu()
        {
          
                if (ds.Tables["News"] != null)
                {
                    ds.Tables["News"].Clear();
                }
                string str = "select Id,title,begintime,author from News order by id desc";
                DataSet result = DBHelper.DataMuster(str, "News");
                      
                dgvNews.DataSource = result.Tables["News"];
                
          
            //try
            //{
                
            //    SqlDataAdapter sda = new SqlDataAdapter("select Id,title,begintime,author from News order by id desc", conn);            //    //try
            //    //{
            //    sda.Fill(ds, "News");            //}              //}
            //catch (Exception ex)
            //{            //    MessageBox.Show(ex.Message);
            //}
            //this.dgvNews.DataSource = ds.Tables["News"];
        }
        #endregion
       
        private void dgvNews_SelectionChanged(object sender, EventArgs e)
        {
            if (this.dgvNews.SelectedRows.Count > 0)
            {
                this.txtTitle.Text = dgvNews.CurrentRow.Cells["title"].Value.ToString();
                this.txtbegintime.Text = dgvNews.CurrentRow.Cells["begintime"].Value.ToString();
                this.txtauthor.Text = dgvNews.CurrentRow.Cells["author"].Value.ToString();                //新闻内容
                try
                {
                    conn.Open();  //打开数据库连接                    int id = Convert.ToInt32(this.dgvNews.SelectedRows[0].Cells["Id"].Value);                    string sql = string.Format("select * from News where id={0}",id);
                    SqlCommand comm = new SqlCommand(sql,conn);
                    SqlDataReader reader = comm.ExecuteReader(CommandBehavior.CloseConnection);
                    while(reader.Read())
                    {
                        this.txtContent.Text = reader["content"].ToString();
                    }
                    reader.Close();//已关               
                }
                catch (Exception)
                {
                    MessageBox.Show("数据连接失败！");
                }
            }
        }
       
        //增加信息
        private void btnzhengjia_Click(object sender, EventArgs e)
        {
            if ((this.txtTitle.Text == string.Empty) ||(this.txtContent.Text == string.Empty) || (this.txtauthor.Text == string.Empty))
            {
                MessageBox.Show("新闻标题，内容和作者均不能为空！", "提示", MessageBoxButtons.OK);
            }
            else
            {
                NewsInsert();  //新增新闻信息
                Quanbu();
            }
        }        //新增新闻信息
        private void NewsInsert()
        {
            try
            {
                if (conn.State == ConnectionState.Closed)
                {
                    conn.Open();   //打开数据库连接
                }
                
               
                string sql = string.Format("insert News(title,content,begintime,author)values('{0}','{1}',default,'{2}')", this.txtTitle.Text, this.txtContent.Text, this.txtauthor.Text);
                SqlCommand comm = new SqlCommand(sql, conn);
                int i = comm.ExecuteNonQuery();
                if (i == 1)
                {
                    
                    MessageBox.Show("录入成功！");
                    Quanbu();  //窗体运行显示全部新闻信息
                }
                else
                {
                    MessageBox.Show("录入失败！");
                }            }            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);            }
            finally
            {
                conn.Close();  //关闭数据库连接
            }
        }        //执行关闭按钮
        private void btnExit_Click(object sender, EventArgs e)
        {
            DialogResult result = MessageBox.Show("是否要退出？","提示",MessageBoxButtons.YesNo);
            if (result == DialogResult.Yes)
            {
                Application.Exit();   //退出当前窗体
            }
        }        private void dgvNews_SelectionChanged_1(object sender, EventArgs e)
        {
            if (this.dgvNews.SelectedRows.Count > 0)
            {
                this.txtTitle.Text = dgvNews.CurrentRow.Cells["title"].Value.ToString();
                this.txtbegintime.Text = dgvNews.CurrentRow.Cells["begintime"].Value.ToString();
                this.txtauthor.Text = dgvNews.CurrentRow.Cells["author"].Value.ToString();                //新闻内容                conn.Open();  //打开数据库连接                    int id = Convert.ToInt32(this.dgvNews.SelectedRows[0].Cells["Id"].Value);                    string sql = string.Format("select * from News where id={0}", id);
                    SqlCommand comm = new SqlCommand(sql, conn);
                    SqlDataReader reader = comm.ExecuteReader(CommandBehavior.CloseConnection);
                    while (reader.Read())
                    {
                        this.txtContent.Text = reader["content"].ToString();
                    }
                    reader.Close();
                }
             
            }
        }
    }标注颜色的地方是出错的地方：问题
首先窗体加载查询所有的信息显示到datagrideview上，单击增加提示录入成功后，需要刷新datagrideview 就在刷新的时间提示“连接未关闭 连接的状态为打开状态”

Answer 1

 if (i == 1)
                {
                    conn.Close();  //关闭数据库连接
                    MessageBox.Show("录入成功！");
                    Quanbu();  //窗体运行显示全部新闻信息
                }