private void button1_Click(object sender, EventArgs e)
 { 
     string strcom = @"Data Source = (localdb)ProjectModels;Initial Catalog = XSCJDB; Integrated Security = True;";
     SqlConnection sqlcon;
     using (sqlcon = new SqlConnection(strcom))
     {
         sqlcon.Open();
         MessageBox.Show("數(shù)據(jù)庫(kù)連接狀態(tài)" + sqlcon.State.ToString(), "第一個(gè)對(duì)話框");
     }
     MessageBox.Show("數(shù)據(jù)庫(kù)連接狀態(tài)" + sqlcon.State.ToString(), "第二個(gè)對(duì)話框");

 }

  private void button2_Click(object sender, EventArgs e)
  {
      string strcom = @"Data Source = (localdb)ProjectModels;Initial Catalog = XSCJDB; Integrated Security = True;";
      SqlConnection conn =null;
      try
      {
          conn = new SqlConnection(strcom);
          conn.Open();

          SqlCommand mycmm= new SqlCommand();
          mycmm.Connection = conn;

          mycmm.CommandType = CommandType.Text;
          mycmm.CommandText = @"insert into
                             student(Id,name,major,grade,tel)
                             values(@Id,@name,@major,@grade,@tel)";
          mycmm.Parameters.Add(new SqlParameter("@Id", 2022002));
          mycmm.Parameters.Add(new SqlParameter("@name", "李四"));
          mycmm.Parameters.Add(new SqlParameter("@major", "CS"));
          mycmm.Parameters.Add(new SqlParameter("@grade","80"));
          mycmm.Parameters.Add(new SqlParameter("@tel","13999216"));

          int returnvalue=mycmm.ExecuteNonQuery();

          if(returnvalue!=-1)
          {
              MessageBox.Show("數(shù)據(jù)插入成功");
          }
      }
      catch(Exception ex) 
      {
          if(conn != null)
          {
              MessageBox.Show("數(shù)據(jù)插入失敗" + ex.Message);
          }
      }
  }

 // 處理button3的點(diǎn)擊事件，從數(shù)據(jù)庫(kù)中查詢并顯示所有數(shù)據(jù)
 private void button3_Click(object sender, EventArgs e)
 {
     // 數(shù)據(jù)庫(kù)連接字符串
     string strcom = @"Data Source = (localdb)ProjectModels;Initial Catalog = XSCJDB; Integrated Security = True;";
     SqlConnection conn = null;

     try
     {
         // 初始化并打開數(shù)據(jù)庫(kù)連接
         conn = new SqlConnection(strcom);
         conn.Open();

         // 創(chuàng)建并配置SqlCommand對(duì)象
         SqlCommand mycmm = new SqlCommand
         {
             Connection = conn,
             CommandType = CommandType.Text,
             CommandText = @"select * from student"
         };

         // 使用SqlDataAdapter填充DataSet
         SqlDataAdapter sda = new SqlDataAdapter(mycmm);
         DataSet ds = new DataSet();
         sda.Fill(ds, "studentList");

         // 顯示查詢結(jié)果到DataGridView
         dataGridView2.DataSource = ds.Tables["studentList"].DefaultView;

         // 關(guān)閉數(shù)據(jù)庫(kù)連接
         conn.Close();
     }
     catch (Exception ex)
     {
         // 處理異常
         MessageBox.Show(ex.Message);
         if (conn != null)
         {
             conn.Close();
         }
     }
 }

       // 處理button4的點(diǎn)擊事件，根據(jù)名字查詢數(shù)據(jù)
       private void button4_Click(object sender, EventArgs e)
       {
           // 數(shù)據(jù)庫(kù)連接字符串
           string strcon = @"Data Source = (localdb)ProjectModels;Initial Catalog = XSCJDB; Integrated Security = True;";
           SqlConnection myConnection = new SqlConnection(strcon);

           try
           {
               // 打開數(shù)據(jù)庫(kù)連接
               myConnection.Open();

               // 創(chuàng)建并配置SqlCommand對(duì)象
               SqlCommand myCommand = new SqlCommand
               {
                   Connection = myConnection,
                   CommandType = CommandType.Text,
                   CommandText = @"select * from student where name =@name"
               };

               // 添加參數(shù)并賦值
               myCommand.Parameters.Add(new SqlParameter("@name", textBox1.Text));

               // 執(zhí)行查詢命令并檢查結(jié)果
               int res = Convert.ToInt32(myCommand.ExecuteScalar());
               if (res == 0)
               {
                   throw new Exception("查無(wú)此人");
               }

               // 使用SqlDataAdapter填充DataSet
               SqlDataAdapter sda = new SqlDataAdapter(myCommand);
               DataSet ds = new DataSet();
               sda.Fill(ds, "xr");

               // 顯示查詢結(jié)果到DataGridView
               dataGridView2.DataSource = ds.Tables["xr"].DefaultView;

               // 關(guān)閉數(shù)據(jù)庫(kù)連接
               myConnection.Close();
           }
           catch (Exception ex)
           {
               // 處理異常
               MessageBox.Show(ex.ToString());
               if (myConnection != null)
               {
                   myConnection.Close();
               }
           }
       }

// 保存編輯單元格的原始值
object cellTempValue = null;
 
// 單元格開始編輯事件
private void dataGridView2_CellBeginEdit(object sender, DataGridViewCellCancelEventArgs e)
{
    // 保存單元格的原始值
    cellTempValue = this.dataGridView2.Rows[e.RowIndex].Cells[e.ColumnIndex].Value;
}
 
// 單元格結(jié)束編輯事件
private void dataGridView2_CellEndEdit(object sender, DataGridViewCellEventArgs e)
{
    // 如果單元格值沒(méi)有改變，返回
    if (object.Equals(cellTempValue, this.dataGridView2.Rows[e.RowIndex].Cells[e.ColumnIndex].Value))
    {
        return;
    }
 
    // 彈出確認(rèn)修改對(duì)話框
    if (MessageBox.Show("是否確定修改，并更新到數(shù)據(jù)庫(kù)", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Question) != DialogResult.OK)
    {
        // 如果取消修改，恢復(fù)原值
        this.dataGridView2.Rows[e.RowIndex].Cells[e.ColumnIndex].Value = cellTempValue;
        return;
    }
 
    // 數(shù)據(jù)庫(kù)連接字符串
    string strcom = @"your string";
    SqlConnection myConnection = new SqlConnection(strcom);
 
    try
    {
        // 打開數(shù)據(jù)庫(kù)連接
        myConnection.Open();
 
        // 創(chuàng)建并配置SqlCommand對(duì)象
        SqlCommand myCommand = new SqlCommand
        {
            Connection = myConnection,
            CommandType = CommandType.Text
        };
 
        // 構(gòu)建更新SQL語(yǔ)句
        string strSql = String.Format(
            "update student set {0}='{1}' where Id='{2}'",
            this.dataGridView2.Columns[e.ColumnIndex].HeaderText, // 當(dāng)前選擇的列名
            this.dataGridView2.Rows[e.RowIndex].Cells[e.ColumnIndex].Value, // 選中單元格修改后的值
            this.dataGridView2.Rows[e.RowIndex].Cells[0].Value // 選中單元格修改前的值
        );
 
        // 設(shè)置命令文本
        myCommand.CommandText = strSql;
 
        // 執(zhí)行更新命令
        int res = myCommand.ExecuteNonQuery();
 
        // 檢查更新是否成功
        if (res == 0)
        {
            throw new Exception("修改失敗");
        }
        else
        {
            MessageBox.Show("修改成功");
        }
 
        // 關(guān)閉數(shù)據(jù)庫(kù)連接
        myConnection.Close();
    }
    catch (Exception ex)
    {
        // 處理異常
        MessageBox.Show(ex.ToString());
        if (myConnection != null)
        {
            myConnection.Close();
        }
    }
}